How Physicists Created a Holographic Wormhole in a Quantum Computer

Nobody has seen a wormhole. Nobody has produced one. Nobody knows if it is just beautiful  math, but without a physical reality. Well, we'll take the world's best quantum computer   and see if we can map that  into building a wormhole. And then it became just at  the edge of what's possible. I think the discovery of the Higgs, which  came about 10 years ago, was up to that   point the most exciting point of my entire  career. This, to me, is equally exciting. It can begin to explore quantum states that  are very hard to realize in nature directly. Now, the wormhole becomes traversable.  It opens. You really can go through. So, the story begins in 1935 when Einstein wrote   a paper with Rosen, where the first  time Einstein-Rosen bridges appear. And these are bridges that connect two  seemingly unconnectable pieces of space-time. ER–Einstein and Rosen–they pointed out that  solutions to general relativity allowed for two   black holes, which are connected, but with  a kind of bridge–what we call a wormhole. But that wormhole has the  property of being non-traversable. Wormhole is a very unstable passage. It opens and it closes and it gets  chaotic and it gets destroyed very fast. So Einstein, when he proposed the  wormhole, he was very frustrated,   because you couldn't actually go through a  wormhole. And he was able to realize that   himself. And so, what good is a wormhole  if you can't put anything through it?   And it turns out that that's because he  wasn't putting in the quantum physics. 1935: same year, another paper. The EPR paper, which is Einstein, Rosen, Podolsky. EPR is about quantum entanglement and what  Einstein called spooky action at a distance,   something he was not happy with. Entanglement is this property when subatomic  particles–they are partners. Even if you take   them apart, and take them at the other edge of  the universe, they hold information that if you   measure the one, you know what the other will  be. So entanglement is a strong correlation. Einstein didn't like quantum entanglement,  and this made it very challenging for him   to understand how to reconcile quantum  physics and gravitational physics. So it   has been a challenge over decades  to understand better how quantum   physics and general relativity fit  together into a coherent picture. Einstein's dream was to figure  out how to connect them. There was no reason to think at the time or  for decades afterward that those two papers had   anything to do with one another, apart  from there being some authors in common. And then comes 2013: Maldecena and  Lenny Susskind. They say ER equals EPR. They are the same. This is very daring. Wormholes and entanglement are the same thing.   That was totally unexpected. One of them  has to do with black holes. One of them   has to do with quantum mechanics. Didn't seem  like they had anything to do with each other. A lot of times in physics, you can have  two different descriptions of the same   thing. And we call that a duality. It's just  sort of a remapping of the same physics. The basic idea was that when you  have quantum entanglement between   two black holes, necessarily there  will be a wormhole connecting them. So there we have a picture of quantum gravity. We have this dictionary that relates gravitational  phenomena to ordinary quantum physics. You can tackle the same physics from these  two different angles, and that's one of the   most concrete paths forward we have in  building a full theory of quantum gravity. The physics of the black holes, we think,  is physics of quantum gravity. But we cannot   send an experiment in a  black hole and validate that. So instead we can ask, can  there be quantum systems   whose dual description looks like space-time? I think it might have actually been during a talk   by Juan Maldacena about ER = EPR  that I started to wonder to myself:  Could traversable wormholes exist? And people  thought it was fascinating as an exotic   configuration of space-time. But I think many  people probably suspected that it couldn't work. So we saw that it could. One of the magical things about quantum  mechanics is you can actually have negative   energy. And this allows you to do things that  you would've thought otherwise were impossible. Daniel Jafferis showed was that if you introduce  what’s known as a negative energy shockwave,   you can support your wormhole and get something  from one end and have it come out the other. Now, I'm an experimentalist, so I look at that  and I ... All right, what can I do about that? And so Maria and I were thinking, we have  the ability to do things in quantum in   the laboratory. We're physicists. So could we  imagine actually doing something with wormholes? It almost occurred to us immediately that  we should be using the best quantum system   that we know how to manipulate. And  what is that? It's a quantum computer. Quantum computers speak a different  language than the ordinary language of   bits. A bit–you look at it, okay,  it's a zero or one, that's it. The correlations among qubits are richer  and a lot more interesting than correlations   among bits. It’s this language of quantum  entanglement. And so there's a world out there,   this extravagant quantum world, which  we just haven't been able to explore. I've worked on a few projects at Google Quantum,  and got to get to know the device a bit. The Google device is the best  quantum computer that is around. All the magic happens in this little chip. You  have the actual qubits as these superconducting   pieces of aluminum on a silicon chip. And  that's where the entanglement happens. We had access to the Google quantum  computer. And so Maria and Daniel and   Joe and I said, “We have a proposal to try to  observe a wormhole on the quantum computer." And to put the proposal together, it  was obvious that these are the people. In physics, you have to have the courage of  your own convictions. And you say, "Well,   maybe it won't work the way that I thought,  but we'll learn something by trying." And   that's really the attitude we had going  into this. I don't think we really thought   it was going to work, but we thought we would  learn a lot by seeing how far you could get. They didn't say, "You're crazy.  Let's do something else."   They said, "Okay, you are crazy. Let's do it." You can use the holographic duality to  create the quantum version of the system. We look instead at this set of  entangled qubits and we evolve   it in a way that has exactly the same  physics as the gravitational wormhole. And so, on the quantum computer,  we can directly send a qubit from   one side of the wormhole and  watch it come out the other. If you take the physical system that theoretical  physicists say, "this is a wormhole," and you   work out pencil-and-paper, "how good of  a quantum computer do I need?" You get an   answer that's like, "a quantum computer  10 years from now." It looks hopeless. But we thought, “Let's try.” We are here in our GQ2 lab… the controlled signals   actually are produced in these  racks sitting next to the cryostat. When you try to just run a wormhole  as the theorists have prepared it   on a quantum computer, you find that you  need to implement this very large system. So that's big. That's a big fat problem. We have to do what physicists  call coarse-graining. You want   to preserve certain features–in this case,   gravitational features, while throwing  away all the unnecessary components. We knew we needed to get to a smaller system size   and so we were banging our heads  against it for a year or something. And then finally, you come up  with a weird idea that might work. The idea of rewriting it as a neural network  is something that's out there. It's a weird   idea because you usually don't think of  physical wormholes as neural networks. The wormhole itself has these many  parameters that we treat as neural   network weights. We then have a data  set that we're going to train on,   which is the dynamics that we want to  observe that correspond to wormhole. It sounds like a generic  machine-learning problem now,   and we can just plug it straight  into the machine-learning toolbox. I proposed the idea and tried it out. The original system has 210 terms. And we found out that we can do this with seven. The machine learning managed to keep all of  this intact while making a much smaller system. It’s still baby enough that it fits in the crib. That was the first moment where,  like, "It might be possible. This   whole wormhole thing we've been talking about  for two years, maybe we can actually do it." At probably like two in the morning,  I was running these quantum circuits.   We're looking for a peak. That's the  qubit making it through the wormhole. I'm watching the data as it comes out and  there's a little bit of a noisy peak. And at   first I was like, this is probably just  a noise artifact. But as the data kept   coming in and the peak kept getting clearer  as it was like, “This is is a wormhole.” “I think I just saw one.” And so I was like  sending it off to Maria and the others,   like, “I think we have a wormhole, guys.” He said, "It's there." I  said, "No kidding it's there." It was nuts. It was nuts. The qubits of the Google quantum computer are   making a little bit of extra  space and that's our wormhole. What happens is, a pulse of negative  energy falls into the wormhole. Now, the wormhole becomes traversable. It opens. You put a qubit through one side of the wormhole. The qubit is now in the interior of this wormhole. That information will actually spread over  the entire quantum system over time. And   this spread of quantum information is chaotic. It becomes shared by many particles in the  form of very complicated quantum entanglement. After spreading, it has to  refocus onto a single qubit. As the wormhole is closing, the qubit is exiting. I was absolutely astounded. I thought we would get  maybe a few steps toward a real wormhole on a real   quantum computer. And I never really believed that  we'd get all the way to something that was real. The experimentalists have a reaction  like they want to hug the machine. I told my brother and he squealed and he  said, "Are you destroying the world? What   are you doing?" It was difficult to explain to  him that nobody is in danger from this wormhole. On the processor, if we had a  quantum eye and looked in there,   we wouldn't see a ripple of space-time. We would see the physics that we expect from   the gravity point of view and  from the quantum point of view. So if that is the case, then we are making  contact between quantum and gravity. That's been the holy grail of my whole  career–is to understand quantum gravity   and the things that go with it, like wormholes. We are studying quantum gravity  literally from the ground up. Einstein committed his life to arrive to  some understanding of quantum gravity, and   here we are almost a century later. I wish he was alive to see this because  I would like to know what he would say. What would have Einstein said? He would've said,  “ER = EPR. I told you. I knew that in 1935.”   But he didn't. I think this is concrete  experimental evidence for ER = EPR. The vector is pointing right from  the experimental point of view. This is a confirmation–a direct exploration–of  this connection between quantum entanglement   on the one hand and the way space is  knit together and holds itself together. As Google builds more and more capable  quantum computers, we will eventually   be able to get this into a regime where we don't  even know how to predict what's going to happen. And I think we're going to have  hundreds of my fellow physicists   now writing papers about all the  other things you can think about   doing now–now that we've sort of  got this door a little bit open. And as always in physics, when you  are able to explore a new frontier,   there will be discoveries that weren't  anticipated. Just like when you build a   more powerful accelerator to study particle  collisions or a more powerful telescope to   look at the more distant universe, a  more powerful quantum computer will be   able to study highly entangled matter that  we've never been able to look at before. Being very close with quantum,  we're going to learn a lot. There’s so many questions that one  could explore using these ideas.   And I think most exciting are the  questions that we can’t yet pose.

Channel: Quanta Magazine

Views: 1,648,421

Keywords: science, quanta, quanta magazine, explainer, science explainer, science video, educational video

Id: uOJCS1W1uzg

Length: 17min 4sec (1024 seconds)

Published: Wed Nov 30 2022

Reddit Comments

[u/kickff]

Might be the most AI-generated sounding title I've heard

[u/bonsainick]

I don't suppose anyone can do an ELI5 on this? Did they measure their qbits doing something interesting? Did they write a program on a fancy computer that solved a cool math problem?

[u/mala_cavilla]

Didn't they already do this with the game Portal?

[u/Nervous-Ear-8594]

I still can't understand how they did this with a computer. It's software, isn't it?

[u/g1immer0fh0pe]

A decade and more ago, I was often asked when I thought a real quantum computer would be built. (It is interesting that I no longer face this question as quantum-computing hype has apparently convinced people that these systems already exist or are just around the corner). My unequivocal answer was always that I do not know. Predicting the future of technology is impossible — it happens when it happens. One might try to draw an analogy with the past. It took the aviation industry more than 60 years to go from the Wright brothers to jumbo jets carrying hundreds of passengers thousands of miles. The immediate question is where quantum computing development, as it stands today, should be placed on that timeline. Is it with the Wright brothers in 1903? The first jet planes around 1940? Or maybe we’re still way back in the early 16th century, with Leonardo da Vinci’s flying machine? I do not know. Neither does anybody else.

-- Sankar Das Sarma; member of the Department of Physics at University of Maryland, College Park; in March, 2022 (source)

[u/spredditer]

Here's the paper: https://www.nature.com/articles/s41586-022-05424-3

[u/Pronage]

I want to watch this but the video editing and over dramatization just kills it for me.

[u/noobvin]

That this is just basically "data," I feel there is a huge asterix to this, but it's so over my head that I really don't know.

[u/kyotejones]

Anyone else think of the Mass Effect quantum communicator device? This is sorta like that lol.