Looking for quantum gravity Learn about quantum computers

An arXiv paper on May 30, "Making Quantum Gravity in a Quantum Processor Lab" [1] shows that the Lawrence Berkeley National Laboratory team's use of holographic principles and their implementation in the AdS/CFT correspondence led to The connection between general relativity and quantum information lays the foundation for studying various aspects of quantum gravity models.

One of the great challenges of science is how to reconcile the two theories that underlie modern physics—quantum field theory and general relativity: the former governs the universe on the smallest scales, the latter on the largest scales. Together, these two theories accurately describe phenomena over 40 orders of magnitude.

What puzzles researchers is: what happens where these theories overlap? In other words, how does gravity behave on a quantum scale? Although physicists have yet to simulate quantum gravity itself, the simulations have revealed a new phenomenon: a way of perfectly transporting classical information from chaotic quantum systems.

"This is a surprising result, since one would not expect an imposed scrambling system to transmit classical bits," said Illya Shapoval and colleagues at Lawrence Berkeley National Laboratory in California. The new approach to gravity has been extremely fruitful, they add: "The process of developing a practical experimental protocol itself has led to new theoretical insights into quantum dynamics."

The team's approach builds on the latest theoretical advance in quantum gravity -- the principle of holography, which states that the three-dimensional reality we see around us is a hologram encoded on a two-dimensional surface. Through this theory, gravity emerges from a two-dimensional representation in a connection between conformal field theory (CFT) and general relativity in Anti-de Sitter space (AdS).

Physicists call this the AdS/CFT correspondence, and it's their current best guess at the nature of quantum gravity. However, the theory's potential test predictions are extremely subtle and small-scale, and no one has been able to find a way to observe them, because the AdS/CFT theory only works in universes that are significantly different from the one we live in. But physicists have found a few avenues that promise to take the theory further: One is to study how quantum information flows between two black holes. It has been shown that under extreme conditions, it is possible to transmit quantum information from one black hole to another, similar to the way information travels between them through a wormhole.

Circuit overview of the wormhole-inspired teleportation (WIT) protocol. The key steps are the preparation of Bell pairs (blue), the temporal evolution of forward (green) and backward (red), and two-sided coupling (orange). The successful teleportation of the state |ψ⟩ can be judged by studying the correlations of time evolution operators.

This "wormhole-inspired teleportation" process can be tested in certain ways in our own universe, and the test results can shed new light on the AdS/CFT correspondence and the nature of quantum gravity, which is Shapoval The significance of the findings of et al. While it is impossible to observe the phenomenon directly, "it may be possible to probe quantum gravity indirectly in the laboratory using quantum simulators and quantum computers".

In the experiment, they used two types of quantum computers: the first is the IBM Quantum, a quantum computer with seven superconducting transmon qubits; the second is the Quantinuum ion trap quantum processor, which can process up to six qubits .

At the same time, the team also developed quantum software to reproduce wormhole-inspired teleportation on two quantum computers. As a result, they were able to transmit a classical bit perfectly, although the same system would scramble the quantum information. "We designed and performed wormhole-inspired many-body teleportation experiments on IBM and Quantinuum quantum processors, and finally observed signals consistent with predictions," Shapoval said. "Our findings suggest a potential mechanism for AdS/CFT. The new problem is that in these mechanisms, traversable wormholes can transmit classical data rather than quantum data."

This is just the beginning.

Why this happens is still unclear. At the same time, does this mechanism offer any advantage in transmitting information in this way? "The larger conclusion is that the process of developing a practical experimental protocol itself has led to new theoretical insights into quantum dynamics," said the research team. "We conclude that this work has likely reached a point where there are Important qualitative and quantitative results may be obtained from even more advanced experiments in this direction." While this method cannot directly measure quantum gravity, it should help physicists explore experimental and theoretical frameworks that may reveal it in the future.

The work has far-reaching implications: it may eventually provide testable evidence for quantum gravity and provide a way to combine quantum field theory and general relativity; even if not, the new ways of thinking about information it allows for Physicists offer a great deal of thought.

Link:

[1] https://arxiv.org/abs/2205.14081

[2] https://www.discovermagazine.com/the-sciences/quantum-computers-are-physicists-latest-tools-for-discovering-quantum