Recent Nature The publication continues to generate headlines for its findings that Caltech scientists have developed a model of a wormhole that can be passed through in the Google Sycamore quantum processing system.
Penn Today spoke with physicists Vijay Balasubramanian and Jonathan Heckman from the Department of Physics and Astronomy at the College of Arts and Sciences to better understand the implications of the study. The two explained some key concepts and shared their thoughts and opinions on some of the key points.
Can you explain what these researchers did?
Balasubramanian: These Caltech researchers were able to represent a wormhole-like state in their quantum computer.
They used quantum computers to build a simple version of a model often used to understand strongly correlated materials, materials whose underlying components strongly influence how they behave with each other. This is the so-called SYK model, named after the condensed matter physicists who originally proposed it, Subir Sachdev and Jinwu Ye, and later modified it, Alexei Kitaev.
Famously, this SYK model gives an equivalent explanation for a particular gravitational theory of the universe, which has only one spatial dimension.in the Nature In the paper, the researchers constructed a quantum system that realized a simplified version of the SYK model and demonstrated the characteristic dynamics associated with traversable wormholes in alternative equivalent gravitational descriptions.
Aren’t they making real wormholes?
Balasubramanian: No, they haven’t created a wormhole or a shortcut connection between two distant points in space. and a big step forward for quantum computing.
What does quantum computing mean, and why was quantum computing necessary for this experiment?
Heckman: In contrast to ordinary computer systems, which use binary bits corresponding to 0s and 1s to receive, process, store, and communicate information, quantum systems have a “superposition” of 0s and 1s. . A qubit can exist as 0 or 1 at the same time.
So the hope and promise of quantum computers is that given enough qubits, they can perform computations that conventional computers cannot.
My understanding is that these researchers were motivated by what is known as the anti-de Sitter/conformal field theory (AdS/CFT) correspondence. This, like the SYK model, is useful for studying phenomena in systems in which components strongly interact with each other. However, the AdS/CFT correspondence is particularly useful for studying equivalence between two different types of physical theories.
Balasubramanian: AdS/CFT communication can be compared to expressing an idea in one language and using dictionaries and grammar books to convey the same idea with an entirely different set of sounds and grammatical practices associated with another language. I can do it.
In a little more detail, the AdS/CFT correspondence provides a dictionary and set of physical rules for translating phenomena in a particular kind of high-dimensional gravitational universe (the so-called anti-De Sitter space) into phenomena in other low-dimensional systems. (the so-called conformal field theory, which does not experience gravity). This correspondence is actually rooted in a notion established in physics dating back to the late nineteenth century, which we call duality, but the new incarnation of duality is the most recent in physics of the last quarter. One of the key discoveries. century.
That theories of different dimensionality can be equivalent seems incredible, perhaps impossible, at first. After all, you would think that dimensions are kind of fundamental to the nature of physics. Usually, the dimension of space feels like a stage, you can move forward, backward, left, right, up and down. It takes place in a three-dimensional theory that does not include gravity, and can be shown to be equivalent to other processes in a four-dimensional theory with gravity.
Heckman: Based on that, Caltech researchers hoped that quantum processors could be used to teleport or transform quantum information from one domain to another without losing signal fidelity. rice field. Via the AdS/CFT duality, we can say that for an equivalent gravitational description with the extra dimension, the signal has passed through a wormhole. But the actual machine they used doesn’t have one.
In fact, there is a version of this Nature paper that does not mention quantum gravity or the AdS/CFT model at all.
Why? Doesn’t that negate the point of studying wormhole-like environments to analyze information?
Heckman: Basically, the idea here is that gravity encodes information via a kind of hologram. A real hologram can use a two-dimensional system (such as an image etched into its surface) that can be used to perfectly encode the original three-dimensional shape. Similarly, the AdS/CFT duality encodes information in a high-dimensional gravitational system into a low-dimensional system.
But in terms of what they did, some special considerations about gravity, in particular motivating the experiment based on this idea of the wormhole configuration of gravity, are tricky here. To create a wormhole, you need to build a bridge between two black holes. The black hole in question does not exist in our world. Rather, they exist in another “dual” description of their quantum computing system in terms of gravitational theories in different numbers of dimensions.
So, in a way, they used this “dual” concept of gravity to imagine a passable bridge, or wormhole, connecting two different quantum mechanical systems, and build this on a quantum computer. I converted it to the equivalent phenomenon of the actual system I made.
Much of the media coverage of this Nature The paper suggests that researchers have created a wormhole. What are your thoughts on these claims?
Heckman: To imply that wormhole traversals are actually happening in our world is pretty misleading. The author of the article and the news outlets covering it are engaged in a highly irresponsible presentation of the work.
This particular gravity model works best when the number of qubits is very large, such as approaching infinity, which is currently not possible. As such, researchers address this by using deep learning networks to build sufficiently small quanta. A system that retains sufficient gravitational properties to operate in a nine-qubit system and still holds true. In this case, are we going to learn anything about quantum gravity from the Sycamore system?
So, a priori, I could have done the whole experiment without saying anything about AdS/CFT support or links to wormholes. In fact, the entire experiment could have been run on a conventional machine. It would have taken longer.
Balasubramanian: It’s similar to Pixar’s version of the wormhole in that it’s a lab-made wormhole, but it’s not what you see on screen. It’s more like raw code running in the background. It’s not converted to a readable image, but theoretically it is possible. This image may look like a traversable wormhole, but it is not.
Again, they’re not building wormholes in our world. It takes a mental gymnastics to say they did. Basically, the “double” description of gravity in those systems should be considered real-world.
In any case, they produced fascinating quantum phenomena in systems that are very difficult to simulate with computers. This is a step towards simulating complex interacting systems with quantum computers, and what is interesting is that one of the most useful applications of quantum computing is to study physics such as protein folding in living cells. This is because it simulates the interaction of This is very difficult to do on a normal machine, so there is a drive to improve this technology beyond just gathering insights into theoretical physics models.
For more information:
Daniel Jafferis et al., Dynamics of traversable wormholes in quantum processors, Nature (2022). DOI: 10.1038/s41586-022-05424-3
Courtesy of the University of Pennsylvania
Quote: The researchers used a recent quantum computer wormhole model (22 Dec 2022 ) will be discussed.
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