Recently, a team of researchers from Google, Caltech, Harvard, MIT and Fermilab reported a remarkable achievement in this direction: they used Google's Sycamore quantum processor to create and manipulate a state that is equivalent to a traversable wormhole.
What is a wormhole?
A wormhole is a hypothetical shortcut in spacetime that connects two distant regions of the universe. The idea of a wormhole was first proposed by Albert Einstein and Nathan Rosen in 1935, when they studied black holes in the context of general relativity. They found that a black hole has two regions: an interior region, from which nothing can escape, and an exterior region, from where escape is still possible. The two regions are separated by a surface called the event horizon. However, they also discovered that there is actually another exterior region on the other side of the black hole, and that the two exterior regions are connected by a bridge-like structure, now known as an Einstein-Rosen bridge or a wormhole.
However, this wormhole is not traversable, meaning that one cannot travel from one exterior region to the other through it. Moreover, if someone jumps into the interior region of the black hole from one exterior region, they will inevitably meet their doom at the singularity, where the density and curvature of spacetime become infinite.
How to make a traversable wormhole?
In 2017, two physicists, Juan Maldacena and Leonard Susskind, proposed a way to make a wormhole traversable using quantum entanglement. Quantum entanglement is another phenomenon that Einstein and his collaborators discovered in 1935, when they studied quantum mechanics (without gravity). Quantum entanglement is a property of quantum systems that allows them to be linked through a strange, non-classical pattern of correlations, even when they are separated by extremely long distances. This pattern of correlations is a signature of quantum mechanics, because it cannot be reproduced by any classical process that doesn't involve faster-than-light communication.
Maldacena and Susskind showed that if two black holes are entangled with each other, then their wormholes become traversable. In other words, if someone sends a message into one black hole, it can come out from the other black hole without being destroyed by the singularity. This process is called wormhole teleportation.
How to simulate a wormhole on a quantum computer?
Simulating quantum gravity and wormholes on a quantum computer is extremely challenging, because we don't have a complete theory of quantum gravity yet. However, there is a powerful tool that can help us: the holographic principle. The holographic principle is a conjecture that states that theories that include both quantum mechanics and gravity can be exactly equivalent to other theories that involve quantum mechanics but not gravity. Such an alternative description is known as a dual, and has fewer dimensions than its gravitational counterpart — much like how a hologram projected on a 2D surface displays a 3D image.
One of the most famous examples of the holographic principle is the AdS/CFT correspondence, which establishes an equivalence between a theory that describes gravity and spacetime (and wormholes) in a fictional world with a special geometry (AdS) to a quantum theory that does not contain gravity at all (CFT). By studying this quantum theory on a quantum computer, we can leverage the AdS/CFT correspondence to probe the dynamics of a quantum system equivalent to a wormhole in a model of gravity.
This is exactly what the team of researchers did in their experiment. They used Google's Sycamore processor, which has 54 superconducting qubits (quantum bits), to simulate the CFT on nine qubits. They prepared an initial state that corresponds to two entangled black holes connected by a wormhole. Then they applied some operations on the qubits to mimic sending messages into one black hole and receiving them from the other black hole. They measured the qubits at different times to verify that their state indeed behaves like a traversable wormhole.
Why is this experiment important?
This experiment is important for several reasons. First, it demonstrates that quantum computers can be used to simulate quantum gravity and explore fundamental questions about the nature of spacetime and information. Second, it provides experimental evidence for the validity of the holographic principle and the AdS/CFT correspondence, which are still conjectural in many aspects. Third, it shows that wormhole teleportation is possible in principle, although it is still far from being feasible in practice.
The experiment also opens up new avenues for future research, such as simulating more realistic models of gravity and wormholes, testing the quantum information properties of black holes and wormholes, and investigating the connections between quantum entanglement, quantum error correction, and quantum gravity.
Conclusion
Google and its collaborators have created an artificial wormhole for quantum computer using the Sycamore processor. This is a remarkable achievement that showcases the power and potential of quantum computing for simulating quantum gravity and exploring fundamental physics. It also reveals the fascinating link between information and matter that has bedeviled physicis.
Source
(1) Making a Dual of a Traversable Wormhole with a Quantum Computer. https://ai.googleblog.com/2022/11/making-traversable-wormhole-with.html.
(2) A holographic wormhole traversed in a quantum computer - Nature. https://www.nature.com/articles/d41586-022-03832-z.
(3) Wormhole simulated in quantum computer could bolster theory that the .... https://www.livescience.com/physicists-create-holographic-wormhole.
(4) Google Researchers Create Traversable Holographic Wormhole Using ... - VICE. https://www.vice.com/en/article/bvmaaw/google-researchers-create-traversable-holographic-wormhole-using-quantum-computer-in-new-study.
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