First quantum simulation of a wormhole opens a new door to understanding the universe | Science

Animation of the black hole Cygnus X-1.NASA/CXC/M.Weiss

Quantum mechanics and the theory of relativity are like Cain and Abel, two mismatched children of the same nature, but one focuses on matter at subatomic scales, while the other is connected to the macroscopic world. Both theories are incompatible, so finding a compromise point is crucial to understanding physical reality. A step in that direction has been taken with the first quantum simulation of the wormhole, performed with the Google Sycamore processor, released this Wednesday. Nature. According to Maria Spiropulo, a physicist at the California Institute of Technology (Caltech) and one of the study’s authors, with this experiment, “it was observed that the properties of a quantum system match those expected in a gravitational system.” An exploration that allows progress. A new door to understanding the universe.

A worm holeAlso known as the Einstein-Rosen bridge, it is a shortcut in space and time, as if there were a shortcut between two galaxies light-years away. As theoretically shown, this shortcut can be created when two entangled black holes are created. The wormhole is similar to two funnels joined by the smaller mouth and black holes at the more open ends.

However, contrary to what is projected in science fiction movies, this shortcut in space cannot be used alone to transmit information. The problem is that if any object or message is thrown through it, the hole never reaches the other end as it stretches and contracts. Actually, the object disappears in a central singularity, as usual when entering a black hole that does not let light through. But if a conventional interaction, transmitted at the speed of light, is established between two observers at the ends of the wormhole, the hole will open so that one can pass through it.

This phenomenon cannot be observed experimentally, as it is not possible to create two entangled black holes in a laboratory. However, it is possible to examine the “holographic equivalent” of this process, which is one of the achievements of the study published today.

Alberto Casas, CSIC Research Professor at the Institute for Theoretical Physics (CSIC-UAM) and author of the following book: quantum revolution (Edition B, 2022) simplifies for clarity. “It’s like a cylindrical box. There are three dimensions inside, but the ends are two-dimensional, straight. Everything that happens inside with gravity has a reflection or can be seen on non-gravity eyelids”. It’s what’s called the holographic principle, which is suspected to be fulfilled in a coherent theory of quantum gravity and, as Casas explains, “what happens in a theory with gravity is without it and the equivalent in a one-dimensional theory is minimal. Specifically, the wormhole in gravitational theory is a quantum entanglement in theory without it. And the transmission of information through the wormhole will be seen in non-gravity theory as a phenomenon similar to quantum teleportation.

This is essentially the study published this Wednesday. “The authors created an entangled system between two parts of a quantum computer, the holographic equivalent of which is a wormhole. And they confirmed that there is this kind of information transfer between these parts. quantum teleportationmimics exactly what would happen through the equivalent wormhole,” explains Casas.

Representation of a quantum simulated wormhole.
Representation of a quantum simulated wormhole.Nature

This phenomenon is striking because the message written by Alice [nombre utilizado en física cuántica para definir a un emisor] seems to be irretrievably lost in the first subsystem, but soon reappears entirely in Bob’s subsystem [el receptor del mensaje]. “It’s as if Alice wrote a message on the surface of the water. It would seem that trillions of water molecules would be lost in their movement, making it impossible to recover. But we can soon imagine the entire message reappearing at another spot on the liquid surface. This surprising behavior Occurs between two interconnected systems The startling phenomenon created in this experiment is a little clearer if we consider its holographic equivalent: the message written by Alice is swallowed by the wormhole and transmitted to the end where Bob is,” adds the author. quantum revolution.

“The achievements are very interesting because they were achieved with a more powerful computer,” adds Casas. [en la simulación solo se han utilizado nueve cúbits] macroscopic systems can be simulated and the effects of quantum gravity on them can be studied.”

published work Nature He acknowledges that the simulation can be done with traditional computing, but acknowledges that the use of Google Sycamore adds a fundamental element. In this sense, the California Institute of Technology emphasizes that the simulation, completed with the Google computer, “opens the possibility of performing quantum gravity experiments on processors based on this physics,” thus increasing the possibilities for studying this science and this computation.

The view of Ignacio Cirac, director of the Theory Department at the Max-Planck Institute for Quantum Optics in Garching (Germany), is the same. “Existing quantum computer prototypes, or those that will be built in the near future, could become an important tool for tackling fundamental questions. The experiment is still a very simple but important step. This kind of simulation is an insight into how black holes behave, especially when we study them from the perspective of quantum physics. can provide,” explains Cirac. Science Media Center (SMC).

Carlos Sabín, a Ramón y Cajal researcher in the Department of Theoretical Physics at the Autonomous University of Madrid (UAM), also thinks it’s important to understand that no wormholes were created in this experiment. “We’re talking about an analogy,” he describes. But he emphasizes that the experiment involves creating “a dictionary that translates into the language of what happens to a simulated or virtual qubit what happens to a real qubit.” “The authors,” adds Sabín, to the SMC, “offer techniques that show how the experiment can be extended efficiently to a higher number of qubits, so that when we have quantum computers an experiment can be performed beyond the capabilities of a conventional computer, with lower error probabilities expected in the coming years.” ” “At any rate,” the physicist concludes, “this experiment shows that even with a few qubits and error probabilities available, quantum computers can already do interesting things.”

Researchers at Google and Adam R. Brown and Leonard Susskind of the Department of Theoretical Physics at Stanford University (California) Nature The relevance of simulation of the holographic principle as “a guide for combining quantum mechanics with general relativity” has been a direction sought for decades to find a theory that allows us to understand nature. They also emphasize the importance of information transfer: “In the non-gravity description, the unencoded message appearing elsewhere is a precise prediction of quantum mechanics, but somewhat mysterious. The surprise is not that the message somehow arrives, but that it arrives undeciphered. However, this is easily from the gravity definition. understandable: the message reaches the other party undecrypted, as it passes through the wormhole.

“In the future, we can expect quantum communication techniques to be invented that are very difficult to analyze using conventional methods, but that use holographic duality as a powerful analysis and discovery tool.”

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