Episode 360 - Quantum Punks with Alex and Nicola

Transcript

[Music] Welcome to Zero Knowledge. I'm your host, Anna Rose. In this podcast, we will be exploring the latest in zero knowledge research and the decentralized web, as well as new paradigms that promise to change the way we interact and transact online. [Music] This week, GMO and I explore the aims of the crypto punk movement with co-creators Alex and Nicola. Alex is a long-standing builder in the crypto industry, most recently as a co-founder of Flashbots, and is now the program director of Arya, the UK's DARPA

equivalent, where he's currently focused on funding new cryptography based on natural laws. Nicola has been leading the cryptography R&D effort at Protocol Labs for the last eight years and also founded the syndicate Deep Crypto. In this episode, we discussed the Quantum Punks Manifesto, returning to the topic of quantum cryptography and looking at how this compares to other eras in more familiar cryptographic areas. It was very exciting to dig back into the quantum cryptography side of things. We get a chance to cover lots of applications for this stuff. So, yeah, hope you enjoy. We do reference an event that Nicola and Alex held in Paris back in March. We're going to try to dig up the links to these videos. We mentioned them a couple times throughout the

episode, so look for these in the show notes. Now, before we kick off, I just want to let you know that ZKS Summit 13 is happening on May 12th in Toronto. The event is coming up fast, and if you haven't yet bought your ticket, we do encourage you to do so. Also, we do have some student tickets still available. So, if you would like to apply for a student discount, you can do so over on our website, zksummit.com. Hope to see you there. Now, Tanya will share a little bit about this week's [Music] sponsor. You might already know the ZK jobs board, a place where teams can share open roles with our community, but when it comes to key hires, finding the right fit in our niche space can be difficult. That's where Missing Link

comes in. They're a talent team built for the web 3 era, helping projects across the ecosystem connect with the right candidates at the right time. They've worked with names you'll recognize. Ethereum Foundation, Matter Labs, Lido, Mina, Web3 Foundation, and many more, filling critical roles that drive these teams forward. Whether you're an established project looking to fill a senior leadership role or a startup searching for specialized talent to refine your product market fit, Missing Link can help. They've done it for some of the biggest teams in the space, helping them and now you find the right people fast. For more details, check out the show notes and visit their website at missing-link.io. So, thanks again,

Missing Link. And now, here's our [Music] episode. Today, GMO and I are here with Nicola and Alex, the co-authors of the Quantum Punks Manifesto. The Quantum Punk community explores the intersection between quantum and cryptography. And this is hopefully what we're going to get a chance to jump into today. So, welcome to the show, Alex and Nicola. Thank you for having us. Happy to be here. Thank you, everyone. Happy to be here. Hi, GMO. What's up? excited for another quantum episode.

Yeah, I know. It's great. I get uh dragged onto the physics stuff which uh is, you know, harking back to old memories. Yeah. So, just a few weeks ago, GMO and I did an episode with Yelina Vauovich uh where we did an intro to quantum engineering. I'll add the link to this in the show notes in case the listener would like to get some background. Today, I feel like the focus will be primarily on the overlap between what we covered in that episode and the cryptography space. We're going to be talking a little bit more about that intersection. When I think about quantum and cryptography, I feel like it might be good to just kind of define a few different ways that we hear those terms combined. One is like quantum will break cryptography. So, some classic

cryptography they don't think will stand up to quantum computers. There's also postquantum cryptography which is current cryptography classic which people think will be able to stand up to quantum computers won't be broken. But then there's this third category which is quantum cryptography and I feel like when it comes to the quantum punks this is the area you guys are most focused on. Am I right? Absolutely. Cool. Okay. So, but before we do jump in to this quantum cryptography, cryptography built for a quantum environment, I feel like it would be great to talk about your backgrounds and what led you to work on this. I feel like I know both of you originally from the ZK space actually or

I've seen you at events. You were both involved. Nicola, let's start with you. You were actually on the show long ago. We did an episode. I recorded it at Zecon Zero. It was like an event episode where I interviewed about 13 people and you were one of those interviews. At the time you were focused entirely on ZK. So what's been your history since that point? What got you into quantum? So what happened is uh back then it was the I would say the first few years of zero knowledge proofs. Yes. And uh I was working at protocols and I've worked at protocols for over eight years and I led the crypto uh the cryptography and protocol design R&D team there. We worked on making zillidge proofs more

and more practical. And uh in a way back in those days like a few years before I was a a PhD student at MIT and some of my professors told me well ZK is still academic material not going to work and uh it's insane what happened 10 years later and in a way when looking for um what is a what is today at that stage h we looked into quantum cryptography and to some extent when we talked to professor about quantum cryptography.

these professors tell us well this is academic material and in a way I relieve that experience and uh in a way we I don't know Alex and I built thick skin on people not believing in super early technologies and uh so I'm very excited actually when I hear that in quantum cryptography and did that get you started that kind of got you excited and you decided okay this is what I want to work on now this is more like an exploratory area for me I love this working on this moment of a technology where it's unclear if it can be practical but uh the more you dive deep into maybe there is some lowh hanging fruits and uh I'm actually very excited to to find either myself or to help

other people find that's why we wrote the manifesto to find more and more intersections between quantum and the cryptocurrency industry and quantum so that we could have uh new applications and maybe better hardware driven by these new applications. Nice. Alex, what about you? What's your background and what led you to work on this? Yeah, so I've been more around the cryptography sector. So before the quantum punk stuff, I was uh building building flash bots for a few years. There's some privacy element to what we were doing. Uh we came at it from this very practical perspective of okay, we need to add privacy to what we're doing. And we went more in the trusted hardware direction, but we still explored um all these other primitives. And before that

I was running these ZK meetups in in London and uh having fun doing that in like 2017 2018. And so yeah I've been around and super interested in in cryptography always thinking that cryptography is one of those things in the blockchain industry that it feels very tangible to me. And so when I whenever I have like a crisis for faith, you know, cryptography is one of it's it's the one of the kind of like stable point that I I kind of go back to and I'm like this has applications way beyond the the the industry that I'm in. And it's also just so so fascinating and it relies on something that I can understand which is like okay it's based on new maths or uh new new methods that are kind of like understandable. Um, and so Nico and I were meeting regularly uh

to catch up and hang out, share ideas. And he kind of told me, "Dude, like quantum is is booming. It's super exciting. And I'm hearing about this quantum cryptography stuff, but it feels a little bit like far, maybe is it too far? And should I focus on IO or should I focus on this instead? Like what what are the problems that I should really focus my next, you know, big adventure on?" And uh when he told me about quantum I was like dude this this is sick. This sounds like the most exciting thing. And also if even if you think it might be a little bit further away now you're not factoring in our own power to potentially accelerate it the same way what we've seen with the zero knowledge space. And so we kind of committed to okay let's explore it. And from there we

kind of started going to events looking really stupid and asking like very basic questions like quantum events or Yeah. Yeah. Yeah. Exactly. We went to one particular quantum event where it was full of quantum companies and we we just showed up you know we're like two little like hey we're from the crypto industry and so uh you know people were like confused what we were doing here nice and uh we were just asking basic questions and I think from that event specifically we came out of it both realizing okay there's a gap here they don't know that there's a whole ecosystem that is so hungry for new cryptographic primitives and that if you if you give them those tools they're like get so excited about the types of applications they build. On the other side, the crypto people don't seem to be aware that this exists. And when you

mention quantum, it's usually about postquantum secure uh systems. And so we just felt, okay, there's an intersection here. Not only a gap in communication, but also a gap in culture where the event we went to felt a little bit like corporates and traders, where the like misfits, you know, uh where are the people that are kind of like overselling their projects, which is like super common in crypto. Uh, and and you kind of need to some extent you need the dreamers, you know, you need the people that are like really thinking about the big picture. I was just thinking like the brainstormers or the idea people, it sounds like the the ones with the weirder ideas. Yeah, exactly. Missing the idea guys, missing the philosopher kings, whatever you want to call them. Um, and so and so from from there, we were back in the taxi at

the end of the day and we were like, dude, we have to we have to do something. We have to at least point out that this intersection exists. And from there we worked on okay let's write a manifesto. Uh that's like the most like you know uh culturally appropriate way for us to do this so that we really bring the values we think are important to bring in there. And so that's kind of how we went about. Cool. The the manifesto is actually it's actually quite lovely. I mean it's a short short document clearly outlines stuff. I I came in for what it's worth very skeptical because you know as usual like like sorry Alex I I I actually know you quite well. I was less skeptical because of that, but nevertheless, I was appreciate that somewhat skeptical uh and was like, "Oh, yeah." Like quantum,

you know, the the number of times I've heard quantum in like the years I before I studied it and then when I studied it and then afterwards has been, you know, hilarious. Uh but then I read the thing and I was like, "No, actually, this is this is quite quite reasonable." I mean, obviously still forward-looking for sure, but it's it's an easy thing to rally around. It's clean. It's clear. I was very impressed uh in the writing. Like I honestly like I say that about but very few quote unquote manifestos, you know, but like this was actually quite quite good. Uh so yeah, very excited to to dig into the the philosophy ideas notions constructions behind all the stuff.

Thank you for all the compliments. I'm glad you say that. I'm glad you say that because we actually spent an insane amount of time on this manifest. I can tell. We wrote it in 10 different versions and then I remember one day I said, "Alex, I think uh I'm sorry. I think maybe we need to write it from scratch and uh and that happened several times and I think Alex has been a meticulous author and editor of a lot of Yeah. Know I I feel that deeply because that's uh a lot of my papers often go through complete from scratch four or five rewrites and I can I can tell that that happened here because the ideas are very clean. They're nicely organized.

They say exactly the thing. Two sentences describe it. No more no less. Uh, and I I'll stop with the, you know, uh, if praise, but nevertheless, I Yeah, this is very cool. Maybe we should actually jump into what's in this manifesto. Do you guys want to share with us sort of the overarching ideas, what you're trying to cover? Let me just give you one some context. Uh like Alex said, there is a a big gap between the two communities and we wanted to find some applications that would make both communities excited and um in in some ways quantum cryptography it's not something new.

People have been studying theoretical u applications of quantum cryptography and not only for 10 year plus there are companies that build quantum key distribution systems but a lot of these systems have applications mostly in defense and in a way um it's like for secure communications between armies or banks I don't know but it's very cyber security oriented and if you think about the early stage of the internet the internet was some sort of defense communication technology totally and So, we kind of wanted to try our best to wake up people and say, "Hey, if the internet stayed at defense, we would not have social media, e-commerce, Tik Tok, and similar things." Yeah. I don't know

if we want any of those things. True. But yeah, true. I mean, like the world we know today would be different. Let's say that. Let's say that. But uh and what happened in cryptography in a way even cryptography started as defense and then we started thinking about what can we do for um the final users and so what what tool can we build so that the individual can feel more powerful and so this was what started the cyberpunk movement back in the 80s and so Alex and I spent some time thinking what if we could bring some cypher punk to the quantum industry. H and the more we looked into this, the more we realized that uh quantum cryptography is some

sort of cyber punk endame where there are things that you can do with quantum cryptography that you cannot do with classical cryptography. Mhm. And so not only we could use quantum cryptography to better secure existing systems from quantum computers, but we have a way to build new cryptography. And we're going to touch on that into the rest of the podcast. And new cryptography primitives have generated an incredible amount of value. In a way, encryption gave us uh private messaging. Signatures gave us HTTPS and the ability to do e-commerce online or communicate uh online. And

consensus gave us blockchains. We're yet to see what zero knowledge proofs are going to give to the to the mainstream users. But uh I wonder what can quantum cryptography give us that we cannot think about because you cannot just do it with classical cryptography. So that's how it that's how it started and that there are two main pieces in this manifesto which is uh quantum accelerationism and the other one is uh new applications of uh quantum cryptography for cypher punk applications. Cool. the cippher punk applications. It it's kind of repeating a little bit of what we said before which is saying hey if we have new cryptographic primitives by new I mean they enable new capabilities there are new applications we can build with it

and um the kind of product market fit for these new tools is probably cippher punk applications just because the in the cypher punk ideals we care about the most secure systems and we care about some of these guarantees a lot trustlessness or trust minimization is is is critical for some other applications it isn't And so on one side, it's to tell people from the privacy and cryptography industries, you guys should look over here. Um, this is probably the endgame for what you're for what you want to do. This is this these are the systems that will be the most secure. These are the systems that you might even they're secured by physics. Exactly. Secured by physics instead of computational assumptions. Um, you might not even need to rely on hardware anymore thanks to

some of some of the new primitives you have. Wow. And you have these kind of new world of primitives that emerge. And so the first one is new applications can be created with this. And the second kind of tenant of the manifesto is those new applications are going to garner funding and uh demand from users but also funding from investors like like on this call. Um and that that that creates a virtual cycle that we've seen and we're for us we're very familiar with it which is the space accelerates. researchers start working in industry, whole teams start being poached from academia to to startups to accelerate specific primitives on a specific metric that is incremental and so less interesting to academia but very interesting to to industry. Um and from

there what you get is an acceleration of quantum hardware more generally. And so the quantum acceleration is amida by having more demand for these primitives. You have more demand for the underlying infrastructure that enables them which creates this broader movement within quantum technologies not only uh quantum cryptography. And that has this kind of knock-on effects that can bring about the the general kind of um benefits of quantum technologies that go beyond just quantum cryptography. And so it is kind of saying a new growth vector that can come into the quantum technology space that is not the quantum computing paradigm or narrative nor is it the quantum sensing narrative but the cypher

punk applications of quantum networks. Um, and so the first point in new applications is us talking to cryptography people. The second point is us talking to the quantum people. So telling the crypto people there's cool applications here for you to build and telling the quantum people there's demand that you're not looking at that is coming. Um, that that's the kind of duality of those two statements. When you were meeting with the quantum folks and you were going to those events, you sort of mentioned it's a little bit corporate. I've only been to your event, which was meant as like a kind of mix of the cryptography people and the quantum people. But what sort of struck me with the quantum side of things was I got the sense that they're a little bit more like web two classical startups, too.

Like even if they're small, they're still like they're hardware. I mean, and I don't blame them. It's sort of they're they're dealing kind of with these hard primitives, expensive timelines. they they're going to have to think very long term in order to raise money and it's it's just like a very different business. Do you imagine sort of new startups coming out in the middle in that intersection having a different spirit? Like aren't they still going to be constrained by the same issues of like timelines and expense the minute they start playing in quantum? I mean first there's already these startups that have started emerging. Some people that helped co co-write the manifesto and kind of reviewed it were like people that are now started companies in that

space raised money from crypto investors and some some other are rising in that space. So it's it's already happening and what we found and what got us excited is that when we posted the manifesto it resonated with quantum people and they said I cannot believe that this was written because this is the energy we need in the space. A lot of these quantum communication people were like hackers in their past or were came into quantum communication because it was oh the most secure systems you know so a lot of them have that mentality and um the only reason they're not really embracing it is because where's the demand we can build these kind of systems but we don't know that there are new applications beyond the current ones and the current ones are this kind of defense related

applications or kind of very primitive applications that is quantum key distribution um or you have to kind of enter the fold of quantum computing and you have to serve their needs because this is where a lot of the narrative is both funding wise and also just hypewise. And so in a way we're kind of saying let us create a new narrative and some of these people are ready to jump ship and like to to kind of like slightly steer the direction of their company towards what they really believe in and this has been recurring. It is not like universal at all but there is definitely a set of people that believe that. That being said, you're right that there is this hardware component to quantum computing.

That's what I was gonna say. Also, you just you just mentioned quantum communication. Yes. And then there's quantum engineer like there's quantum computing. There's there's sort of like these different components that you learned on the last episode like are there some parts of the quantum space that are more flexible and faster? Are they all sort of stuck in the hardware side of things? No. So quantum communication is like let's say the supersets and then quantum cryptography is just secure communication in a way but you're using the rails the quantum communication rails. Quantum computing is more you could consider like local communication in a way where you don't need to necessarily share quantum state to another like quantum processing unit.

Um and then you have quantum sensing as like the third broad category. Quantum sensors my understanding is some of them are quite mature and used in some applications already. quantum computings are the ones that have garnered the most hype but um haven't really delivered on like useful applications yet. And so they're they're in that state, you know, somewhat blockchainy state of like, you know, selling selling a lot of um promises and people are excited about them. And the quantum communication side, you have some primitive applications and what quantum communication requires from what we've seen is very little kind of hardware for it to work for some applications. Okay.

And so part of the VA festo is kind of saying hey um instead of focusing on quantum computing and on kind of basing your timeline a little bit the way GML discussed at the beginning like being a skeptic because computing is far away uh quantum communication you can use today you you you know you you can use an optical fiber to share photon that you've encoded information in between two parties and you have these networks that already exist spread kind of all around the world that aren't they aren't huge and there's still a lot of work to do but this is kind a technology that we can start using at a at a primitive level. That being said, there's still this hardware component. And so, oh, relative to starting a cryptography company, let's say, where you can really It's still hard. Yeah. Yeah. I mean, you

have you have to you have to either build your hardware or you have to use someone else's hardware. And it is not deeply expensive to be honest with you. Like, um, you can build a very basic quantum network on your table, you know, like a few nodes or something like this. I don't know, Nico, if you have a price range, but like maybe 500K or like six 600k. Oh, not much. I'm surprised it's even that expensive uh just using like a photonic setup, but it the the most expensive part is the photon detector and then it depends on the application you're trying to do with it. The more kind of features you want your network to have, the more expensive it can get.

If you want the leanest, definitely cheaper than like six. Yeah, you could make a like a nice like tabletop for under 10K, I think. But like just it would be a demonstration of a cool thing, not like a useful necessarily. Or also depending on if you buy off the shelf or if you buy like parts that you then build yourself, that's a big component. You have hardware providers that you can buy off the shelf from, but there's a huge markup um on on on that obviously. Yeah. um if you're savvy enough to build it yourself then you can get the cost down to maybe 50k or 60k you know but all of this to say there's a hardware component you have to wrestle with it and that that makes it kind of cross-disciplinary to some extent a little bit more than cryptography because you need that kind of somewhat

hardware expertise or at least intuition and understanding of what's going on in that space and then also the understanding of uh protocols and cryptography I just want to add one thing which is if you're scrappy enough like a small startup. I think there is a big secondary market of these devices that are not used by the startups that are pivoting away from this. But I just want to say one thing which is uh one of the intuition that Alex and I had was that in quantum computing we have to wait for better hardware. And the question is do we need to wait in quantum cryptography for better hardware or can we use existing technology and it turns out that there are applications for which you can just use existing

technology. There is no new open question. is just a like Alex said, put pieces together uh or like have professional systems or professional u network operators that put these systems in a cloudlike facility. If you want to run like some nodes in a network to run some protocol on a quantum network, you cannot really do this today, which is crazy. Like if you we're coming from a web two web three experience where you can just deploy as smart contract or you can just open an AWS account and you have the cloud going for quantum communication you cannot just do that. I think we we are very close to get to

that point but we don't have uh easy to access quantum networks. If you want to deploy an application, most times you get told uh either to engage in a contract with some of these network operators or to talk to a university to give you some nodes. Like imagine saying this to a builder in the web three community. And so this this is like the role in a way of the quantum punks movement to say hey guys there is a whole community that can grow out of fiddling with things or hacking on things on open-source software and uh there there are players in the space that are thinking the same way as us and uh this is very exciting and so hopefully we do our our little to change

that mindset. I want to dig into two things. cuz one of them would be like more specifics around what this thing is like what what this would enable. But but number two I I want to point out something kind of funny, right? Which is the an like the anthropology here like I mean the culture of like physics and physicists from like PhD labs who know this stuff is in some sense completely different than the anthropology of like the you know 10-year-old programmer who grew up to like want to do cryptography things, right? I I I don't mean that in like a deterministic sense. I don't mean like it's always the case. It is just kind of funny, right? Like you go work at a physics lab, you have all this very fancy equipment that's like, you know, millions upon millions of dollars.

There's like a certain scrainess that comes from that. But there's also a certain thing about like, oh, we have to do, you know, things the way that they were intended to be done by like the previous like, you know, generation of physicists who entered this lab. Uh, and it's kind of interesting. I mean, it's not not everyone's like this, of course, and there's like weird pirates out there who like just go and build for fun. Uh, but anyways, it's it's kind of interesting because like it's it's kind of like a slight cultural distinction uh of the two. I think the other thing that I um want to point out, which I I you know, when you say it, it sounds so kind of trit, but it's it's like very neat, is we now have the technology, even if it's not 100% perfect, but we can build

real things. um is like again like a weird ethos thing, right? Like a lot of people who come into this field, it's like a very particular field. Uh you know, like cryptography was a thing that you wouldn't teach undergrads up until pretty recently because it wasn't it was really written in papers. It wasn't really written in like a standard way, right? You got to go do a PhD on this thing. Like physics is kind of still that way, right? Like doing real like deep quantum stuff like kind of requires you chew through a bunch of papers and stuff. like you have to be further along in your academic career to get there.

Yeah. It's like hasn't been systematized enough to make it legible for people who don't want to stick out this like long journey. So it like almost self- selects for this interesting like person who is kind of willing to true glass for a long time before they're able to kind of get to the top. Right? But but as it gets systematized because technology gets better, people get better at explaining these things, we have better abstractions for the thing. Right? Now this layer, this intermediate layer of like kind of crazy pirates who just like come into the field. Yeah, exactly. Want to just build things are like I see where this is going and we can start building it. Just like becomes like in other words a field becomes legible to like this like higher level like people who are just like willing to like

startups around this stuff. Um just like comes in and I think I mean obviously this this doesn't happen in a vacuum, right? Like you guys are part of this in like writing this manifesto, right? like you're making the field legible to people who are not simply like you know seventh year PhD students working on a transducer or something. Mhm. I kind of agree like not only I think that uh quantum cryptography just to um give you context it is a very small niche field. Yes. At Qrypt there is which is the main quantum cryptography conference I think there are 300 attendees. If you do like maybe a rough estimation of like one to5 professor to student ratio maybe this ratio is wrong I don't know but what I'm

telling you is that you cannot have more than 300 experts in quantum cryptography and some of these people are not even computer scientists they are physics people they are trying to quantry no but there is a broader community of uh experimentalists that are trying to build these systems in practice and so not only is it very hard to work on these things but The combination of these two fields is an insanely small niche. Yes. And so the drive that you need to have in order to be working in in in this intersection, it's very strong. But in a way, it it reminds me what happened in the early days of cryptocurrencies. You had people that you needed to be an expert in in a way in cryptography. Like in order to

understand cryptocurrencies, you needed to understand consensus and what it meant or or in order to work on zero knowledge proofs, we need you needed to have like a body of knowledge that was a there was no short summary of what these things were or like an easy explanation. There's no ZK podcast. Yeah, there was no ZK. Well, actually when ZK podcast started, I think it was still like that. But yeah, I mean I think Anna, but you you you contributed to making it more legible. This is exactly it. Yeah Anna like you are making this legible you know 100% in the early days of cryptography you need to have a strong understanding of cryptography a strong understanding of economics and then a lot of imagination and so this is the point in which we are right now the

field is not empty there's a lot of theoretical quantum cryptography which is very exciting and there is the beginning of applied crypto quantum cryptography we have QD we have it for like more than a decade now. What's it called? Web, what did you say? Oh, QKD. QKD. Quantum key distribution is the let's say the only practical and piece of technology of quantum cryptography that that is sold today. Okay. To final users. It's it's about we can we can talk about it in a second, but the thing is there is just that and we need more creativity and more intersection between these two fields. I want to dig in a little bit more into kind of the previous thing we were talking about

which is okay let's say we have you know the AWS of like quantum communication over short ranges or something whatever I mean feel free to place whatever constraints you want on it and you could launch you know there's some nice abstraction for what this means and all this stuff which are questions that are outstanding but what can we do with that you you could launch like a service that like does this thing for you you know like what are some things that might enabled. Like that might be interesting that people haven't done yet or maybe that people are doing but like on a lab setup as opposed to doing it, you know, out in the wild with some like cool code that like executes a thing out there, you know. Let me let me start with the maybe with the North Star. Okay. And

then we can go back into like uh what you can do. And this is also helpful to give an intuition of uh what we're talking about. And most importantly uh it's a way for me to spread a meme which I think is very strong and it's quantum money and most people in physics or in cryptography unless you work on quantum cryptography you're not aware of what it is and I find it uh quite surreal. So in the 60s there is a Wisner the the first quantum cryptography researchers that writes a paper that sits on a shelf for 15 years rejection after rejection uh 15 year plus actually and then at some point in the 80s this paper gets published and it's called conjugate

coding and in this paper he talks about like uh two main examples of like ideas that you could do with this and one is quantum money and we're talking about like 25 years before Satoshi Nakamoto wrote uh the the Bitcoin paper. So this quantum money kind of this idea of quantum money which I will describe in a second predates uh even the cypher punk movement. So it's in it's incredible that a person had this paper on some shelf that talked about uh peer-to-peer money and at the same time started a field of quantum cryptography. So let's talk about quantum money. Before we talk about quantum money, let's talk about physical money. In a way, gold coins. I

have a gold coin. It's in my pocket. I give it to you, GMO. In that moment, you know, it's in your pocket. The transaction is instantaneous. It's private. There is no third party that needs to be notified. What a great piece of technology. Mhm. The only issue is that you cannot send it over the internet. And so, we need to meet in person. And this like this physical annoying thing. What we want? We want digital like communication. So that's why we went from physical money to digital money. Digital money is like a file that you encode money in a file that I send to you. But at the same time, I could send to Anna and that's a problem. Yeah. So

we need to make sure that there is someone else a third party let's call it a bank that orders these transactions or or or like so all in a sudden or yeah exactly or you can take the bank and distribute the governance on uh many people with proof of work and that's a blockchain. So even blockchains like uh don't remove the bank they just replace the governance of the bank and this is the problem of digital money because I can send the same file to two people. Yeah. double spending essentially. And so the question is, can we build money that can be transferred in a digital like form that have physical-l like properties? Meaning that once they send

it to you, they leave my pocket, they enter your pocket, the transaction is settled and uh no one needs to witness it and it could never be cloned or copied. Correct. Yes. Absolutely. So and quantum quantum money uses properties of physics like the no cloning theorem in particular which essentially says quantum quantum information cannot be cloned once you receive it and so you cannot try to look into uh the information say stored in the quantum state like preserved in the quantum state because the moment you you try to look into you disturb the system and then you lose information and so if I couldn't code money in a photon

and I could send it to you. It's like from my pocket to your pocket. Then I cannot send this money to send these photos to someone else. The issue is uh where are you going to store these photons? We don't have USB sticks for photons yet. Wow. And so that's why I said before, you know, this uh directionally is the north star is one of the applications that we can look into as northstar and it for sure is an application that a lot of web three people can resonate on. In a way is a very cipher punk application. Totally.

This by the way like in our episode with Yelina, we did cover teleportation and the no cloning theorem. And I'm guessing that's what you're discussing here. this like is that teleportation in a way because it like it disappears on one side and appears on another. No, it would just be no cloning. The teleportation part happens in repeaters. So because this no cloning thing uh most people would tell you that it's annoying because they will tell you that in normal networks you repeat a signal over so that um you're able to amplify the the information that you're sending because you can copy it. And so that allows you to send information far far away. In this case, if you're trying to amplify this photon, you would have to

to copy it and you're not able to do this. So you have to build a different type of amplifier and different type of repeater. This repeater is based on it's a entanglement swapping based. And so you use this teleportation property. Oh, okay. Um kind of like uh transitive maths if that makes sense. Like A to B to C. So you do you can do A to C where like the B parts you do this teleportation thing which is teleportation is just a cool name for it. It is a pretty sick name actually. It's it's it's an awesome name. It's a it's a good advertising department name you know like teleportation. The way to think about it is that there are two different layers of the stack.

One is teleportation is useful for the networking stack in a way. If I have the photons that I want to send to you, uh, I can send them to you directly or I can use alternative technologies to send this quantum state to you like a quantum teleportation. I see. Yeah, it's the in between. So, does it really have to do with how far away you are? Like the distance? Yes, exactly. The again uh let me let us preface some of this with the fact that uh you should see us as crypto people that are entering the quantum space for the last year and that are like learning. So we are maybe further ahead than some of the listeners uh but we are still uh learning. My my my understanding is that the photon gets

absorbed in the optical fiber uh at at about 100 km. It gets absorbed before even but 100 km is kind of the distance of after that you need some form of repeater. Um you have trusted repeaters that actually decode the information, read it and then reissue a new photon. But then at that point uh it's trusted so you kind of lose a lot of the the cool properties or you have these trustless repeaters that are based on entanglement swapping. Um teleportation ex Yeah. Ex and then it's teleportation. Um got it. So the trusted repeaters is what a lot of QKD networks today are using and the trustless repeaters some of them are built but they're they're quite primitive and there's a few things that they need to to improve. Uh, one of

those things is what Nico mentioned before, like storing the photon for a little bit longer. So, slightly better quantum memories helps this like repeating process to happen or if it fails, you can do it multiple times because you're still storing the photon. Basically, I have two like maybe slightly like lower level questions and it's okay like feel free to not answer them if you're like ah this is too stupid. The first question I have around it is surely we can use the no cloning theorem, right? we have some thing in some state, right? And like I just like give that to you, right? And be no cloning. We can certify that I like cannot like clone that. I can't just like have that in my pocket and give it to you. The problem is like we need to still verify the thing you've given me

is money, right? As opposed to just being like some arbitrary like madeup, you know, new state, right? And to do that, we have to measure it. So how do you ensure like when you measure you know this piece of blob that hopefully is money but you do not know if it's money right uh you destroy part of it right that's this is like the same reason why no cloning is a thing so how do you ensure that like the blob I've given you which could be you know could be a hopefully is a coin in my pocket but actually could be some madeup nonsense that like vaguely looks like a coin in my pocket uh how do you ensure that's real a real token. As a computer

scientist, the formal answer that I would give you is that there are protocols that define this property as a local verifiability, which means that um uh there are some quantum money protocols that you can locally verify meaning that uh I I don't know the physics uh part of it. I I don't even know if we have constructions for it. But uh technically people have been thinking about this problem. I I'm a slightly more expert in say private quantum money. So quantum money we cannot have them today mostly because we don't have memory. So thinking too much about quantum money it's a bit of a problem. It's something I really want but I cannot have for until we have innovation in quantum

memory and so but what we could have in the short term is a private quantum money. and private quantum money. It's not something that web three people will be insanely excited about. But the idea is that as long as you have I call it a mter but you can think of it as a bank uh or like a node that that is a trusted node the mint token. What you can do is uh you can ask the mter to mint tokens on request and you can engage with the mter in a protocol to verify that what you have received are quantum tokens. H but this requires interaction with interaction with the bank. So I'm not aware of any protocol that gives uh local verifiability in private quantum

money. But there is a way to do that. You know what I'm saying is worst case as a super applied pragmatic person and tell you well worst case just talk to the bank and the bank will engage in the protocol with you in an interactive protocol to they will verify the the tokens. Maybe maybe Nico it's worth uh instead of looking at quantum money explaining how like quantum key distribution works because like I think the question of GMO is like the more basic like hey this this information that I've encoded in the photon sure it's it's temper resistant if anyone intercepts it they can't read it but the ultimate um receiver of that information how can they then read that information yeah of course so again like uh Alex

said let me put a big disclaimer here which is a I'm a computer scientist and uh I don't come from uh quantum cryptography but I'm here to learn and and be corrected. I also gave a presentation in the past where uh a professor told me well this triangle that you drew is incorrect and I was very happy about that. So if you're listening and I say something wrong please reach out. I want to become a better um quantum cryptographer. So the idea is the following in QD is the problem of quantum key distribution. So before cryptography you and I want to encrypt a message so that other people around us like an eavesdropper called Eve cannot listen to our message. So before uh

let's say modern cryptography the way we did it in an information theoretically secure way it was that we we come up with a long pad of numbers uh 0 1 0 1 0 1 0 1 that we used to shift the bits of our message but when we come up with this one time pad we need to meet in person to exchange it because there's no way to exchange this one time pad in a secure way so this this like a let's say clo shon cryptography and then defy Helman showed up and they said well there is a way to do key exchange but you need to add assumptions you need to assume that some problems are hard for computers but the issue is that these protocols are not they're not

resistant to quantum attacks because the quantum computers can quantum computers can break the discrete log this hardness hard it's hard to find the solution it's hard to like you need endless amounts hours of computation in order to solve this problem and now all of a sudden a computer comes along where it can do it faster. Yes. So the crypto I like to introduce like a new meme that I like a lot uh crypto mathematics and crypto physics because the word quantum means so many things. If I say quantum cryptography a lot of people will misunderstand it with postquantum or quantum cryptography. So let me just like simplify it for everyone. There's mathematics there is b this crypto this cryptography that is based on

mathematics or what I mean by this is a simplification is based on assumption of some hardness of mathematical problems and that's the cryptography that we used and some of it is postquantum some of it is not and the one that is postquantum like we don't really know we think it's postquantum yes exactly exactly exactly postquantum until it's broken yeah yeah and uh it it could be that we didn't even we didn't even have to wait for quant quantum computers to break some of these postquantum security. We've seen it with isogynist in the past few years and we saw with some like uh assumptions in latis and so on but anyway so going going back there is a cryptoatics which

has mathematics as assumption and then there is cryptophysics there has physics as assumption and so we have this one time path but we have to meet in person okay then we have there's a modern cryptography defman but uh it's broken with uh with the quantum computers so the question is can we build a way to exchange secret a secret key so that we can later encrypt our messages that uh does not rely on mathematical assumptions and instead relies on the laws of physics. Okay, this is the the the hypy way to say this but and and the way it works is like this. Uh so there are two parties uh each of them sample quantum state and I'm going to explain

for those that want to look it up later on the BB-84 protocol and uh it's like a like a milestone paper that is a subsequent paper on the conjugate coding paper from whisner and so in BB-84 you encode information in um in say in quant in a quantum state which could be in the form of photons and both Alice and Bob uh sample these BB84 states and then they send them to each And then after they receive each other's each other's states, they measure it. But the beautiful thing about this BB-84 states is that they can be measured in two bases. So Alice encodes them in a specific basis and Bob measure it in a basis that is random. So sometimes it's

the same. If it's the same, they're able to extract the information that Alice sent them. But if they don't use the same basis, they will get random information. That's the property of of quantum. And so they engage in this protocol and then they talk with each other in a classical in a public classical channel and they say which indices of this BBT4 states they read in the same basis and then there is like some other protocols to figure out like uh if EES was was in the middle and so this is an example where you can use the property of uh of quantum states and in practice it is the the Heisenberg uncertainty principle where like you don't know in which basis

the information has been encoded and you can only uh know if you happen to measure it with the same um with the same basis that has been encoded otherwise you get uh random information. Yeah, I guess ve very quickly on that point right like the idea behind the random basis is these are these will function as your par check bits to make sure that there is no eavesdropper if I'm if I'm getting that correctly right so yeah so the the the technicality of the protocol is the following is that some of the string we measured in the correct way and we keep those bits the ones that we didn't measure correctly we put them on the side and then we're trying to do some sampling to see uh if there was uh some ifs dropper because if there was some ifs dropper they would

have taken the message in between but because you cannot clone that message you cannot ret copy because the moment you try to measure it if tries to measure the quantum state then they would not know the bases themselves and so when they send a new quantum state which is like a fake quantum state this with enough sampling can be spot it's like a there are in total four chances and the the probability is like three four or on the power of n. Yeah. Yeah, for for the like again for the people out there this like think of it as like you can send some stuff which like depending on how you measure it will be either information that you get which you're encoding via some error correcting code so you can always decode it or B you're going to get some checks

someum bits and the checksum bits will like the statistics of the checksum bits will indicate whether there was an eavesdropper on the channel because by construction by no cloning specifically we have this weird property that like if Eve measures the thing on the channel she will change the statistic of what the outputs are, right? So what Bob will see will be like a different like statistically quite distinct. So this is the same thing as like we do in ZK proofs, right? In ZK proofs, we have this like thing where we have a bunch of like a huge message and we sample little bits of the message and we check that they're consistent with like some underlying set of operations that we expect, right? And we do this via correcting codes partially and then we do this via these like weird proximity tests or whatever. We're doing exactly

the same thing here except like we're doing a similar statistical test here except one is like over one basis and then one is like over like the basis which actually gets you information and one of them will tell you whether there was an eved dropper while the other one will tell you what the actual message should have been. So that's roughly like mapping it down. I think for any listener who heard our episode with Yelina we did actually talk about a similar case in that one. Exactly. You've talked now about a couple of these applications, but I feel like in your exploration of this intersection, are there other things that you've discovered are possible even theoretically at this point? Yeah, for sure. I'm going to say some and I'm sure Alex has a has a bigger list. There are some things that you can do beyond

quantum key distribution. There's a this private quantum money solutions that you could try to experiment with. And then more broadly in theory we know that we have new kind of uh if you also had compute you could enter like a a new realm of um application. So for example, there are digital copy protection programs or um well copy protection programs. Um essentially I can give you a program that you can run but you cannot make copies of and so you can give it to someone else but you cannot make copies of and uh in a more say extreme way there is uh this idea of one-time programs. Unfortunately, you cannot have one-time programs without

hardware assumptions. One-time programs are not possible neither in classical nor in quantum. But uh with with uh some trusted hardware you can have these onetime programs and there are some groups that are that are working on this onetime programs and uh and the beauty of it is that you could encode say financial uh for example you could encode an option in a program that I send to you and then you can decide whether or not to exercise the option without talking to a ledger or without uh talking to anyone. And this program only runs once. So this is a a cool idea definitely has could have a lot of impact and then you have other uh applications one that I find very interesting is a quantum position

verification this like a GPS yes yes yes it's like a physically based GPS but what what are you trying to you're trying to say that something is somewhere how would you do that uh so in in in practice you play on latency because you cannot uh make information travel faster than light that's that's the principle The question is what's latency? It's how long it takes to get somewhere. Okay. Yes. Yes. Yes. The the issue with it is uh building this in a secure way. It's uh very hard. And then there is a I don't know other problems are that come to mind is a quantum random number generation. Mhm. And in a more broad sense there is this concept of device independent cryptography that

you could apply to all the things that I just mentioned before. You could have device independent QD, device independent quantum number generators. Device independence means uh today when you if you run a protocol, you need to trust the machines that you have that is correctly running the protocol. In a way, when we buy a ledger or like a hardware wallet, we don't know if it's running correctly. Yeah. The nice thing about device independent cryptography is that you can test the ledger to see if it is uh correctly executing the protocol which is pretty exciting because all of a sudden you don't have to trust the hardware. I don't really get that though device independent like what what makes it independent of the device like maybe I just don't fully understand what the connection that

exists now is. Um so I'm I'm I'm not uh I'm not entirely sure to be honest. This is one of the more extreme things actually at the event that you came to there was the inventor of device independent cryptography that gave a gave a talk. Okay. Roger Roger Belco. My understanding is that you're able to be qu you're able to basically query the device and um you're quering it in a specific way. You're trying to see if there's a a belt inequality violation that tells you you're you're trying to without the technicality which I'm I'm not like super familiar with. You're trying to test whether this device is really a quantum device. And if if if it's not uh then you know that it's being either tempered with or that it's faulty. If it is, given the output you give it, it's going to give you given

the input you give it, it's going to give you a certain output that's going to tell you, oh, okay, this is this is legit. Uh and so for that reason, it's device independent in a way because it doesn't mean you don't use any devices, right? Yeah. It means you use a device, but it means you can ask the device before like, hey, are you are you messing with me or not? And you know that whatever answer it gives you is a true full answer. Okay. I think when you said device independent, I thought it was more like some program can like exist on multiple types of of device that are very different from one another. It is it is slightly confusing.

Yeah. Yeah. What it means is really like you're removing it. It's like trustless hardware in a way. So the way this this person Roger explains it as well, he also says now you can have uh quantum hardware made in factories that you do not trust and you're still able to check whether the hardware was tampered with or not. Or you can have someone else run the hardware somewhere else and you're able to check potentially remotely if you have like a quantum connection to that hardware that the hardware is running correctly with some probably things that I'm missing here. Are you using the e is this the same as we described before where like if someone has eaves dropped it's different is that what this is playing on exactly same idea so the way to think about it is imagine hardware that does two things

number one is it spits out a zk proof that like the output is correct and number two it also spits out a roughly speaking quantum proof that it has not copied any of the bits anywhere else into the machine okay because if you were to do that you would be with the statistics of the underlying thing. Like this is not quite a perfect analogy, but that's like the best way to think about it. It's like what is the problem of a machine right now? Like the machine itself could be doing all sorts of nonsense and sending out data to like other things. There's no way for us to know that in a digital world. Yes. Right. Because again, you can copy data, you can send it out, you can keep it in a bunch of stuff, you can do additional processing on it, and you would never

know unless you like knew how the machine worked. But we can prove that the output of the machine is like correct like the output that it hands you Anna, right? like is good by just like giving you a zk proof or a sync proof or whatever. But now again we we now don't know this property of like we can't copy out things from the machine. Yeah. Right. And so the like big brain version of this is like okay sick but like here's like a cool thing that like guarantees that people haven't done copying of this underlying state because if there had been any observer you would get a different outcome. You couldn't make that proof. So in some sense like it it like again it's not exactly sync proof like it's like a fancier quantum thing that you can do with this but fundamentally the point is the same.

It's like you know the computation is correct and you know that nothing else has been done because if anything else would have been done like it needed to like observe the data that is passing through these pipelines for it to like go out and like give you the right result. Nice. So there you go. That's maybe like the analogous like weird cool conglomeration of the two things. I don't know if that scans Alex or any No. Yeah. I mean, I think that was great. Um, what's what's exciting about it is, um, you know, if you think of the current movement in the blockchain industry of like trusted hardware, you could think that the endgame of trusted hardware is you don't you don't have to trust the hardware at all. If you know that's a like a mey way of saying it, but I think that's it. So I think you

know some of the people trusted execution environments trusted trustless trusted execution environments I just added another trusted like we add another zk but yeah you know I I think I think I think that could be very very exciting. Obviously there's a lot of limitations to this. There's like extra overhead involved in like a device independent protocol. Uh again that's that's my understanding but my understanding is you could make them better. You could improve those protocols if there was like demand for for doing that. Um and so again from the point of view of the crypto industry and the point of view of some of the problems that the trusted hardware people are facing right now which is well these chips are fabricated in you know by large corporations we don't have access to them like they might have back

doors in it. Exactly. Exactly. And this is this is kind of saying well let them build the hardware um and we're just able to test it independently. you have similar things happening where you're able to test hardware with like um infrared scanners. I I don't I don't know if you've heard of this. This is not quantum anymore, but this is still cryptophysics to some extent where you're you're able to scan the chip to understand if like anything has been tempered with. I don't know the details, but there are people working at that intersection as well. Sorry, this is like a side note to what Nico is was saying, but there are scaffoldings towards quantum hardware that starts from more traditional hardware that just improves this trust guarantees over time and that is quantum inspired and there

are people working on this. Um Silvan for example if you if you've met him before um is is one he wrote this paper called a path towards cryptophysically secure trusted hardware um and with a lot of which project he was at IC3 uh and now he's building his own company around this uh and kind of building this trusted hardware and improving the guarantees based on different physics assumptions you can make uh on it. So that's one exciting thing, device independence. I think Nikico mentioned a lot of other primitives that are cool.

Yeah, some of them are based on unconability, some of them are based on entanglement as like the two key primitives. And then you can kind of you can build cool stuff with uh each of those kind of things. Um one that I will shout out for GMO and that I don't know a lot about Oh god. is you can use you can use entanglement for coordination and to play you have to put a correlated equilibria versus uh playing to standard Nash. Yeah. And so there is this paper called quantum bidding in bridge where people say that if if you if two players that are playing together in a bridge game uh so this is not blockchain bridging. This is like the the game of bridge bridge card game. Okay. Exactly.

Exactly. Grandparent game. And if if they if they have uh if if they share an entangled photon, they're able to win uh more frequently because they're able to coordinate better. So there's this kind of overlap with like kind of game theory or like some some of like advantages in games and entanglement. That's quite interesting. Some people have started to think about it in the context of financial markets for some specific use cases. uh which is mostly theoretical but that's an interesting intersection that I don't think um people have been thinking a lot about practically but that is also exciting in the context of using entanglement as a primitive and to to go back to a previous application that uh Nico mentioned the same way you have copy protection you can also have

certified deletion so this is all playing with the same concept of unclonability but in in in different ways and for each of these sub kind of use cases you know if you have a little bit of imagination you could potenti potentially think of things you can do with that, right? If you can prove that you've you can certify you've deleted something in a verifiable way, uh even if the those two parties do not trust each other, it augments our communication kind of systems with new ways to communicate with one another. And so again, from a crypto minds perspective, it's kind of like uh like being kids in a candy store. Y so many things to play with. In a way we started with a northstar which is a it's not the only northstar but it's like an exciting

application which is quantum money. Then we discussed like some applications that are more broad than quantum money but only some of them unfortunately are practical today. So what I'm trying to say is I want to excite the listeners but I also want to give caution which is uh the only thing that we know is practical today meaning you don't you don't have to come up with new hardware. It's QKD, but there are a few others that could be implemented today. And one in particular that I care a lot about and I'm trying to uh talk to everyone so that everyone knows that this is possible is uh this paper from Orsat and others which by the way are also has been in the show. Yeah. Yeah. Great episode. Is the uh tokens for MAC and

MAC is this primitive of uh in cryptography which is a message authentication codes. The the idea is uh I give you a code that then when you give back to me I can verify that I gave you the code. H and uh this is used in many places but the issue with the authentic uh MAC is that uh I can only generate these authentication codes myself because I have the secret key to do it. Imagine for a second I want someone else to generate an authentication code on my behalf. M the naive solution would be give them the secret key. You understand that this is a not good because then they can generate as many authentication code as

they want. And the beauty of this paper is that uh it introduces this idea of uh tokens that can be spent quantum tokens. So quantum state that can be spent and by spent I mean measured in a specific way so that they you can generate one Mac only on my behalf. So it would would work more or less like this. I create some quantum states, some photons. I send them to you. If you had memory, you would keep them until you need them. But without memory, you would spend them straight away. And by spend them, it means you would measure you would uh measure the the quantum state that I sent you to generate an authentication code. And you can only generate one authentication code only. One

application of this that we have in crypto is actually from my for former project flashbots. We want to offshoot little toy project that they did. It's called teleport.b best. And using trusted hardware but not not quantum stuff. But again with trusted hardware you have some quantum some like uh phantom quantum properties. you they were able to create this this platform where let's say this marketplace where I have a Twitter account and I'm able to sell access to my Twitter account and to a single tweet that other people can buy this token and they can spend it to write a single tweet um from my Twitter account and I don't have to reveal any information about my Twitter account to them and they don't have to reveal who

they are as well because they're using the properties of the trusted hardware and you're using some form of unconability um in that in that sense. So again, this goes back to the point I was making before where one path that you could see towards the crypto space becoming more quantum pled is through trusted hardware to some extent because trusted hardware offers you some quantum inspired properties. And so you could think of building applications that are kind like teleport.b best which is more of a toy application than anything else but you're you're already building the the user expectation around unconability and then you're able to just improve the guarantees behind it. Uh that's one thing I'm excited about. Anyway, that's one toy application, right? But it's cool that it opens up this market. Now

you can use it and you don't have to fear well assuming you trust the trusted hardware. you don't you don't have to fear that someone is going to get your your Twitter account and you're able to sell fun access tokens to your to your Twitter for like one tweet and you're able to do cool stuff with it. Um so you can imagine maybe that for more useful applications but that's one way to apply this practically that that kind of made sense and that went slightly viral and people started using it at least for for a short amount of time. The beautiful aspect of these uh tokens for Mac is that you're creating this new concept of a physical resource that gives you access to something. Uh it is a almost like a capability in distributed

systems. The concept of capability is a it's very fascinating which is if you want to write into a file uh you need to be generally there's like a list of people that can write into the file. In capabilities based systems, someone gives you the capability and you can give this capability to another process but the process can write into the file as long as they have the capability. So this idea of capabilities I think it's um very synerggetic with this idea of uh tokens for Mac. You could move around this token to whoever they need it but they can only spend them themselves once. With this idea, I gave a presentation at uh the quantum punks event we organized in Paris on like

directionally how you could be building quantum based uh layer tools in in a ways you can think of it as a as like an instance of a private quantum money and the idea is we could be building a bridge from layer 1 into a quantum network where in this quantum network I could move these tokens around and whenever I'm done transacting I can settle them back into the layer one. It's a it's a bit complex. So I would probably send the listener to go watch that video. And unfortunately there's not clear protocol yet. But uh I would love for new brains to go and trying to find where are the intersection between what's possible today and

cryptocurrencies because our whole thesis is that if we find an application like this we could accelerate the space like uh we did for zero knowledge proofs. Wow. Are there any other like open problems or areas that you're brainstorming about or that you've noticed people are working on? So there's a few. Number one um to to to keep it short as well is whether we can allow people to remotely and classically connect to quantum networks. And so this would bypass the hardware uh constraint entirely. Right? One of the criticism that you guys might have uh for quantum cryptography is that well I need quantum hardware. this is going to be super expensive, hard to get expensive and

like it's just a friction, you know, it's like a hurdle that I have to overcome and so I need to be motivated to do this and that's friction that kind of drags people experimenting with it, etc. Um, and so one thing we've we've been looking at is could you at home classically connect by classically I mean with your computer in classical communication connect to a quantum network in a way that is trust minimized or in in a way that you would you would be able to fully verify whatever operation is done in the quantum network was done based on how you wanted it to be done and a in a in a way that's privacy preserving as well. So there are protocols uh that are called for example remote state preparation that are they're very inefficient protocols but

um that kind of start going in this in this direction of thinking about okay how can I how can someone remotely prepare a state for me and then remote state measurement would be the the the other side of this and so you can do this in a trusted way today right you can it's just an API where you're you're able you just need to talk to the quantum network and it needs to prepare the photon the way you want it if you trust whoever is preparing the photon that's that's easier. And so that's one thing that we're excited about because if you manage to do this well, it can start trusted and then it can progressively improve its guarantees. We get into a new paradigm for quantum kind of networking and cryptography where now GMO and and and you can hack on quantum networks via your classical computer.

And so that I think is like one hurdle that we see as potentially accelerating things and that's very achievable at least the trusted version of this delegation verifiable sorry trusted delegation achievable in like 3 months very it's like just a matter of this software that's needed that's my understanding if you want to do verifiable then you need actually cryptography work to improve the protocol and um that's a little bit more complicated but um I imagine that this would be something that a lot of cryptographers and quantum people would work on if there was kind of this this demand for okay now if we had this particular thing that's verifiable and if we can improve the overhead massively by some math tricks or some application

specific verifiability I think they would start thinking about this more if there was this this kind of use case so that's one thing I think we're we're exciting about as a problem because it is shortterm it accelerates kind of the the pace of the of the space it's a very concrete kind of developer experience problem in a way and it also pulled on our at least more Nikico than my expertise but like you know verifiability and these things are like problems that Nico had to look at in the context of fiocoin you know in proof of storage and these things like how can someone prove that they have you know storage somewhere else I was wondering if um you had mentioned sort of there not being quantum memory are there is there anyone working on quantum memory yeah so there are people working on

quantum memories and actually at the event in Paris there's one presentation on it maybe we can link it in uh in the description of the podcast. Yeah. Are the videos out for that? I just uploaded them. I need to add the titles. They're not like public public. I need to put the titles on them, but they're all Maybe by the time the episode airs, they will be though. 100%. Yeah. Yeah. Perfect. Okay. We'll add them in the show notes then. Great. Nice. So, people people are building quantum memories and um they're building kind of different flavors of quantum memories is my understanding. So, there there's different ways that you can trap this information. Some ways like purely photonic where you kind of trap the photon and you're trying to keep it and some ways is you convert the photon to another object and then this object is

more stable and then you're able to keep it there and then the challenge becomes now you have to reconvert the object back to a photon later and so this this conversion patter called transducers right GMO briefly mentioned transducers early earlier yeah we also chatted about it in the previous episode as well uh because this is Yel and has been working on uh for a while so I mean it's super exciting this is a technology that is needed for quantum computers. And so people are working on quantum memories to help synchronize multiple quantum processing units that are connected together. So if you think distributed quantum computing, you need to synchronize those units together. And to synchronize them, you need for a short amount of time to kind of like hold their their state together. And so this is where the memory comes in. And so the

unfortunate thing is that a lot of quantum memory companies that we talked to which by a lot I mean like five of them but it's big in that space um that were you know distributed all over the world what they told us is they started as a quantum networking companies improving the capabilities of quantum networks and what they found out is well there isn't a ton of demand for kind of better quantum memories. However, in the computing in computing land, quantum computing land, there is demand for it and we have these clients which are quantum computing companies that are willing to pay for it. And so, some of them have slightly uh steered away from the pure networking applications towards the it's still a networking application, but it's to connect quantum processing

units in data centers next to each other, you know. Um, so people are working on this and some of the results that they have are super encouraging as well. But so that's that's another problem that's that's hard and like difficult to deal with. And it's funny. I mean it it it feels a lot like memory just like in classical sense, right? Like our memories used to be like literally magnets with like wires that cross over and you could only hold them for a long enough time. Then afterwards there were these acoustic uh bits actually where you would encode bits as like a traveling sound wave that would reflect a few times and you'd have to like measure it on the out. I don't know if you guys know about this like the I did not know that. That's amazing.

So, it's like it's funny. It's like the same thing, but you know, we used to have this for bits in digital in the digital world too, right? We couldn't just hold like holding bits is like a weird thing. Like yeah, you could kind of read them and write them down in a way that you can't with quantum state but it's like very similar like doing anything more than you know a few things like turns out to have been really hard up until like shockingly recently. No, I I think part of this journey what has been interesting is kind of looking back at our our stack the like the normal internet stack and realizing how complex it is and how like how much improvement uh has it has undergone over time uh and how much it's like super technically complex as well and so that has been

fascinating and and very interesting and also encouraging to think that well you know this took time kind of what what you just mentioned GMO to to to close on quantum memories. Why it's exciting, why it's a high leverage kind of technology to develop is because you need them for repeaters. So if you have better quantum memories, basically the longer the quantum memory is up to some number of of of time and the number of photon the the let's make it simple. The longer the quantum memory is, the bigger the network can be. Basically h what's what's interesting is there's there's kind of a there's like 1 microcond 1 millisecond 1 second maybe 1 minute and then at the 1 minute mark um you get to like the covering the whole world and

then from 1 minute onwards my understanding is you don't have a ton more things and so to get like persistent memory this is what I don't understand but for quantum money I I my understanding is you need some form of persistent or or some something that can carry over and So uh that's an interesting thing but it's a high leverage issue for for that reason where um you can enable multiple things if you have better quantum memories. So that's number two in terms of like cool problems that I think we're we're looking at and we're interested in the quantum memory one is more of a like research interest. The first one is more like hey if someone builds this you can enable commercial activity and at least like hackers to start building. But yes, I maybe to give the just the the the just the very quick like mental model.

There's one that's about how can we enable people to build on quantum networks faster and there's another kind of camp that is how do we improve those networks in terms of their capabilities, the memories, the distance of the network, the compute capability which is related to transducers as well. Um, and so those are kind of the two broad areas and the first one is more interesting in terms of if you can catalyze activity in that first one, we think it's going to impact that second one. Nice. Amazing. Alex, Nicola, thank you so much for coming on the show and covering that intersection between quantum and cryptography, sharing with us so many of the applications that are already being considered, those of the future. This

has been super interesting. Thank you so much. Thank you guys. Super fun. Thanks for having us. Hopefully soon a quantum crypto podcast QC podcast crypto punk podcast. Yeah. I I like if if I have one contribution to like the meme is I would say how about computational cryptography and physical cryptography are the two distinctions. There you go. Oh, I like that. Cool. Well, thanks again guys. I want to say thank you to the podcast team. Rachel, Henrik, and Tanya. And to our listeners, thanks for listening.

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