Pop Quantum

Transcript

Miranda Volborth: 

This is Rate of Change, a podcast from Duke University dedicated to the ingenious ways that engineers are solving society’s toughest problems. I’m Miranda Volborth. Today I’m talking with two PhD students who I’ve lured to West Campus from the quantum realm, i.e. the Duke Quantum Center in downtown Durham, North Carolina. 

We’re talking about the idea of quantum in pop culture—what it gets right, what it gets wrong, and why it even matters. 

Andrew Van Horn: 

Hello, I’m Andrew Van Horn. I’m a third-year PhD student in Jungsang Kim‘s lab. My focus is on the classical control hardware for quantum computers. 

Debopriyo “Debo” Biswas: 

I’m Debopriyo Biswas and I am a fifth-year PhD candidate in the Duke Quantum Center. I’m primarily advised by professor Chris Monroe and co-advised by professor Crystal Noel. My work in the lab is as an experimentalist—I work on a trapped ion quantum computing system capable of controlling up to 32 qubits, and I’m interested in applying quantum computers to physics simulations and other problems with scaling quantum computers.

Miranda: 

So you’re a content creator, actually, on YouTube, and you focus on explaining a lot of physics science concepts to non-technical audiences. What does the word quantum actually mean? 

Debo: 

Wow, all right. That is very challenging actually to explain in a simple way. But to me, quantum is basically the truth to the universe. It is the laws on which our world works. Quantum physics tells us that everything is particles and waves. They behave like different things in different regimes. But truly, we can describe everything using wave functions. And that means that we have properties like superposition and entanglement and interference that govern everyday things that we see. 

Andrew: 

I think another way to think about it is quantum comes from the word quantized, which you can think about that as discrete as countable. So what they discovered in the last century was that if you divide reality, if you keep going into smaller and smaller parts, eventually you reach a limit where you can’t divide a system any further, you reach an indivisible part. 

And once you’re at that limit, you have to think about things in terms of individual quantum quantities, in terms of their individual discrete energy levels, discrete components, discrete particles. 

We’re so much larger than the size of an atom. So when we can kind of think about things in terms of their aggregate, we don’t need to worry about the individual atom, the individual electron. 

We just need to look at their bulk behavior. So those quantum effects don’t really affect us, don’t really we don’t really see those quantum effects in the macroscopic world because they’re they kind of get hidden by the mass of all of them happening in parallel. 

Miranda: 

So, simply, what’s a quantum computer? 

Andrew: 

A quantum computer utilizes a quantum state for its fundamental processing unit. So a qubit is similar to a bit in that it can be in a state zero and a state one. But because of the quantum properties of superposition and entanglement, you end up with this larger state space. Now the interesting thing is when you measure the qubits, when you measure the system at the end, you can only project it to one of the axes. That’s the way I like to think about that, is imagine if you had a flashlight that you were pointing at the ball along the equator and the shadow that the that the vector places that the vector projects on to the north and south axis, the shadow that puts along the axis is the probability of it being in one state versus the other. 

So if I have the vector pointing all the way up, the shadow is going to be pointing all the way up. It’s 100% probability of it being up. But if my vector is pointing along the equator and I shine this light in along the equator, now it’s going to project to a point right in the middle of the ball, and that’s going to give 50% probability of being up, 50% being down. 

So you can imagine then how if that vector is pointing anywhere else in the ball, you could end up with different projections. 

Miranda: 

So this is my thesis statement about this whole episode—is that what you’ve just told us is about probability. And the word quantum, and the idea of quantum computing in pop culture, has become kind of a code word or a narrative shortcut for infinite possibility. So I want to talk about that, how that’s portrayed in Marvel with the Ant-Man series. 

What did they get right? What did they get wrong? What does a quantum realm look like, really? 

Andrew: 

What we think of as what does something look like is what, what does how does light interact with that and how does light interact with that device and reflect off of it? Go into our retina so that we can see it. 

But if you’re the size of a light particle, how do you see a photon? How do you see an electron if the electron is smaller than the photon? So vision really doesn’t it doesn’t really have any any sensible, any tangible reality. So it would really it would look dark. You wouldn’t see anything assuming we’d be able to function at that scale in any case. 

You wouldn’t be able to see the light reflecting off of anything because you would be smaller than the light. 

Debo: 

Let me try to offer a different interpretation or a different way. I see how we could take this. Let’s imagine if I were in the quantum realm, First of all, I see things through my eyes and I have eyes that are a certain size and they have receptors that can see light. Now, in order to shrink to the quantum realm, maybe I would have to shrink down to like an atom or a few atoms. 

Let’s say I still have a consciousness, even though I’m just a few atoms. And now we know that light is a certain color because it has a certain frequency or a certain wavelength. And we know that in quantum physics everything has a certain wave function. 

So they also have wave-like properties. Now, if I were just one atom, I would automatically be a wave, and everything surrounding me would also have their own wave function. So I think in that sense I would be more in tune and be able to sense things, not the way we sense things here now, but our wave functions would be interacting all the time with other wave functions, which means that instead of seeing colors, we would maybe be sensing or feeling colors all the time because we are sensing, we are always interacting with each other as wave functions. 

Andrew: 

I think one thing that a couple of things that Ant-Man kind of gets wrong is, one, there’s a lot of, of physical, tangible objects like they’re walking around on a planet or a base in the quantum realm interacting with other people, other inhabitants, kind of in the same sense of light. 

If you’re smaller than any matter, then you don’t have any anything to hold on to. So all of our every thing that we touch is mediated by electromagnetic forces, and that’s taken kind of in bulk in aggregate. So you’re, you’re interacting with all of the atoms in any table or glass that you would touch. But if you’re on the same size as the atoms, you would basically just fall through the cracks or you’d be pushed around ping pong back and forth between all these atoms, and you wouldn’t really be able to touch anything. 

There wouldn’t be anything small enough and dense enough that you could actually grab onto it. 

Debo: 

In terms of what they get right, it is the technical terms themselves. In terms of what they get wrong, is all of the context—

Andrew 

Everything else they get wrong. 

Debo: 

And it’s not something that I can be mad about because they still make entertaining movies that are really fun to watch, and so far I just think of Marvel movies as that. They’re entertaining and they are not true to the science, but I think what they help is popularize some of these terms, which means that when I talk to a friend, they’ll be, ‘Yes, are you talking about like Quantum, like an Ant-Man?’ And that helps me latch on to some of the words that they may already be familiar with instead of convincing them that they need to care about quantum entanglement. Because Marvel’s already used that in an incorrect context. 

Miranda: 

Where do they use quantum entanglement in that movie series? 

Debo: 

So I think they’ve there’s actually this really funny conversation in the second Ant-Man movie, Ant-Man and the Wasp, I think, where Scott Lang and go visit this professor who they pull aside and he just mentions quantum entanglement. He’s like, yes, yes, yes, this, this is quantum entanglement. And Scott Lang’s like, ‘Do you add quantum in front of everything?’ 

So they’re kind of poking fun at themselves. 

They used the word quantum entanglement to mean like things are correlated, which is the real definition in quantum physics that states or functions are correlated. If you have two particles and you can describe them using wave functions, which means that they are in complex superpositions, but their states are correlated. 

It’s just when they use it, they’re talking about like these huge entities being entangled in weird ways. That’s not something that we’ve seen in nature so far. 

Andrew: 

And I think with all science fiction, you kind of need to hold the science with a huge grain of salt, right? I think too, on other franchises, like what is a flux capacitor or a positronic net? Like, we don’t actually have those devices and the physics behind a lot of the premises of science fiction is not based in what in physical reality, but it’s also not meant to be based in physical reality. Right? The point of the point is to introduce an interesting plot element and interesting narrative tool that they can explore. So I don’t have a problem with the quantum realm or anything like that. From a narrative perspective, I think it makes a really interesting, compelling story to have this place where you can access different realities and it’s kind of separate from our universe, but still kind of connected. 

The issue is, is if people see that and assume that is gospel of quantum mechanics or take that too seriously and miss out on the beautiful reality of what quantum mechanics actually does tell us. 

Miranda: 

We know that Christopher Nolan has people who he talks to when he is making movies to be, to adhere more closely to the laws of physics or to consider them more carefully. So as sci-fi fans, both of you, how do you feel about Christopher Nolan’s movies, as opposed to Marvel? 

Andrew 

Yeah, so I think he does a better job of keeping it closer to more of a hard science fiction than the softer science fiction of Marvel, where the universe feels very much the same as our own world. 

But maybe one one physical law is different, or one you need to suspend your disbelief on this. Grant me this one thing. And here’s a here’s a story, too, that kind of elaborates and takes that to, to a further extreme. So I really like that. It seems a lot more consistent. So one movie that I always go back to is Interstellar. Like, we don’t have faster-than-light travel at this point, but if we did, if we did have the ability to travel to a world that’s orbiting a black hole, like he gets the time dilation pretty accurate. 

Debo: 

They consulted very closely Kip Thorne, who was behind the gravitational wave detection breakthrough that won a Nobel Prize. The rules of the movie feel much more grounded. And when they do break a few rules, given our current understanding of physics, it feels a lot more believable. 

It’s a great story. It’s built on believable rules and they’ve Christopher Nolan just developed the characters, right? You really get behind each of the characters and that’s why I love the movie. 

Andrew: 

I don’t think science fiction needs to be 100% accurate to be, to make for an interesting story or to even be believable. Because if you wanted to write science fiction exactly like our current world, it wouldn’t be science fiction. Right? You have to suspend some disbelief, stretch things a bit beyond what we have or what we can achieve right now in order to build this believable premise. 

But I think the interesting thing is you have the spectrum where some some movies, some some shows take that where just throw ‘quantum’ in front of it and call it a day or just throw a scientific buzzword, pair a scientific buzz word with something we currently know—a flux capacitor. Put those two together and now it’s a mad multiverse, multiverse, time travel, whatever. 

And now it’s a magical MacGuffin that we can use to fulfill any plot point, deus ex machina, that we could want. 

I think nowadays, quantum is used just as a stand in for flashy, new, modern, unknown. Even like you saw this just in the last season of Black Mirror, where they use a quantum computer for this this one episode, “Joan is Awful,” as a device which was able to compute and process multiple different realities. And the show focuses more on artificial intelligence—like the point is more about artificial intelligence, intellectual property, and like computer-generated images, art and things like that. 

And the quantum computer is kind of just stuck in there as as that device to make that possible. But there’s nothing quantum about that quantum computer. 

Debo: 

Yes. 

Miranda: 

The producer, I forget her name, but she was like, ‘This is a quantum computer, right? We barely know how it works. It’s basically magic.’ You know, it’s like, that’s exactly—

Debo: 

Not true.  

Miranda: 

Not true, and that’s exactly how the word quantum is used. You know, it’s shortcut for magic. 

Debo: 

One of the funniest to me is this ad for like mechanics, like, ‘You don’t need to go to school. Come to our school for the quantum mechanic.’ I think that’s really funny because I practice quantum mechanics. Am I a quantum mechanic? 

Miranda: 

I don’t know. Are you? 

Debo: 

And the poster has a picture of a guy with a wrench in his hand. 

Andrew: 

There’s a quantum laundry detergent, and I saw a quantum whiskey distiller. It’s just a fun buzzword that makes it seem more modern and edgy even though there’s nothing quantum.  

Miranda: 

Quantum whiskey. I mean … 

Debo: 

So we’ve already talked about Christopher Nolan, Christopher Nolan’s movies, which are grounded in rules of physics. And then there is movies that are far on the fantasy side. So Marvel movies, Ant-Man and Jonah’s awful is this uncanny valley between these two bodies to me, because it has believable rules, because the show in general points out the horrors of sci fi and. It starts off on this believable story of this person, who is kind of just a an average person. 

But the the things that she did in her life, are pointed out in such a negative tone in the show, and that is a realizable horror that could come from advanced A.I., maybe, maybe from quantum computing, too, but not in the way that the I would say not in the way that Black Mirror depicts it to. 

And there are these realizable horrors that can come, which is why Black Mirror, when Black Mirror puts a show out to me, the implications are a lot bigger than, for example, Marvel, because you know that this could come true. 

Andrew: 

Yeah, no one’s really taking Marvel as seriously. You’re expected to take it with a pinch of salt, right? 

Miranda: 

It’s like I think that is the thing about one of the things about that episode, “Joan is Awful,” that’s so interesting to me is that it’s instilling this idea that quantum computing in the, you know, now we’re not too distant future has these capabilities that can tailor, you know, unique entertainment to the individual user, which is not like at all, you know, what’s going on in real quantum R&D, right? 

So like, what kind of things is quantum computing able to achieve right now? And what what might it be able to do in the next few years? What’s the actual level of investment that the public should have in technology? 

Debo: 

So quantum computers are really good at simulating the quantum physical laws that govern things in physics that kind of baffle physicists, for example, manybody physics, there’s a lot of problems that we don’t know the best way to model on classical computers because that just doesn’t work. Classical computers suck at simulating certain things. 

Miranda: 

What kind of things? 

Debo: 

Things where the runtime can grow exponentially with the complexity of the problem. So for example, simulating how a protein would fold and interact with certain bio biomolecules in your body. This is why we think quantum computers might be useful at simulating that and maybe even accelerating drug discovery. But that is still far out. 

I think the most useful near-term application is studying quantum physics and maybe optimizing certain things with supply chains, for example, maybe solve optimizing certain problems that are similar to the traveling salesman problem. 

Miranda: 

What is the traveling salesman problem? 

Debo: 

So traveling salesman problem is this problem where if you have to deliver, for example, n things to n cities, what’s the shortest, most efficient path that you can take? And this might sound like a simple problem. Let’s say you have 20 cities in the US and you have to just find the shortest path that will save you the most fuel. 

So these are the kind of problems that we think quantum computers may be able to solve more efficiently. But when it comes to, for example, “Joan is Awful,” they do paint a picture of quantum computers as being able to simulate multiple realities or like it just does everything and it’s kind of magic, whereas my quantum computer is my quantum computer in the lab is the opposite of magic. It is something that I need to build. It is something that I understand very well. Quantum computers are things we understand exactly. And we know how they manipulate these superpositions to give us the right answer at the end because. We have to design those algorithms for the quantum computer to operate them on. 

Andrew: 

I think one of the most common traps that people run into when thinking about quantum algorithms is a lot of people in pop culture say, you can create these superpositions so you can calculate every possible computation at once. So if I have, you know, 20 different calculations, I need to run in parallel. I can just create a superposition of all 20 of them and run all those possibles or the traveling salesman problem. 

I can simulate all the possibilities of the traveling salesman problem at the same time, and that is absolutely not the case. So quantum computers have specific advantages for certain algorithms. It’s an algorithmic speed up, not a parallelization. And I think if you wanted to make a science fiction about near term or quantum computing, as far as we know, it wouldn’t look it wouldn’t look all that interesting. It wouldn’t be as entertaining and it might even be a little more focused, more heavily on public policy and sociology and and things like that, as opposed to just a fun sci-fi concept. 

So, portfolio optimization or logistics optimization, the fundamental premise would, now Amazon can do things, you know, 5% more efficiently or now maybe this another option would be portfolio optimization. So if we can develop an algorithm that can optimize your investment portfolio to maximize returns, well, what if the the, the large head hedge funds, the large groups on Wall Street, they have access to these quantum resources and are able to optimize their portfolios more efficiently, whereas the average user, you and I wouldn’t have access to these computers because of the cost required to develop and run them and the limited and the scarcity of the resource. 

So there’s a social implication. There is like, ‘Does that create an unfair market platform, does that create unfair trading?’ But the fundamental premise doesn’t feel as science fiction-y. 

Debo: 

Yeah, I love that idea because exactly like you said, quantum computers are— quantum computing is an expensive endeavor. And there are certain countries, certain companies that have enough resources to be doing R&D in this field. So if we realize useful practical quantum computers, if and when we realize that, what does it mean for the people who are left out, for the nations that are left out? 

What for the other communities that are left out? What are the socio-economic implications? I think that would be an interesting movie to see. 

Miranda: 

That would be a great movie. Yes. The social justice aspect of quantum computing… 

Debo: 

Yeah. 

Miranda: 

Okay, so if there is one thing to take away from this episode, it is quantum computers are not magic, but you can learn more about them, how they work and what they’re capable of. By visiting quantum.duke.edu. You can also check out some of Debo’s physics explainers on YouTube by following the link in the show notes.