The Quantum Revolution with Turing Award Winners Charles Bennett and Gilles Brassard

before the invention of these before the invention of these protocols or their protocols or their protocols or their discovery? discovery? Uh, that's a silly Uh, that's a silly question. question. question. Okay, thank you for that Okay, thank you for that , sir. Is this really a , sir. Is this really a , sir. Is this really a silly question? silly question? silly question? Is this an inappropriate Is this an inappropriate Is this an inappropriate question? because I question? because I question? because I feel like if you feel like if you feel like if you take the law as it is take the law as it is take the law as it is like saying like saying this is not my, this is not my this is not my, this is not my favorite stupid favorite stupid favorite stupid question, but it is question, but it is question, but it is like saying: oh, if like saying: oh, if like saying: oh, if the world functions according to the world functions according to the world functions according to laws that are laws that are laws that are mathematical, couldn't it mathematical, couldn't it mathematical, couldn't it be that we are be that we are be that we are just in a just in a just in a computer computer computer simulation of the world? simulation of the world? This isn't really a question, it's in the question, it's in the same vein as whether a same vein as whether a same vein as whether a tree falls tree falls tree falls silently in the forest if no silently in the forest if no silently in the forest if no one hears it. one hears it. Hello friends, Hello friends, thank you Text Control for thank you Text Control for thank you Text Control for sponsoring the show. sponsoring the show. sponsoring the show. The developers are asking a The developers are asking a The developers are asking a new question. Do new question. Do new question. Do we still need we still need we still need third-party libraries third-party libraries third-party libraries if AI can simply if AI can simply if AI can simply generate all the code generate all the code generate all the code for common for common for common interface tasks? interface tasks? interface tasks? Maybe not always, Maybe not always, Maybe not always, but deep but deep but deep functionality is functionality is functionality is different.

different. different. Document editing, Document editing, Document editing, PDF creation, PDF creation, PDF creation, rendering, rendering, rendering, conversion, conversion, conversion, corporate corporate document workflows—this is the document workflows—this is the result of result of result of years of years of years of engineering, engineering, engineering, extensive extensive extensive testing, and testing, and testing, and millions of real-world millions of real-world millions of real-world implementations. AI can implementations. AI can implementations. AI can generate a lot of generate a lot of generate a lot of code, but it can't code, but it can't code, but it can't instantly create instantly create instantly create decades of decades of decades of proven proven document technologies. And TX Control document technologies. And TX Control provides developers with this provides developers with this provides developers with this foundation so you can foundation so you can foundation so you can focus on focus on focus on building your building your building your application, not on application, not on application, not on developing a developing a developing a document engine from scratch. document engine from scratch. document engine from scratch. Learn more at Learn more at Learn more at textcontrol.com. textcontrol.com. textcontrol.com. Hi, I'm Scott Hi, I'm Scott Hi, I'm Scott Hanselman, and this is Hanselman, and this is Hanselman, and this is another episode of Hansel another episode of Hansel another episode of Hansel Minutes. Today we Minutes. Today we Minutes. Today we have the pleasure of have the pleasure of have the pleasure of speaking with speaking with speaking with Charles G. Bennett Charles G. Bennett Charles G. Bennett and Jill Brassard. They and Jill Brassard. They and Jill Brassard. They are are are ACM Turing Award winners, and we are ACM Turing Award winners, and we are ACM Turing Award winners, and we are especially honored to be especially honored to be especially honored to be chatting with them on the chatting with them on the chatting with them on the ACM ACM ACM ByteCast podcast. Thank you both ByteCast podcast. Thank you both ByteCast podcast. Thank you both for your time and for for your time and for for your time and for spending it with me spending it with me spending it with me today. Um, is it today. Um, is it today. Um, is it really true that you really true that you really true that you met in met in met in Puerto Rico in 1979, Puerto Rico in 1979, Puerto Rico in 1979, and that, Jill, you were and that, Jill, you were and that, Jill, you were swimming and Charles swimming and Charles swimming and Charles just approached just approached just approached you because he heard you you because he heard you you because he heard you were interested in the same things as were interested in the same things as were interested in the same things as him?

him? That's pretty accurate. Yes. That's pretty accurate. Yes. And the reason he knew this is because And the reason he knew this is because it was happening at a it was happening at a conference. Um, and in the conference. Um, and in the conference. Um, and in the program, Charlie program, Charlie program, Charlie noticed that I would be noticed that I would be noticed that I would be speaking on the last speaking on the last speaking on the last day on cryptography day on cryptography day on cryptography and oracles, which were and oracles, which were and oracles, which were two topics particularly two topics particularly two topics particularly close to his heart. close to his heart. He submitted a paper to the He submitted a paper to the same conference same conference same conference on oracles, and his on oracles, and his on oracles, and his paper was rejected. But paper was rejected. But paper was rejected. But he came anyway, he came anyway, he came anyway, and I remember, I and I remember, I and I remember, I remember him remember him remember him telling me about the telling me about the telling me about the content of that article, content of that article, content of that article, not about it being not about it being not about it being rejected, when we rejected, when we rejected, when we met in '79. I met in '79. I met in '79. I remember at remember at remember at the end of my the end of my the end of my talk, or maybe talk, or maybe talk, or maybe during it, I during it, I during it, I mentioned that the mentioned that the mentioned that the most interesting thing about the most interesting thing about the most interesting thing about the conference was conference was conference was hearing Charlie's idea about hearing Charlie's idea about hearing Charlie's idea about oracles. And I oracles. And I oracles. And I hope there hope there were some on the program committee who were some on the program committee who smiled because I smiled because I smiled because I actually told them actually told them actually told them how wrong they were to how wrong they were to how wrong they were to reject this article, reject this article, reject this article, even though I didn't even know it had been even though I didn't even know it had been even though I didn't even know it had been rejected or rejected or rejected or submitted.

submitted. submitted. So, you both So, you both So, you both correct me correct me correct me if I'm wrong, but if I'm wrong, but if I'm wrong, but you've come at this you've come at this you've come at this from different angles. You from different angles. You from different angles. You know Charles from know Charles from know Charles from information physics, and information physics, and information physics, and I know him from computer I know him from computer I know him from computer science and science and science and cryptography. Is this a cryptography. Is this a cryptography. Is this a situation where situation where situation where the difference in your the difference in your the difference in your experiences is experiences is experiences is necessary because necessary because necessary because you can see things you couldn't you can see things you couldn't see alone, and see alone, and together you are better than the together you are better than the together you are better than the sum of your parts? sum of your parts? sum of your parts? Certainly. This is a Certainly. This is a Certainly. This is a great example of great example of great example of interdisciplinary interdisciplinary interdisciplinary research, and what research, and what research, and what we did was the we did was the we did was the result of result of result of not just two people coming together, but not just two people coming together, but not just two people coming together, but two fields: two fields: two fields: computer science and computer science and computer science and cryptography on my cryptography on my cryptography on my part, and physics and part, and physics and part, and physics and information physics on information physics on information physics on Charlie's part. This is Charlie's part. This is Charlie's part. This is actually because these actually because these actually because these two branches two branches two branches met in the ocean at met in the ocean at met in the ocean at San Juan, Puerto San Juan, Puerto Rico. It was the coming together of Rico. It was the coming together of Rico. It was the coming together of these industries, not just these industries, not just these industries, not just people, that made all of this people, that made all of this people, that made all of this possible. Charles, what did possible. Charles, what did possible. Charles, what did you see in him you see in him you see in him that made you that made you that made you think, "This is exactly the think, "This is exactly the think, "This is exactly the person I person I person I need to talk to about this need to talk to about this need to talk to about this "? This is a "? This is a "? This is a person who understands the person who understands the person who understands the essence. essence.

essence. Well, nothing at first. I Well, nothing at first. I , as he noted, , as he noted, , as he noted, reminded him of my reminded him of my reminded him of my article, I think it was the same one article, I think it was the same one article, I think it was the same one , about random , about random , about random oracles, right? oracles, right? This is true. It was This is true. It was rejected, and later rejected, and later rejected, and later it turned it turned it turned into a pretty worthwhile into a pretty worthwhile into a pretty worthwhile paper, I think, with paper, I think, with paper, I think, with another person another person another person I hadn't met before the I hadn't met before the I hadn't met before the conference—John conference—John conference—John Gill, who became Gill, who became Gill, who became my co-author. But my co-author. But my co-author. But I told him about I told him about I told him about it, but... What's important about it, but... What's important about it, but... What's important about this meeting, which this meeting, which this meeting, which also highlights also highlights also highlights the interaction between two the interaction between two the interaction between two fields that fields that fields that were much more were much more were much more separated then than they are separated then than they are separated then than they are now, is that I now, is that I now, is that I told him about something told him about something that I had known for almost 20 that I had known for almost 20 that I had known for almost 20 years, which seemed like years, which seemed like years, which seemed like just an interesting just an interesting just an interesting quirk about how quirk about how information behaves. And he information behaves. And he said, "This is important, said, "This is important, said, "This is important, this has to do with ideas this has to do with ideas this has to do with ideas in cryptography that in cryptography that in cryptography that I haven't heard of." And he I haven't heard of." And he I haven't heard of." And he added, "You know, what added, "You know, what added, "You know, what you're you're you're telling me, if it's telling me, if it's telling me, if it's true, we true, we true, we should write an article about it should write an article about it should write an article about it ." So I kind of ." So I kind of ." So I kind of waited and waited and waited and told told told people about it every now and then. Is people about it every now and then. Is people about it every now and then. Is n't that an interesting thing, even n't that an interesting thing, even n't that an interesting thing, even if I didn't if I didn't if I didn't take it too take it too take it too seriously myself?

seriously myself? seriously myself? Okay, Okay, Okay, so he was the first so he was the first so he was the first computer computer computer scientist. scientist. scientist. Let me interrupt, Let me interrupt, Let me interrupt, if I may. Sorry. Well if I may. Sorry. Well , the main reason , the main reason , the main reason I was the first I was the first I was the first person who was person who was person who was interested in your interested in your interested in your trying to get trying to get trying to get these ideas out to so many people is these ideas out to so many people is these ideas out to so many people is because everyone because everyone because everyone else was a physicist. else was a physicist. The others were me. The others were me. He always said that the others were He always said that the others were physicists. He says physicists. He says physicists. He says you were running around you were running around you were running around telling everyone about telling everyone about telling everyone about your ideas, but the people your ideas, but the people your ideas, but the people I talked to I talked to I talked to thought it was interesting thought it was interesting thought it was interesting physics, but they didn't physics, but they didn't physics, but they didn't think think they were going back to they were going back to their day their day their day jobs doing jobs doing jobs doing other kinds of physics, other kinds of physics, other kinds of physics, right? So bringing right? So bringing right? So bringing computer science computer science computer science into this, uh, makes into this, uh, makes into this, uh, makes a difference, which makes me a difference, which makes me a difference, which makes me think, and I'm not a think, and I'm not a think, and I'm not a theorist. My degree is theorist. My degree is theorist. My degree is not in computer not in computer not in computer science, but rather in science, but rather in science, but rather in software engineering software engineering , and I sometimes have a hard time , and I sometimes have a hard time , and I sometimes have a hard time combining the theoretical combining the theoretical combining the theoretical with the practical. And I don't with the practical. And I don't with the practical. And I don't understand the leap understand the leap understand the leap or the work that or the work that or the work that goes into goes into goes into basic basic basic research and research and research and how it translates how it translates how it translates into something that impacts into something that impacts into something that impacts my daily my daily my daily life. And I know that you life. And I know that you life. And I know that you both care deeply about both care deeply about the importance of the importance of basic basic basic research; research; research; You, especially, think that You, especially, think that You, especially, think that basic basic basic research is something research is something research is something we can we can we can overlook overlook overlook if we're not if we're not if we're not careful. Is that careful. Is that careful. Is that correct?

correct? Well, not necessarily, Well, not necessarily, but it's something that needs to be but it's something that needs to be but it's something that needs to be encouraged and encouraged and encouraged and funded, because funded, because funded, because you know, innovation you know, innovation you know, innovation and what happens and what happens and what happens in practical life in practical life in practical life is the end of the pipeline, is the end of the pipeline, is the end of the pipeline, and the pipeline has several and the pipeline has several and the pipeline has several stages, including stages, including stages, including marketing, innovation, marketing, innovation, marketing, innovation, and many more. But and many more. But and many more. But this pipeline this pipeline this pipeline begins with begins with begins with fundamental fundamental fundamental research. By which research. By which research. By which I mean I mean I mean research research research driven by curiosity by driven by curiosity by driven by curiosity by people who have no people who have no people who have no reason to reason to reason to believe it will ever be believe it will ever be useful for anything. Research Research whose sole purpose is to understand whose sole purpose is to understand whose sole purpose is to understand nature, and then, nature, and then, nature, and then, perhaps, they will perhaps, they will perhaps, they will forever remain forever remain forever remain useless from a practical useless from a practical useless from a practical point of view, or, point of view, or, point of view, or, perhaps, perhaps, perhaps, completely completely completely unforeseen unforeseen unforeseen applications will appear applications will appear applications will appear many years later. And the many years later. And the many years later. And the best example of best example of best example of this is the development of this is the development of this is the development of the theory of relativity the theory of relativity the theory of relativity by Einstein and by Einstein and by Einstein and quantum theory by quantum theory by quantum theory by Bohr and others in the Bohr and others in the Bohr and others in the early 20th century.

early 20th century. These people conducted These people conducted research solely for research solely for research solely for the sake of understanding the sake of understanding the sake of understanding nature, and they had nature, and they had nature, and they had absolutely no absolutely no absolutely no idea that idea that idea that in a few in a few in a few decades, the entire decades, the entire decades, the entire society would be society would be society would be completely completely completely transformed by transformed by transformed by their discoveries. their discoveries. their discoveries. We wouldn't have We wouldn't have We wouldn't have computers today. I computers today. I computers today. I don't mean don't mean don't mean electronic electronic electronic computers without computers without computers without an understanding of quantum an understanding of quantum an understanding of quantum mechanics, and in fact mechanics, and in fact mechanics, and in fact quantum theory is quantum theory is quantum theory is present in almost present in almost present in almost every gadget every gadget every gadget you have in your you have in your you have in your life today. And life today. And life today. And again, without this again, without this again, without this fundamental fundamental fundamental research, which had no research, which had no practical purpose, we would practical purpose, we would not be here today not be here today not be here today . We wouldn't . We wouldn't . We wouldn't talk at a talk at a talk at a distance. So distance. So distance. So basic basic basic research is research is research is absolutely absolutely absolutely necessary for necessary for necessary for science to science to science to develop and for develop and for practical practical applications to emerge, although applications to emerge, although applications to emerge, although not always, but you not always, but you not always, but you never know in never know in never know in advance, so you have to advance, so you have to advance, so you have to continue regardless continue regardless continue regardless .

. I think the part I want to I want to emphasize is emphasize is emphasize is that, uh, the that, uh, the reason they have to be reason they have to be curiosity-driven curiosity-driven is because if you're is because if you're is because if you're trying to make the trying to make the trying to make the basic discoveries that are basic discoveries that are basic discoveries that are necessary to necessary to necessary to create something create something create something specific, you're probably specific, you're probably specific, you're probably going to miss going to miss going to miss something that's going to something that's going to something that's going to be important in the end. be important in the end. Interesting. In other Interesting. In other words, that's why words, that's why words, that's why understanding...of course understanding...of course understanding...of course there are engineering there are engineering there are engineering problems, for example, problems, for example, problems, for example, I know that at IBM one I know that at IBM one I know that at IBM one of the problems was of the problems was of the problems was electroplating, electroplating, electroplating, which they solved which they solved which they solved by using copper by using copper by using copper instead of aluminum. instead of aluminum. So, there they So, there they tried to solve tried to solve tried to solve the problem and did the problem and did the problem and did applied applied applied research to research to research to solve it. But solve it. But solve it. But the examples that the examples that the examples that Gill gave, and many others...

Gill gave, and many others... you could say that you could say that you could say that number theory was number theory was number theory was invented by invented by invented by people like Fermat, and it was people like Fermat, and it was people like Fermat, and it was long considered long considered long considered one of the most useless one of the most useless one of the most useless branches of mathematics, branches of mathematics, branches of mathematics, but its but its but its applications... applications... and it was called the and it was called the queen of mathematics queen of mathematics . . . Queen of mathematics Queen of mathematics . So why the queen? . So why the queen? Because number theory Because number theory was very beautiful and was very beautiful and was very beautiful and completely useless. That's completely useless. That's completely useless. That's why she was called the why she was called the why she was called the queen of mathematics queen of mathematics . And then, of course, . And then, of course, . And then, of course, number theory became number theory became number theory became central to central to central to cryptography with cryptography with the invention of RSA and the the invention of RSA and the Diffie- Diffie- Gellman algorithm in the mid-1970s. Now all of this will Gellman algorithm in the mid-1970s. Now all of this will Gellman algorithm in the mid-1970s. Now all of this will fall apart when fall apart when fall apart when we get a we get a we get a quantum computer. Yet quantum computer. Yet for half a for half a century, this useless century, this useless century, this useless number theory has been number theory has been number theory has been central to central to central to attempts, unfortunately attempts, unfortunately attempts, unfortunately futile attempts, futile attempts, futile attempts, to protect our to protect our to protect our privacy. privacy. Mm. I understand that you Mm. I understand that you both agree that both agree that both agree that finding things that don't finding things that don't finding things that don't necessarily have necessarily have necessarily have practical practical practical applications is applications is applications is important. Just important. Just important. Just research, because research itself research, because research itself matters. Do you matters. Do you think that there is a think that there is a think that there is a problem that I'm problem that I'm problem that I'm trying to solve - this is trying to solve - this is one type of one type of one type of research. I research. I research. I have identified the problem and am have identified the problem and am have identified the problem and am going to move away going to move away going to move away from it in the opposite from it in the opposite from it in the opposite direction. And there's also direction. And there's also direction. And there's also pulling the thread out of the pulling the thread out of the pulling the thread out of the sweater, I don't know. I sweater, I don't know. I sweater, I don't know. I want to pull the want to pull the want to pull the thread of the universe and thread of the universe and thread of the universe and see what's on the see what's on the see what's on the other side. I'm other side. I'm other side. I'm curious, Gil, how you curious, Gil, how you curious, Gil, how you approach this? Are you approach this? Are you approach this? Are you more of a researcher or are more of a researcher or are more of a researcher or are you more of a you more of a you more of a problem solver? Both.

problem solver? Both. problem solver? Both. In both directions. In In both directions. In In both directions. In both directions. Sometimes both directions. Sometimes both directions. Sometimes I have a I have a I have a problem that I problem that I problem that I find really interesting, find really interesting, find really interesting, I work on it, I I work on it, I I work on it, I get my get my get my students to work students to work students to work with me, and sometimes we with me, and sometimes we with me, and sometimes we manage to find manage to find manage to find the answer, and sometimes we don't. the answer, and sometimes we don't. But in other cases, But in other cases, for my for my for my most important most important most important discoveries with Charlie and discoveries with Charlie and discoveries with Charlie and others, it was complete others, it was complete others, it was complete coincidence. We were coincidence. We were coincidence. We were n't looking for anything, and n't looking for anything, and n't looking for anything, and it just fell it just fell it just fell into our hands, like quantum into our hands, like quantum into our hands, like quantum teleportation. We didn't teleportation. We didn't teleportation. We didn't try try try to solve, we didn't to solve, we didn't to solve, we didn't try to find a try to find a try to find a way to do what is way to do what is way to do what is now known as now known as now known as teleportation, because of teleportation, because of course that's impossible course that's impossible . We were working on . We were working on . We were working on something else, and something else, and something else, and the solution that came up the solution that came up the solution that came up for another problem for another problem for another problem was, oh, this is the invention of was, oh, this is the invention of was, oh, this is the invention of quantum quantum quantum teleportation, so it's a teleportation, so it's a teleportation, so it's a complete coincidence, the same complete coincidence, the same complete coincidence, the same with quantum with quantum with quantum cryptography. It cryptography. It cryptography. It was also a was also a was also a coincidence that coincidence that coincidence that Charlie swam up to me Charlie swam up to me , and we started , and we started , and we started talking, and then we talking, and then we talking, and then we started working, and started working, and started working, and ideas were coming up about how to ideas were coming up about how to ideas were coming up about how to proceed, and proceed, and proceed, and more and more more and more more and more interesting ideas were coming up in the interesting ideas were coming up in the interesting ideas were coming up in the direction that we had direction that we had direction that we had initially identified, initially identified, initially identified, but there was no way but there was no way but there was no way I was going to say, "Well, I was going to say, "Well, I was going to say, "Well, let's try to let's try to let's try to find a way to find a way to find a way to use these ideas use these ideas use these ideas for cryptography."

for cryptography." When we, as you said , unraveled the thread, , unraveled the thread, , unraveled the thread, it appeared by it appeared by it appeared by itself. itself. I rely a lot on I rely a lot on chance. chance. chance. But sometimes I have a But sometimes I have a But sometimes I have a favorite problem. I'm favorite problem. I'm favorite problem. I'm working on it, and although it doesn't happen working on it, and although it doesn't happen working on it, and although it doesn't happen very often, I very often, I very often, I manage to find a manage to find a manage to find a solution. Charles, solution. Charles, solution. Charles, some people say some people say some people say when they invent when they invent when they invent something, whether it's a protocol something, whether it's a protocol something, whether it's a protocol or a way of thinking or a way of thinking , that they didn't , that they didn't , that they didn't invent anything. They invent anything. They invent anything. They actually discovered it actually discovered it actually discovered it or discovered it. It was a kind of or discovered it. It was a kind of or discovered it. It was a kind of theory that theory that theory that information information information exists somewhere out there. You exists somewhere out there. You exists somewhere out there. You just need to just need to just need to notice it and then notice it and then notice it and then write it down. Did you two write it down. Did you two write it down. Did you two invent these invent these invent these protocols or protocols or protocols or discover them? discover them? This is a ridiculous This is a ridiculous question. question. question. Okay, thank you for that Okay, thank you for that , sir. Is this really a , sir. Is this really a , sir. Is this really a silly question? silly question? silly question? Is this an inappropriate Is this an inappropriate Is this an inappropriate question? Because I question? Because I question? Because I feel like if you feel like if you feel like if you accept the law, accept the law, accept the law, it's like it's like it's like saying saying this is not my favorite this is not my favorite stupid question, stupid question, stupid question, but it's like but it's like but it's like saying, oh, if the world saying, oh, if the world saying, oh, if the world operates according to operates according to operates according to laws that are laws that are laws that are mathematical, mathematical, mathematical, could it be that we're could it be that we're could it be that we're just in a computer just in a computer just in a computer simulation of the world?

simulation of the world? That's not very smart. That's not very smart. This, this, this question. This, this, this question. This, this, this question. This is in the same series as This is in the same series as This is in the same series as the question of whether a the question of whether a the question of whether a tree falling in tree falling in tree falling in the forest makes no sound the forest makes no sound the forest makes no sound if there is no one around to if there is no one around to hear it. Okay, I agree that the last that the last that the last question is ridiculous, question is ridiculous, question is ridiculous, but not the first. One of but not the first. One of but not the first. One of my favorite pieces of my favorite pieces of my favorite pieces of work deals with work deals with work deals with the issue of simulation. Are the issue of simulation. Are the issue of simulation. Are we living in a we living in a we living in a computer computer computer simulation? And I'm very simulation? And I'm very simulation? And I'm very proud of this paper, proud of this paper, proud of this paper, which I published in the which I published in the Proceedings of the Royal Society. Proceedings of the Royal Society. Proceedings of the Royal Society. Well, why don't you just Well, why don't you just Well, why don't you just say that we say that we say that we live in an equivalence class of a live in an equivalence class of a possible real possible real world and all its world and all its world and all its simulations, and that's all simulations, and that's all simulations, and that's all we can say we can say we can say about it from a scientific about it from a scientific about it from a scientific point of view? point of view? point of view? Unlike Unlike Unlike superposition. superposition. superposition. Unlike what? Unlike what? Unlike what? From superposition. From superposition. From superposition. Yes. Yes. I appreciate both of your I appreciate both of your points of view. When I give points of view. When I give points of view. When I give interviews, I always interviews, I always interviews, I always hope someone hope someone hope someone will say, “Oh, that’s a good will say, “Oh, that’s a good will say, “Oh, that’s a good question. "That's a profound question. "That's a profound question. "That's a profound question." Of course. And question." Of course. And question." Of course. And I think that's a I think that's a I think that's a silly question.

silly question. silly question. You will occasionally You will occasionally You will occasionally get the get the get the opposite opposite opposite reaction from us. reaction from us. reaction from us. Well, you won't know. Well, you won't know. Well, you won't know. You won't know You won't know You won't know until you until you until you watch watch watch it. So, I appreciate it. So, I appreciate it. So, I appreciate your honesty about this your honesty about this . I'm just curious . I'm just curious . I'm just curious because there's a because there's a because there's a huge gap huge gap huge gap between the elegance of between the elegance of between the elegance of quantum quantum quantum information theory in its information theory in its information theory in its theoretical sense theoretical sense theoretical sense and the engineering and the engineering and the engineering required to required to required to implement it at implement it at implement it at scale. And I'm scale. And I'm scale. And I'm trying to understand trying to understand trying to understand how these how these how these jumps happen. Well, I would like to jumps happen. Well, I would like to jumps happen. Well, I would like to draw your draw your draw your attention to something else, attention to something else, attention to something else, namely: beyond namely: beyond namely: beyond looking at things looking at things looking at things simply because they are simply because they are simply because they are interesting. It's fascinating interesting. It's fascinating , , there was something that there was something that attracted me to these attracted me to these attracted me to these questions when I first questions when I first questions when I first heard about them from heard about them from heard about them from my late my late my late colleague and colleague and colleague and classmate, Stephen classmate, Stephen classmate, Stephen Wiesner. Wiesner. Mhm. It seemed Mhm. It seemed intrinsically interesting and intrinsically interesting and intrinsically interesting and immediately caught immediately caught immediately caught my attention. As if to my attention. As if to my attention. As if to indicate that indicate that indicate that the founders of the founders of the founders of information processing, namely information processing, namely information processing, namely Shannon and Turing, Shannon and Turing, missed it. Mhm.

Of course, they Of course, they intentionally left out intentionally left out intentionally left out many things, many things, many things, such as whether such as whether the message was transmitted through the message was transmitted through holes in punched cards holes in punched cards holes in punched cards or by radio waves. But or by radio waves. But what I saw was what I saw was this example of this example of MGM multiplexing. two messages MGM multiplexing. two messages into a form from which into a form from which into a form from which the recipient could the recipient could the recipient could receive one, but receive one, but receive one, but at the same time destroy the at the same time destroy the at the same time destroy the other. And then, of course, he other. And then, of course, he other. And then, of course, he could choose which one to could choose which one to could choose which one to get. That's get. That's get. That's right, I could have chosen any right, I could have chosen any one, and even one, and even one, and even the recipient wouldn't know, the recipient wouldn't know, the recipient wouldn't know, the sender wouldn't know the sender wouldn't know , but...so that , but...so that , but...so that seemed to tell seemed to tell seemed to tell me that the IT guys me that the IT guys me that the IT guys had a huge amount had a huge amount had a huge amount of power. They of power. They of power. They thought that because thought that because thought that because they changed the world, they changed the world, they changed the world, they understood almost everything they understood almost everything they understood almost everything about about about information. And it was a information. And it was a information. And it was a physicist, this colleague of mine, physicist, this colleague of mine, physicist, this colleague of mine, who said, “Well, who said, “Well, who said, “Well, wait a minute.

wait a minute. wait a minute. Some information Some information Some information doesn't behave quite like that doesn't behave quite like that doesn't behave quite like that . You can't . You can't . You can't copy it, or if copy it, or if copy it, or if you try to you try to you try to read it, it will read it, it will read it, it will break it." And one of the break it." And one of the break it." And one of the things you can things you can things you can do with this is do with this is do with this is turn this turn this turn this apparent disadvantage into an apparent disadvantage into an apparent disadvantage into an advantage by creating a kind of advantage by creating a kind of self-destructing multiplex message. Of course, we probably have Of course, we probably have social apps social apps social apps that promise to that promise to that promise to delete delete delete messages after messages after messages after you. Yes. But you you. Yes. But you you. Yes. But you just have to just have to just have to trust them to trust them to trust them to do it. So do it. So do it. So when I first heard about it when I first heard about it when I first heard about it , I said, , I said, , I said, you know, this is a really you know, this is a really you know, this is a really exciting thing about exciting thing about exciting thing about information. I wonder information. I wonder information. I wonder if any information theorists are interested in this if any information theorists are interested in this . I . I tried to explain tried to explain tried to explain it to some people, and it to some people, and it to some people, and a little later a little later a little later Jill and I tried Jill and I tried Jill and I tried to explain it to to explain it to to explain it to quantum optics experts, and quantum optics experts, and quantum optics experts, and they said, "Oh, they said, "Oh, they said, "Oh, you know, you guys you know, you guys you know, you guys just don't understand what you're just don't understand what you're just don't understand what you're talking about." So talking about." So talking about." So there was a certain amount of there was a certain amount of there was a certain amount of arrogance on both arrogance on both arrogance on both sides, which we sides, which we sides, which we helped overcome helped overcome helped overcome when we brought these two when we brought these two when we brought these two areas together. Hi guys, areas together. Hi guys, areas together. Hi guys, this is Scott and I want to this is Scott and I want to this is Scott and I want to welcome one of welcome one of welcome one of our new our new our new sponsors, SERP API. This is the SERP sponsors, SERP API. This is the SERP sponsors, SERP API. This is the SERP API. This is a web search API API. This is a web search API API. This is a web search API that provides that provides that provides developers with developers with developers with structured structured structured access to access to real-time search engine results.

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quantum machine, quantum machine, thinking, "We thought thinking, "We thought thinking, "We thought about this in the '70s, '80s, '90s, and about this in the '70s, '80s, '90s, and about this in the '70s, '80s, '90s, and now I'm seeing it in now I'm seeing it in now I'm seeing it in person." I'm person." I'm person." I'm just curious how you just curious how you just curious how you evaluate this evaluate this evaluate this period of time, and whether period of time, and whether period of time, and whether you managed you managed you managed to work with the to work with the to work with the physical embodiment physical embodiment physical embodiment of what of what of what was only a theory in 1993. was only a theory in 1993. was only a theory in 1993. Well, even better, we Well, even better, we Well, even better, we built the first built the first built the first theories that still exist theories that still exist . . . Yes. Sorry. Yes. Sorry. Yes. Sorry. I said, better than this I said, better than this . . . Well, we both Well, we both Well, we both spent a lot of spent a lot of spent a lot of time implementing time implementing time implementing quantum quantum quantum cryptography. cryptography. cryptography. Of course. Of course. and with the Of course. Of course. and with the Of course. Of course. and with the very rudimentary very rudimentary very rudimentary quantum quantum quantum computers that have been computers that have been computers that have been created so created so created so far. And I think we're far. And I think we're far. And I think we're not upset that it's a not upset that it's a not upset that it's a long road that long road that long road that requires a lot of requires a lot of requires a lot of engineering work. engineering work. Jay, you meant that we not only that we not only came into contact with came into contact with came into contact with physical embodiments of physical embodiments of physical embodiments of our ideas, but our ideas, but our ideas, but actually built the actually built the actually built the first prototype, first prototype, that's right, the first one.

that's right, the first one. really. really. really. for cryptography for cryptography for cryptography about 5 about 5 about 5 years after years after years after the protocol was invented the protocol was invented the protocol was invented and exactly 10 years and exactly 10 years and exactly 10 years after the meeting in the after the meeting in the after the meeting in the ocean. ocean. ocean. Right. Right. But beyond that, But beyond that, Charlie and I are pure Charlie and I are pure Charlie and I are pure theorists. We're not theorists. We're not theorists. We're not experimental experimental experimental physicists, but I've been in touch physicists, but I've been in touch physicists, but I've been in touch with with with some experimental physicists some experimental physicists who are implementing these who are implementing these ideas on a large ideas on a large ideas on a large scale, starting scale, starting scale, starting with Nicolas in Geneva, with Nicolas in Geneva, with Nicolas in Geneva, who was the first who was the first who was the first to implement quantum to implement quantum to implement quantum cryptography over cryptography over cryptography over distances of tens of distances of tens of distances of tens of kilometers. Not just a kilometers. Not just a 10 km long spool of fiber optic where 10 km long spool of fiber optic where Alice and Bob Alice and Bob Alice and Bob are side by side. And the are side by side. And the are side by side. And the real physical real physical real physical distance was first distance was first distance was first done by Nicolas Gizan, done by Nicolas Gizan, done by Nicolas Gizan, who laid it under who laid it under who laid it under Lake Geneva Lake Geneva Lake Geneva to connect Geneva with to connect Geneva with to connect Geneva with Nyon, and later with Nyon, and later with Nyon, and later with Lausanne. And recently, Lausanne. And recently, extraordinary extraordinary practical work has been done in China to practical work has been done in China to practical work has been done in China to implement implement implement quantum quantum quantum cryptography on a cryptography on a cryptography on a large scale.

large scale. large scale. They have 10,000 kilometers of what They have 10,000 kilometers of what They have 10,000 kilometers of what they they they call a call a quantum quantum cryptography highway that is cryptography highway that is cryptography highway that is fully integrated fully integrated fully integrated with their space-based with their space-based with their space-based version. So they have version. So they have version. So they have satellites, and they satellites, and they satellites, and they can can can use use use quantum quantum quantum cryptography between the cryptography between the cryptography between the satellite and the satellite and the satellite and the backbone, and at backbone, and at backbone, and at this point in China, it's this point in China, it's this point in China, it's amazing how amazing how amazing how well equipped they are well equipped they are well equipped they are to implement our to implement our to implement our ideas in quantum ideas in quantum ideas in quantum cryptography. cryptography. From what I hear, there are From what I hear, there are already 5 million already 5 million quantum quantum cryptography users in China. cryptography users in China. cryptography users in China. You were just there, weren't you You were just there, weren't you You were just there, weren't you , sir? , sir? , sir? Yes. Yes. Yes. I was Yes. Yes. Yes. I was Yes. Yes. Yes. I was there just a few there just a few there just a few weeks ago. This is weeks ago. This is weeks ago. This is true. But I didn't true. But I didn't true. But I didn't visit their visit their visit their laboratories. I, I gave laboratories. I, I gave talks and talks and met and spent met and spent met and spent a few days with the a few days with the a few days with the person who person who person who is really the main, leading is really the main, leading is really the main, leading leader in leader in leader in experimental experimental experimental quantum quantum quantum cryptography, namely cryptography, namely cryptography, namely Pan Jianwei, Pan Jianwei, Pan Jianwei, known as, uh, um, known as, uh, um, sorry, I'm not here, it doesn't sorry, I'm not here, it doesn't matter, and, um, matter, and, um, matter, and, um, it was a very, very, it was a very, very, it was a very, very, very nice, very very nice, very very nice, very nice time with nice time with nice time with Jianwei. We Jianwei. We Jianwei. We discussed some of discussed some of discussed some of his latest his latest his latest achievements, but we achievements, but we achievements, but we did it in the desert, the did it in the desert, the did it in the desert, the Gobi Desert, Gobi Desert, Gobi Desert, riding riding riding camels. So, we couldn't camels. So, we couldn't camels. So, we couldn't , actually I , actually I , actually I couldn't see couldn't see couldn't see the equipment or anything the equipment or anything the equipment or anything . But even if I

. But even if I . But even if I had seen it, it wouldn't have been any had seen it, it wouldn't have been any had seen it, it wouldn't have been any different, because I wouldn't have different, because I wouldn't have different, because I wouldn't have understood it. Where I understood it. Where I understood it. Where I understand the theory, and I understand the theory, and I understand the theory, and I love talking to love talking to love talking to people, including people, including people, including experimentalists, experimentalists, experimentalists, about the theory. about the theory. So, for example, So, for example, satellites, satellites, space-scale quantum experiments, space-scale quantum experiments, they're 10 years old now, so they're 10 years old now, so they're 10 years old now, so these these these quantum quantum quantum key distribution experiments, which were key distribution experiments, which were key distribution experiments, which were BB-84 protocol with BB-84 protocol with BB-84 protocol with decoy state, decoy state, decoy state, were deployed were deployed were deployed over a thousand over a thousand over a thousand kilometers. kilometers. Oh, yes, that's Oh, yes, that's right, that's right, the right, that's right, the right, that's right, the first space first space first space experiment with a experiment with a experiment with a satellite, I think, satellite, I think, satellite, I think, was in 2017. was in 2017. M-hm. M-hm. So yes, he is 10 years old. So yes, he is 10 years old. So yes, he is 10 years old. Mm. But they have Mm. But they have improved tremendously since then improved tremendously since then . They built . They built . They built smaller and better, and smaller and better, and smaller and better, and smaller satellites, there were smaller satellites, there were smaller satellites, there were more of them, smaller more of them, smaller more of them, smaller receiving stations receiving stations receiving stations on Earth. In the on Earth. In the on Earth. In the initial version, it would initial version, it would initial version, it would have taken you have taken you have taken you several months to several months to several months to build a build a build a receiving station.

receiving station. receiving station. Now they have one in the Now they have one in the Now they have one in the truck and truck and truck and can deploy it can deploy it can deploy it in a matter of hours. in a matter of hours. in a matter of hours. They can bring They can bring They can bring it anywhere and it anywhere and it anywhere and deploy it in a matter of deploy it in a matter of deploy it in a matter of hours. This is a huge hours. This is a huge hours. This is a huge advance in this field, advance in this field, advance in this field, as is the huge as is the huge as is the huge advance in creating a advance in creating a advance in creating a quantum quantum quantum computer, which we have computer, which we have computer, which we have n't talked about yet. n't talked about yet. So quantum So quantum computers are really computers are really computers are really exciting, but they're also something that's exciting, but they're also something that's seen seen a lot of a lot of a lot of technological technological technological progress in the last progress in the last progress in the last few years. I've heard few years. I've heard few years. I've heard people, I think, I would people, I think, I would people, I think, I would say that regular say that regular say that regular software engineers software engineers , the people I , the people I , the people I talk to every day, don't talk to every day, don't talk to every day, don't think about think about think about post-quantum post-quantum post-quantum cryptography. But there is a cryptography. But there is a growing group of people who have a growing group of people who have a deep concern deep concern that this is what is that this is what is that this is what is going to happen, and it is going to happen, and it is going to happen, and it is going to happen very going to happen very going to happen very quickly. I wonder quickly. I wonder quickly. I wonder where, where should I be, where should I be where, where should I be, where should I be , where should my , where should my , where should my feelings be about feelings be about feelings be about post-quantum post-quantum post-quantum cryptography: somewhere cryptography: somewhere cryptography: somewhere between panic and between panic and between panic and enthusiasm, or enthusiasm, or enthusiasm, or panic, uh, complete panic, uh, complete panic, uh, complete panic, but, um, you panic, but, um, you panic, but, um, you say "post-quantum say "post-quantum say "post-quantum cryptography"—maybe cryptography"—maybe you don't know, you don't know, you don't know, or maybe you do know, or maybe you do know, or maybe you do know, what the difference is between what the difference is between what the difference is between post-quantum post-quantum post-quantum cryptography and cryptography and cryptography and quantum quantum quantum cryptography.

cryptography. cryptography. That's a great observation. That's a great observation. That's a great observation. These are completely different things. These are completely different things. These are completely different things. Quantum Quantum Quantum cryptography is something cryptography is something cryptography is something I invented in 1984, I invented in 1984, I invented in 1984, actually '83, where actually '83, where actually '83, where we we we use use use the laws of physics to the laws of physics to the laws of physics to transmit, to transmit, to transmit, to establish a establish a establish a secret key secret key secret key that is, uh, unbreakable that is, uh, unbreakable that is, uh, unbreakable according to the laws according to the laws according to the laws of physics, if the apparatus of physics, if the apparatus of physics, if the apparatus is built correctly is built correctly , which is not the most complicated , which is not the most complicated , which is not the most complicated thing. Whereas what's thing. Whereas what's thing. Whereas what's known as known as known as post-quantum post-quantum post-quantum cryptography is cryptography is cryptography is an attempt to, uh, an attempt to, uh, an attempt to, uh, use purely use purely use purely classical methods to classical methods to classical methods to achieve the same achieve the same achieve the same goals as RSA, Diffie- goals as RSA, Diffie- Gellman, and the current Gellman, and the current Gellman, and the current cryptographic cryptographic cryptographic infrastructure, which will infrastructure, which will infrastructure, which will completely collapse completely collapse when a when a when a quantum computer arrives. quantum computer arrives. So people are trying So people are trying hard to find different hard to find different hard to find different ways to achieve the ways to achieve the ways to achieve the same advantages with purely same advantages with purely same advantages with purely classical methods, classical methods, classical methods, but ones that would be but ones that would be but ones that would be unbreakable for unbreakable for unbreakable for quantum quantum quantum computers. Because computers. Because computers. Because we know that the current we know that the current we know that the current infrastructure is infrastructure is infrastructure is vulnerable. The problem is vulnerable. The problem is vulnerable. The problem is that post-quantum that post-quantum that post-quantum cryptography cryptography cryptography is trying to create is trying to create is trying to create something, to develop something, something, to develop something, something, to develop something, that we that we that we have absolutely no have absolutely no have absolutely no idea how to even idea how to even idea how to even begin to think about begin to think about begin to think about how to prove that it's how to prove that it's how to prove that it's secure. And so all secure. And so all secure. And so all this post-quantum this post-quantum this post-quantum cryptography cryptography cryptography can by definition can by definition can by definition be broken given be broken given unlimited unlimited computing computing computing power, whereas power, whereas power, whereas quantum quantum quantum cryptography cannot.

cryptography cannot. cryptography cannot. Moreover, post-quantum Moreover, post-quantum Moreover, post-quantum cryptography cryptography cryptography is based on faith. is based on faith. It's really wishful thinking that what they're that what they're inventing inventing inventing will actually be unbreakable by a will actually be unbreakable by a will actually be unbreakable by a quantum quantum quantum computer. It may computer. It may computer. It may turn out that it turn out that it turn out that it will not only be will not only be will not only be vulnerable to attack by a vulnerable to attack by a vulnerable to attack by a quantum quantum quantum computer, it may computer, it may computer, it may even fall before a even fall before a even fall before a classical classical classical computer. Because what is computer. Because what is being used in being used in post-quantum post-quantum post-quantum cryptography are cryptography are cryptography are tasks that are somewhat tasks that are somewhat tasks that are somewhat new, that have new, that have new, that have n't really been studied n't really been studied n't really been studied for centuries. RSA for centuries. RSA for centuries. RSA was based on was based on was based on factorization, which was a factorization, which was a factorization, which was a very old very old very old problem, but there were problem, but there were problem, but there were good reasons to good reasons to good reasons to believe that believe that believe that factorization was factorization was factorization was hard; and the big, hard; and the big, hard; and the big, big surprise is that big surprise is that big surprise is that quantum computers quantum computers quantum computers can break it, can break it, can break it, whereas the post-quantum whereas the post-quantum whereas the post-quantum cryptography that's cryptography that's cryptography that's being developed... There's being developed... There's being developed... There's absolutely no absolutely no absolutely no reason to believe that reason to believe that reason to believe that any of this any of this any of this offers any offers any offers any security. So, security. So, security. So, the answer is yes. the answer is yes. the answer is yes. So I would say, not So I would say, not So I would say, not exactly "no exactly "no exactly "no reason." reason." reason." Really? Really? Really? Good. Good. Good. Because they're looking for Because they're looking for Because they're looking for things that look things that look things that look different enough different enough different enough from factorization that from factorization that from factorization that if, for example, if, for example, uh, as many uh, as many uh, as many suspect, uh, suspect, uh, suspect, uh, one-sided functions one-sided functions one-sided functions still exist... uh, and still exist... uh, and still exist... uh, and that P is not equal to NP, that that P is not equal to NP, that that P is not equal to NP, that could also happen.

could also happen. could also happen. We don't know. I We don't know. I We don't know. I mean, all classical mean, all classical mean, all classical cryptography, except for cryptography, except for cryptography, except for one-time one-time one-time padlock and padlock and padlock and quantum quantum quantum cryptography, is cryptography, is cryptography, is provably insecure provably insecure . . Yes. Yes. But it can be But it can be But it can be practically safe practically safe practically safe if certain difficult if certain difficult if certain difficult tasks are really tasks are really tasks are really difficult. Previously, difficult. Previously, factorization was thought to be a factorization was thought to be a difficult task, but difficult task, but this is no longer the this is no longer the case for a quantum computer. So, "quantum" case for a quantum computer. So, "quantum" case for a quantum computer. So, "quantum" in this phrase, in what in this phrase, in what in this phrase, in what might be called the might be called the might be called the marketing marketing marketing term " term " post-quantum post-quantum post-quantum cryptography," cryptography," cryptography," means cryptography means cryptography means cryptography after the advent of after the advent of after the advent of quantum quantum quantum computers. The reason computers. The reason computers. The reason true true true quantum quantum quantum cryptography isn't a cryptography isn't a cryptography isn't a complete solution is complete solution is that many of the that many of the useful things useful things useful things you can do with you can do with you can do with information information information infrastructure, infrastructure, like digital signatures and like digital signatures and like digital signatures and especially especially public-key cryptography, where public-key cryptography, where people who don't people who don't people who don't know each other at all know each other at all know each other at all can verify can verify can verify who they're who they're who they're communicating with, are communicating with, are communicating with, are difficult. This is harder difficult. This is harder difficult. This is harder to implement to implement to implement with quantum with quantum with quantum cryptography with cryptography with cryptography with absolute security.

absolute security. I understand. I understand. Quantum Quantum Quantum cryptography solves cryptography solves cryptography solves the problem of secure the problem of secure the problem of secure communication. communication. Yes. But financial Yes. But financial connectivity doesn't solve connectivity doesn't solve connectivity doesn't solve many other many other many other problems that problems that problems that post-quantum post-quantum post-quantum cryptography has a cryptography has a cryptography has a chance to solve, although chance to solve, although chance to solve, although we can't we can't we can't prove it. prove it. prove it. But let's get back to But let's get back to But let's get back to the question of whether we should the question of whether we should the question of whether we should panic. The main panic. The main panic. The main reason for the panic is reason for the panic is not what I just not what I just not what I just said. Everything is much, said. Everything is much, said. Everything is much, much worse. By much worse. By much worse. By the way, when you the way, when you the way, when you asked if we should asked if we should asked if we should panic, I should have panic, I should have panic, I should have picked up on that and picked up on that and picked up on that and said, "What a good said, "What a good said, "What a good question." question." question." That would make me That would make me That would make me feel better at feel better at feel better at this moment. this moment. this moment. Sorry I didn't say Sorry I didn't say Sorry I didn't say it right away, but it's true. it right away, but it's true. So the reason we So the reason we should panic, the should panic, the should panic, the main reason, is the main reason, is the main reason, is the so-called " so-called " collect now, collect now, collect now, decrypt later" paradigm, in decrypt later" paradigm, in decrypt later" paradigm, in which there is nothing which there is nothing which there is nothing stopping an adversary stopping an adversary stopping an adversary from intercepting all from intercepting all from intercepting all encrypted encrypted encrypted messages on messages on messages on the Internet, just the Internet, just the Internet, just copying them, copying them, copying them, storing them, and keeping storing them, and keeping storing them, and keeping them. So all this them. So all this them. So all this encrypted encrypted encrypted information may information may information may already already already be stored somewhere and is be stored somewhere and is be stored somewhere and is likely in likely in likely in the hands of potential the hands of potential the hands of potential adversaries who adversaries who adversaries who cannot decrypt it yet cannot decrypt it yet cannot decrypt it yet because they do because they do because they do not yet know how to break not yet know how to break not yet know how to break RSA. But when a quantum RSA. But when a quantum RSA. But when a quantum computer becomes computer becomes computer becomes available to them, they available to them, they available to them, they will be able to get all will be able to get all will be able to get all this out of storage and this out of storage and this out of storage and decrypt everything decrypt everything decrypt everything retroactively. In other retroactively. In other retroactively. In other words, since RSA words, since RSA words, since RSA and DVM were virtually and DVM were virtually and DVM were virtually the only the only the only cryptographic cryptographic cryptographic tools in

tools in tools in use since the use since the padlock appeared in your browser to make you padlock appeared in your browser to make you believe in security, believe in security, almost every almost every message since then for message since then for dozens and dozens of dozens and dozens of years has been years has been years has been encrypted encrypted encrypted using RSA or using RSA or using RSA or Diffie-Hellman. Both of Diffie-Hellman. Both of Diffie-Hellman. Both of these methods are broken these methods are broken these methods are broken by a by a by a quantum quantum quantum computer. In other computer. In other computer. In other words, once a words, once a words, once a quantum computer quantum computer quantum computer becomes available, everything becomes available, everything becomes available, everything that has circulated on the that has circulated on the that has circulated on the internet will become an internet will become an internet will become an open book with open book with open book with hindsight. And what's hindsight. And what's hindsight. And what's worse, you can't do anything about worse, you can't do anything about worse, you can't do anything about it it it because this encrypted because this encrypted because this encrypted information is already in information is already in information is already in the hands of the adversary. the hands of the adversary. the hands of the adversary. You can't You can't You can't take it away from them. You can't take it away from them. You can't take it away from them. You can't stop stop stop them from decrypting it them from decrypting it them from decrypting it retroactively. When retroactively. When retroactively. When you have a you have a you have a quantum computer, there is quantum computer, there is quantum computer, there is absolutely no way you absolutely no way you absolutely no way you can can can save the past. All we save the past. All we can can can hope for is the hope for is the hope for is the future, future, future, using different using different using different methods: be it methods: be it methods: be it quantum or quantum or quantum or post-quantum post-quantum post-quantum cryptography. And in the cryptography. And in the cryptography. And in the case of case of case of post-quantum post-quantum post-quantum cryptography, you'll cryptography, you'll cryptography, you'll also have to also have to also have to believe. But believe. But believe. But quantum quantum quantum cryptography also cryptography also cryptography also requires faith. requires faith.

Quantum Quantum cryptography cryptography cryptography is proven secure, is proven secure, is proven secure, absolutely secure absolutely secure absolutely secure against an adversary with against an adversary with against an adversary with unlimited unlimited unlimited computing computing computing power and power and power and technology. But technology. But technology. But it is proven it is proven it is proven safe under two conditions safe under two conditions . The first is that quantum . The first is that quantum . The first is that quantum theory is correct, but theory is correct, but theory is correct, but we don't know it. And we don't know it. And we don't know it. And the second is that it is the second is that it is the second is that it is implemented implemented implemented correctly, which is difficult correctly, which is difficult correctly, which is difficult to do. So, nothing to do. So, nothing to do. So, nothing is perfect. To is perfect. To is perfect. To rephrase, to rephrase, to rephrase, to make sure I make sure I make sure I understand correctly: understand correctly: understand correctly: if post-quantum if post-quantum if post-quantum cryptography as a cryptography as a cryptography as a software protection software protection software protection will secure will secure will secure modern classical modern classical modern classical communications from communications from communications from future quantum future quantum future quantum computers, computers, computers, while acknowledging the significant while acknowledging the significant while acknowledging the significant period when we period when we period when we did not. did not. No-no-no, No-no-no, post-quantum post-quantum post-quantum cryptography if we cryptography if we cryptography if we move from the current move from the current move from the current infrastructure to infrastructure to infrastructure to post-quantum solutions. post-quantum solutions. Ugh. today—and that's Ugh. today—and that's going to take years—but if going to take years—but if going to take years—but if we were to switch today, we were to switch today, we were to switch today, it would in no way it would in no way it would in no way ensure ensure ensure security in the security in the security in the future, and that's future, and that's future, and that's my my my question, there's no question, there's no question, there's no guarantee that guarantee that guarantee that anything that anything that anything that 's encrypted 's encrypted 's encrypted between the time we between the time we switch to switch to post-quantum post-quantum post-quantum cryptography and cryptography and cryptography and later, when later, when later, when someone might someone might someone might find a way to find a way to find a way to break it, could all break it, could all break it, could all be broken be broken be broken retroactively in the retroactively in the retroactively in the same "store same "store same "store now, decrypt now, decrypt now, decrypt later" paradigm. In fact, the later" paradigm. In fact, the later" paradigm. In fact, the main advantage of main advantage of main advantage of quantum quantum quantum cryptography, in my cryptography, in my cryptography, in my opinion, is not that opinion, is not that opinion, is not that it is proven to be it is proven to be it is proven to be secure, because it is not secure, because it is not if it is if it is if it is implemented implemented implemented incorrectly. The main incorrectly. The main incorrectly. The main advantage of quantum

advantage of quantum advantage of quantum cryptography is cryptography is cryptography is that it is not susceptible to the that it is not susceptible to the that it is not susceptible to the "store now, "store now, "store now, decrypt later" attack. decrypt later" attack. If an attacker If an attacker finds a way finds a way finds a way to exploit a to exploit a to exploit a weakness in the weakness in the weakness in the implementation that implementation that implementation that allows the key to be obtained allows the key to be obtained allows the key to be obtained without detection—and without detection—and without detection—and this cannot be this cannot be this cannot be ruled out if there are ruled out if there are ruled out if there are flaws in the flaws in the flaws in the implementation—if he implementation—if he implementation—if he finds such a finds such a finds such a way, he must way, he must way, he must apply it apply it apply it during data transmission. during data transmission. After that, After that, the attacker has nothing left to the attacker has nothing left to work with. So the real thing about So the real thing about quantum quantum quantum cryptography that we cryptography that we cryptography that we can be proud of, and can be proud of, and can be proud of, and I quote Norbert I quote Norbert I quote Norbert Lutkenhaus from Lutkenhaus from Lutkenhaus from Waterloo, is when you Waterloo, is when you Waterloo, is when you use use use quantum quantum quantum cryptography, and I cryptography, and I cryptography, and I quote Lutkenhaus, " quote Lutkenhaus, " the key will remain the key will remain the key will remain as secure as secure as secure forever as it forever as it forever as it was immediately after was immediately after was immediately after transmission." Oh, I understand.

transmission." Oh, I understand. transmission." Oh, I understand. Of course. Of course. I really think the I really think the main advantage of main advantage of main advantage of quantum quantum quantum cryptography is that cryptography is that cryptography is that attackers have no attackers have no attackers have no way way way to store data for to store data for to store data for later later later decryption. If, decryption. If, decryption. If, if in 10 years if in 10 years if in 10 years they find a way, they find a way, they find a way, find, oh, was there a find, oh, was there a find, oh, was there a weakness in the weakness in the weakness in the implementation of what implementation of what implementation of what these people these people these people were using 10 were using 10 were using 10 years ago. Well, it's too years ago. Well, it's too years ago. Well, it's too late. This is late. This is late. This is useless. useless. Interesting. When you Interesting. When you said that, it occurred to me said that, it occurred to me said that, it occurred to me that the universe that the universe that the universe created a disposable created a disposable created a disposable notebook for us, and it notebook for us, and it notebook for us, and it will be will be will be realized someday. I, I realized someday. I, I realized someday. I, I saw you saw you saw you moving there, Charles. Did moving there, Charles. Did moving there, Charles. Did you want to add something you want to add something ? ? ? Oh, well, actually Oh, well, actually Oh, well, actually most of No, no, I don't most of No, no, I don't most of No, no, I don't think I wanted to think I wanted to think I wanted to add anything. I was going to add anything. I was going to add anything. I was going to make a somewhat make a somewhat make a somewhat humorous humorous humorous remark. So, remark. So, remark. So, speaking of the " speaking of the " panic now, panic now, panic now, decrypt later" approach, decrypt later" approach, what can we do what can we do about the insecurity of about the insecurity of about the insecurity of the materials that have already the materials that have already the materials that have already been collected? Of course, been collected? Of course, been collected? Of course, this can be used this can be used this can be used if some of our if some of our if some of our communications communications communications are of are of are of diplomatic or diplomatic or diplomatic or military interest.

military interest. They can be They can be used for used for purposes of national purposes of national competition, security, competition, security, competition, security, etc., but they can also be etc., but they can also be used for used for blackmail, for example blackmail, for example blackmail, for example if you ever if you ever if you ever wrote something wrote something wrote something embarrassing in an embarrassing in an embarrassing in an email. And email. And email. And we cannot we cannot we cannot effectively destroy this effectively destroy this effectively destroy this information. But what we information. But what we information. But what we could do is could do is publish publish numerous additional numerous additional numerous additional copies of it so that the price copies of it so that the price that that that the blackmailers will set will fall the blackmailers will set will fall the blackmailers will set will fall due to due to due to oversupply, and you won't oversupply, and you won't oversupply, and you won't have to pay have to pay have to pay so much to keep them so much to keep them so much to keep them quiet, no quiet, no quiet, no blackmailer will be able to blackmailer will be able to threaten you so much. So you threaten you so much. So you say: you know say: you know say: you know what, it's going to be what, it's going to be what, it's going to be published anyway. Well published anyway. Well , you know, make my , you know, make my , you know, make my day, instead of "okay, day, instead of "okay, day, instead of "okay, here's your money." here's your money."

There will be a lot of very There will be a lot of very interesting ethical and interesting ethical and interesting ethical and societal questions societal questions societal questions that will be that will be that will be explored as all of explored as all of explored as all of this happens. I this happens. I this happens. I wonder when we wonder when we wonder when we say that this is say that this is say that this is relevant and that it is relevant and that it is relevant and that it is coming soon. I've coming soon. I've coming soon. I've had a feeling for a long time that had a feeling for a long time that had a feeling for a long time that everything would be "soon." This is everything would be "soon." This is everything would be "soon." This is only five only five only five years later. It's always years later. It's always years later. It's always five years later. So five years later. So five years later. So just n plus 5. Do just n plus 5. Do just n plus 5. Do we have a sense of we have a sense of we have a sense of how inevitable how inevitable how inevitable this is going to happen, or is this this is going to happen, or is this this is going to happen, or is this one of those things where one of those things where one of those things where we overestimate the time we overestimate the time we overestimate the time it's going to happen and it's going to happen and it's going to happen and underestimate the impact? underestimate the impact? You're talking about You're talking about having a quantum having a quantum having a quantum computer computer computer powerful enough to powerful enough to powerful enough to break cryptography break cryptography and impact my and impact my life and the lives of people life and the lives of people life and the lives of people who don't understand who don't understand who don't understand such things but such things but such things but feel their feel their feel their impact. impact. impact. Well, it must be Well, it must be Well, it must be affecting your affecting your affecting your life already. Okay, life already. Okay, life already. Okay, because of what I explained because of what I explained , even if not, first of all , even if not, first of all , we don't know; , we don't know; , we don't know; maybe there's maybe there's maybe there's already a already a already a full-scale full-scale full-scale quantum computer running somewhere in the basement, quantum computer running somewhere in the basement, quantum computer running somewhere in the basement, uh, so we don't uh, so we don't uh, so we don't know. We have no know. We have no know. We have no way of knowing that way of knowing that way of knowing that this is not the case. But as I this is not the case. But as I this is not the case. But as I just explained, uh, it's just explained, uh, it's just explained, uh, it's not only supposed to not only supposed to not only supposed to affect your affect your affect your life already, because you have to life already, because you have to life already, because you have to worry about what's worry about what's worry about what's going to happen, uh, going to happen, uh, going to happen, uh, even retroactively, even retroactively, even retroactively, so no one should so no one should so no one should just sit back and just sit back and just sit back and relax and relax and relax and say, "Well, I'll say, "Well, I'll say, "Well, I'll worry when worry when worry when it happens," because it happens," because it happens," because then it's too then it's too then it's too late. That would be like late. That would be like late. That would be like not caring about not caring about not caring about climate change and climate change and climate change and saying, "Oh, we'll start saying, "Oh, we'll start saying, "Oh, we'll start worrying when worrying when worrying when the Earth is destroyed."

the Earth is destroyed." the Earth is destroyed." True. And, of course, True. And, of course, True. And, of course, society would never society would never society would never do that. do that. do that. No. Of course. No. No. No. Of course. No. No. No. Of course. No. No. No. God forbid. No. No. God forbid. No. Ahem. Wow. So, Ahem. Wow. So, given that the time to given that the time to given that the time to panic has come, how panic has come, how panic has come, how can you can you can you use this use this use this information in life and information in life and information in life and make the right make the right make the right choices and decisions, uh, choices and decisions, uh, choices and decisions, uh, so as not to so as not to so as not to get burned later? What are these get burned later? What are these get burned later? What are these things? What is the things? What is the things? What is the equivalent of " equivalent of " reduce, reduce, reduce, reuse reuse reuse , recycle , recycle " when you think about " when you think about " when you think about computer science in this computer science in this computer science in this way? way? Is that all? I don't have any I don't have any specific advice specific advice specific advice other than to simply not other than to simply not other than to simply not say things that say things that say things that would embarrass you would embarrass you would embarrass you if they became if they became if they became known. known. known. Always good advice. Always good advice. Always good advice. Always good advice. Always good advice. Always good advice. Truly timeless advice. Truly timeless advice. Truly timeless advice. Yes. Yes. Well, other than Yes. Yes. Well, other than Yes. Yes. Well, other than that, it's, um, uh, don't that, it's, um, uh, don't that, it's, um, uh, don't blindly trust the blindly trust the blindly trust the current current current infrastructure. Uh, infrastructure. Uh, infrastructure. Uh, remember that anything remember that anything remember that anything you say on the you say on the you say on the internet could become internet could become internet could become known in the known in the known in the future, when future, when future, when exactly—it’s unclear, exactly—it’s unclear, exactly—it’s unclear, but, um, keep that in mind but, um, keep that in mind but, um, keep that in mind , and so yeah, don’t , and so yeah, don’t , and so yeah, don’t say anything you say anything you say anything you might regret might regret might regret later. Or buy later. Or buy later. Or buy yourself some quantum yourself some quantum yourself some quantum cryptography cryptography cryptography equipment to equipment to equipment to communicate with your communicate with your communicate with your friends.

friends. friends. Yes. Which I actually have in my Yes. Which I actually have in my Yes. Which I actually have in my basement. I forgot to basement. I forgot to basement. I forgot to tell you. tell you. tell you. Also about when Also about when Also about when we will have a sufficiently we will have a sufficiently we will have a sufficiently powerful quantum powerful quantum powerful quantum computer, if we computer, if we computer, if we don't have one yet. No, I won't don't have one yet. No, I won't don't have one yet. No, I won't tell you what in 5 tell you what in 5 tell you what in 5 years. But what I can years. But what I can years. But what I can say is that the say is that the say is that the last few last few last few years have seen years have seen years have seen incredibly rapid incredibly rapid incredibly rapid technological technological technological progress. So, and this is progress. So, and this is progress. So, and this is very, very clear, and no very, very clear, and no very, very clear, and no one can just one can just one can just close their eyes and close their eyes and close their eyes and say, "Oh, this will say, "Oh, this will say, "Oh, this will never happen." never happen." never happen." 15 years ago, it was 15 years ago, it was 15 years ago, it was acceptable for someone to acceptable for someone to acceptable for someone to say nothing. say nothing. say nothing. There are a few other people who There are a few other people who There are a few other people who say that, but they are say that, but they are say that, but they are wrong. wrong. wrong. But, you know, in the But, you know, in the But, you know, in the last year or two, last year or two, last year or two, maybe three, it seems like maybe three, it seems like we're starting to move we're starting to move we're starting to move up the up the hockey stick curve in hockey stick curve in hockey stick curve in this area. this area. this area. This is true. This is true. This is true. This is true. This is true. This is true. This is true. that there is indeed This is true. that there is indeed extraordinary progress , technological , technological , technological progress that makes progress that makes progress that makes us believe that this us believe that this us believe that this will happen soon. will happen soon. will happen soon. But how soon— But how soon— I don't want to try to I don't want to try to I don't want to try to predict. predict. predict. Yes. Well, thank you Yes. Well, thank you Yes. Well, thank you both for your time and for both for your time and for both for your time and for your contributions to this your contributions to this your contributions to this industry. We really industry. We really industry. We really appreciate you and thank you appreciate you and thank you appreciate you and thank you for taking the time for taking the time for taking the time to chat with to chat with to chat with me on ACM ByteCast.

me on ACM ByteCast. me on ACM ByteCast. Thank you both very much. Well, would Thank you both very much. Well, would Thank you both very much. Well, would you like to hear you like to hear you like to hear about, excuse the expression, about, excuse the expression, about, excuse the expression, artificial intelligence? artificial intelligence? If you want, I know If you want, I know some of us some of us some of us are interested in this are interested in this are interested in this topic. I think I would be topic. I think I would be topic. I think I would be interested, interested, interested, Charles H. Bennett, Charles H. Bennett, Charles H. Bennett, to hear your thoughts on to hear your thoughts on to hear your thoughts on AI in the context of AI in the context of AI in the context of whether it will take my whether it will take my whether it will take my job. But I want to job. But I want to job. But I want to get some get some get some advice or facts that I advice or facts that I advice or facts that I can take with me into my can take with me into my can take with me into my daily life and daily life and daily life and understand how to understand how to understand how to deal with it. But deal with it. But deal with it. But if you have something to if you have something to if you have something to share, of course, share, of course, share, of course, please do. Well, I please do. Well, I please do. Well, I think the reason why think the reason why think the reason why it's more painful than when it's more painful than when it's more painful than when machines started machines started machines started doing other doing other doing other routine things, uh, is because routine things, uh, is because people consider scientific research scientific research and the work that and the work that mathematicians or theoretical physicists do, for example, trying trying to prove something, to be the highest, to prove something, to be the highest, to prove something, to be the highest, most most intellectually intellectually complex human complex human complex human activities.

activities. activities. So if they, So if they, if computers if computers can do it can do it can do it much better, then what is much better, then what is much better, then what is left for left for left for me? Mm. me? Mm. And the example I And the example I would like to give here would like to give here would like to give here comes from comes from comes from computer science, computer science, okay, so I'll take a okay, so I'll take a part of theoretical computer part of theoretical computer part of theoretical computer science that is science that is science that is known to many known to many known to many people at the ACM, but people at the ACM, but people at the ACM, but maybe not everyone, and that's something maybe not everyone, and that's something maybe not everyone, and that's something called called interactive interactive proof theory. And that proof theory. And that proof theory. And that goes for the question goes for the question goes for the question of questions you can of questions you can of questions you can usually ask. usually ask.

Complexity classes Complexity classes such as P, NP, and P-space such as P, NP, and P-space such as P, NP, and P-space refer to refer to refer to how much of a particular how much of a particular how much of a particular resource, such as time or resource, such as time or resource, such as time or memory, must be memory, must be memory, must be used to used to used to solve a problem. solve a problem. But this is a But this is a problem-solving situation in problem-solving situation in problem-solving situation in which there are two participants which there are two participants which there are two participants or two types of or two types of or two types of participants. There is an honest participants. There is an honest participants. There is an honest but but but limited participant limited participant limited participant called called called Arthur, and an Arthur, and an Arthur, and an infinitely wise infinitely wise infinitely wise but utterly untrustworthy but utterly untrustworthy participant called participant called Merlin, like Merlin Merlin, like Merlin the Wizard. The idea the Wizard. The idea the Wizard. The idea is whether there is a is whether there is a is whether there is a way for Merlin way for Merlin way for Merlin to convince Arthur of to convince Arthur of to convince Arthur of the truth of something the truth of something the truth of something that Arthur would not be able to that Arthur would not be able to that Arthur would not be able to verify on verify on verify on his own by performing his own by performing his own by performing all the necessary tests, all the necessary tests, all the necessary tests, as it would as it would as it would take too take too take too much of his time. So, well, much of his time. So, well, much of his time. So, well, the theory of interactive the theory of interactive the theory of interactive proofs has several proofs has several proofs has several results, but one results, but one results, but one of the most famous is of the most famous is of the most famous is that that that if Merlin and Arthur if Merlin and Arthur if Merlin and Arthur interact in interact in interact in just polynomial just polynomial just polynomial time, time, then Merlin can then Merlin can convince Arthur of convince Arthur of convince Arthur of the truth or the truth or the truth or falsity of any falsity of any falsity of any question that Arthur question that Arthur question that Arthur could could could solve on his own in just

solve on his own in just solve on his own in just polynomial polynomial polynomial time. In other time. In other time. In other words, it seems to words, it seems to words, it seems to encompass encompass encompass exponentially more exponentially more exponentially more difficult problems, difficult problems, difficult problems, including most of including most of including most of those of interest to those of interest to those of interest to mathematical physicists mathematical physicists . Of course, this is an . Of course, this is an . Of course, this is an unrealistic model unrealistic model , as it , as it , as it involves the character of involves the character of involves the character of Merlin, who supposedly Merlin, who supposedly Merlin, who supposedly knows everything, perhaps knows everything, perhaps knows everything, perhaps even the solution to the even the solution to the even the solution to the halting problem. But halting problem. But halting problem. But just the ability just the ability just the ability for Arthur for Arthur for Arthur to talk to him and to talk to him and to talk to him and ask adaptive ask adaptive ask adaptive questions, where if he questions, where if he questions, where if he lies, Arthur will expose lies, Arthur will expose lies, Arthur will expose him in him in him in polynomial time, polynomial time, polynomial time, gives this system gives this system gives this system much more much more much more power. And another power. And another power. And another recent result recent result recent result in this field, in this field, in this field, related to related to related to quantum quantum quantum computing, computing, computing, Mgm. or at least with Mgm. or at least with Mgm. or at least with quantum quantum quantum information processing like information processing like information processing like teleportation, is that teleportation, is that instead of one instead of one Merlin you have two, and Merlin you have two, and Merlin you have two, and they are quantum, and they are quantum, and they are quantum, and Arthur remains Arthur remains Arthur remains classical and classical and classical and bounded by bounded by bounded by polynomial time polynomial time , with the quantum , with the quantum , with the quantum Merlins being entangled Merlins being entangled Merlins being entangled but not allowed to but not allowed to but not allowed to communicate with communicate with communicate with each other. So Arthur can each other. So Arthur can each other. So Arthur can ask these two ask these two ask these two confused Merlins confused Merlins confused Merlins questions that will questions that will questions that will expose them if expose them if expose them if they try to they try to they try to lie. Well, especially lie. Well, especially lie. Well, especially because he asks because he asks because he asks them individual questions.

them individual questions. them individual questions. And their entanglement will And their entanglement will And their entanglement will help them help them help them cooperate in some cooperate in some cooperate in some way, but way, but way, but not well enough not well enough not well enough to fool Arthur. to fool Arthur. And the result, And the result, proven about proven about proven about six years ago, six years ago, six years ago, was that in was that in was that in this situation, such this situation, such this situation, such Merlins could Merlins could Merlins could convince Arthur to convince Arthur to convince Arthur to stop any stop any stop any Turing machine. In Turing machine. In other words, in other words, in any kind of any kind of any kind of computation computation computation whose duration you whose duration you whose duration you can't even can't even can't even predict. predict. For example, the For example, the simplest case simplest case is the unsolved is the unsolved is the unsolved mathematical conjecture mathematical conjecture known as known as known as Goldbach's conjecture, which Goldbach's conjecture, which Goldbach's conjecture, which states that every states that every states that every even number except even number except even number except two is the sum of two two is the sum of two two is the sum of two prime numbers. You prime numbers. You prime numbers. You could check this could check this could check this forever, but so far no forever, but so far no proof has been found, nor, proof has been found, nor, of course, an example of an of course, an example of an of course, an example of an even number that even number that even number that cannot be obtained by cannot be obtained by cannot be obtained by adding two adding two adding two prime numbers. Now, prime numbers. Now, prime numbers. Now, if in this scenario if in this scenario if in this scenario there is a negative there is a negative there is a negative answer to answer to answer to Goldbach's conjecture, in Goldbach's conjecture, in Goldbach's conjecture, in other words, if other words, if other words, if it is false, two it is false, two it is false, two quantum provers quantum provers quantum provers could prove it to could prove it to could prove it to Arthur in a very Arthur in a very Arthur in a very limited amount of time limited amount of time limited amount of time with a proof with a proof with a proof that Arthur could that Arthur could that Arthur could actually believe.

actually believe. Now, the subtle interesting thing about Now, the subtle interesting thing about this, this, this, or one of them, is that or one of them, is that let's say let's say Gold's conjecture is true, and Gold's conjecture is true, and Gold's conjecture is true, and in fact, if you in fact, if you in fact, if you were to look for a were to look for a were to look for a counterexample, you would counterexample, you would counterexample, you would never never never find one. We would say, find one. We would say, find one. We would say, well, these two quantum well, these two quantum well, these two quantum arguments, they're arguments, they're arguments, they're infinitely wise, infinitely wise, infinitely wise, so they already know the so they already know the so they already know the answer to this. Ca answer to this. Ca answer to this. Ca n't they just n't they just n't they just tell Arthur: yes, there is tell Arthur: yes, there is tell Arthur: yes, there is no answer? There no answer? There no answer? There is no counterexample is no counterexample is no counterexample to the hypothesis. No, because to the hypothesis. No, because to the hypothesis. No, because they can say, they can say, they can say, they can they can they can convince Arthur convince Arthur convince Arthur if the answer is that if the answer is that there is a counterexample, there is a counterexample, but they can't but they can't but they can't convince him that there is convince him that there is convince him that there is n't, because they n't, because they n't, because they know the answer to the know the answer to the know the answer to the halting problem, but halting problem, but halting problem, but they're unreliable. So, they're unreliable. So, they're unreliable. So, if they tell if they tell if they tell him the answer is no, him the answer is no, him the answer is no, it won't allow him it won't allow him it won't allow him to believe it's to believe it's to believe it's no. So it's a very subtle no. So it's a very subtle no. So it's a very subtle thing, but it thing, but it thing, but it says that, says that, says that, to continue the analogy to continue the analogy to continue the analogy further, in ordinary further, in ordinary further, in ordinary everyday life, everyday life, everyday life, if you think that if you think that if you think that your relationship with your relationship with your relationship with artificial intelligence is artificial intelligence is artificial intelligence is like like like Arthur's relationship with Merlin, you Arthur's relationship with Merlin, you Arthur's relationship with Merlin, you shouldn't trust what shouldn't trust what shouldn't trust what it says, but it says, but it says, but you should trust you should trust you should trust its ability to its ability to its ability to help you help you help you convince yourself of convince yourself of convince yourself of something that is true, something that is true, something that is true, because you just because you just because you just need to learn to need to learn to need to learn to ask it ask it ask it questions in the right questions in the right questions in the right way. And I think that's how way. And I think that's how way. And I think that's how we should we should we should approach approach approach artificial intelligence.

artificial intelligence. That is to say that we That is to say that we can't trust them can't trust them , but they can , but they can , but they can help us because we help us because we help us because we can figure out how to can figure out how to can figure out how to ask them questions ask them questions ask them questions where they either tell where they either tell where they either tell us the truth or we us the truth or we us the truth or we catch them in a catch them in a catch them in a lie. OK. And lie. OK. And lie. OK. And let me add that let me add that let me add that the invention of the invention of the invention of interactive interactive interactive proofs was proofs was proofs was awarded the awarded the awarded the Turing Award in 2012 to Turing Award in 2012 to Turing Award in 2012 to Silvio Micali and Silvio Micali and Silvio Micali and Shafi Goldwasser. Shafi Goldwasser. Yes. Yes. Although it Yes. Yes. Although it was also invented was also invented was also invented independently by László independently by László independently by László Babayi, who did not Babayi, who did not Babayi, who did not share the share the share the Turing Award in 2012. Turing Award in 2012. Turing Award in 2012. Well, now that's it. Well, now that's it. Well, now that's it. But because the But because the But because the Turing Award was also Turing Award was also Turing Award was also about cryptographic about cryptographic about cryptographic applications. applications. applications. Yes. Well then IP Yes. Well then IP Yes. Well then IP equals PSPACE was equals PSPACE was equals PSPACE was a little earlier than that, was a little earlier than that, was a little earlier than that, was n't it Shamir or n't it Shamir or n't it Shamir or someone else? someone else? Yes. So, in any case, this is a any case, this is a any case, this is a very hot topic in very hot topic in very hot topic in theory. theory. theory. It should have been so, It should have been so, It should have been so, no, IP equals PSPACE no, IP equals PSPACE no, IP equals PSPACE should have been later. It's should have been later. It's should have been later. It's not enough. not enough. not enough. Oh, yes. Yes. Oh, yes. Yes. Oh, yes. Yes. It was rediscovered. It was rediscovered. It was rediscovered. Yes. Yes. Yes. But I'm not sure in But I'm not sure in But I'm not sure in what order the what order the what order the Turing Award was given.

Turing Award was given. Turing Award was given. In any case, In any case, In any case, she received she received she received at least one at least one at least one Turing Award. Turing Award. Turing Award. Yes. Yes. And a newer job might And a newer job might get another one over get another one over get another one over time. time. time. Oh, yes, she should. Oh, yes, she should. Oh, yes, she should. Yes. Yes. Yes. She must. Yes. She must. Yes. She must. Yes. So I think that's an So I think that's an So I think that's an optimistic reason optimistic reason optimistic reason to say, look, to say, look, to say, look, machines are actually machines are actually machines are actually taking over the taking over the taking over the less important part of less important part of less important part of our work, and our our work, and our our work, and our job is to learn job is to learn job is to learn to be good. to be good. Arthur and don't let Arthur and don't let these these these machines fool you, even though machines fool you, even though machines fool you, even though they help us a lot they help us a lot they help us a lot . I . I don't know if any of don't know if any of you are into you are into you are into science fiction science fiction . Of course, in the field . Of course, in the field . Of course, in the field you work in, you have to you work in, you have to you work in, you have to think about such things. think about such things. think about such things. But when you But when you But when you told that told that told that story, I immediately story, I immediately story, I immediately remembered the remembered the remembered the Harry Mudd episode from Harry Mudd episode from Star Trek, when Star Trek, when Star Trek, when Captain Kirk says, " Captain Kirk says, " Everything Harry tells you Everything Harry tells you is a lie." No matter what is a lie." No matter what , everything he says is a , everything he says is a , everything he says is a lie. And then he lie. And then he lie. And then he says, "I'm lying," and then says, "I'm lying," and then says, "I'm lying," and then the android can't the android can't the android can't reconcile the statement reconcile the statement reconcile the statement that he's lying with the that he's lying with the that he's lying with the lie. So, he lie. So, he lie. So, he tells the truth, and then tells the truth, and then tells the truth, and then he explodes. So in he explodes. So in he explodes. So in that case, humans that case, humans that case, humans outsmarted outsmarted outsmarted AI by being AI by being AI by being smarter and smarter and smarter and exploiting the exploiting the exploiting the liar paradox.

liar paradox. liar paradox. That's right. Well, That's right. Well, That's right. Well, my granddaughter's version is this: how my granddaughter's version is this: how my granddaughter's version is this: how would would would Pinocchio react if you Pinocchio react if you Pinocchio react if you asked him if asked him if his nose was about to his nose was about to his nose was about to get longer? get longer? That's a good question. Well, thank you both for Well, thank you both for giving me giving me giving me so much time. You are very so much time. You are very so much time. You are very generous. I want to generous. I want to generous. I want to thank you both. thank you both. thank you both. Charles G. Bennett Charles G. Bennett Charles G. Bennett and Gilles Brassard. and Gilles Brassard. and Gilles Brassard. Oh, he probably Oh, he probably Oh, he probably has your initial in has your initial in has your initial in the middle too, right? Do the middle too, right? Do I have it? Do I have it? Do you have it? you have it? you have it? Oh, Oh, Oh, no. Of course. That no. Of course. That no. Of course. That I I put I I I I put I I I researched this for "G" I researched this for "G" because Charles and Bennett are because Charles and Bennett are very common names, very common names, very common names, and there are quite a few other and there are quite a few other and there are quite a few other scientists named Charles scientists named Charles scientists named Charles Bennett. Bennett. Bennett. No, I understand. I respect the No, I understand. I respect the No, I understand. I respect the initial in the middle, initial in the middle, initial in the middle, Charles G. Bennett. And Charles G. Bennett. And Charles G. Bennett. And we spoke with we spoke with we spoke with Charles G. Bennett Charles G. Bennett Charles G. Bennett and Gilles Brassard, and Gilles Brassard, and Gilles Brassard, winners of the winners of the winners of the Alan Turing Award, the Alan Turing Award, the Alan M.

Alan M. Turing Foundation Award, this is a nice Turing Foundation Award, this is a nice Turing Foundation Award, this is a nice touch, for touch, for touch, for fundamental fundamental fundamental contributions to quantum contributions to quantum contributions to quantum computing. Thank computing. Thank computing. Thank you both very much. you both very much. you both very much. Thank you, Scott. It was Thank you, Scott. It was Thank you, Scott. It was nice nice nice talking to you. talking to you. talking to you. Yes. See you later.