The first quantum simulation of a wormhole opens a new door to understand the universe

The research manages to transmit information through this shortcut in space-time, which represents an advance in the understanding of quantum gravity.

Quantum mechanics and the theory of relativity are like Cain and Abel, two mismatched children of the same nature, but one focused on matter at subatomic scales and the other linked to the macroscopic world. Both theories are incompatible, so finding a point of reconciliation is essential to understand physical reality. A step in this direction has been taken with the first quantum simulation of a wormhole carried out with the Google Sycamore processor, as published by Nature. With this experiment it has been observed, according to Maria Spiropulo, a physicist at the California Institute of Technology (Caltech) and one of the authors of the work, “that the properties of a quantum system coincide with what is expected in a gravitational system”, a discovery that allows progress in the study of black holes and the hypothesis of quantum gravity in the laboratory using computers based on this mechanics. A new door to understand the universe.

A wormhole, also known as an Einstein-Rosen bridge, is a shortcut through space and time, as if there was a short path between two galaxies light-years away. As has been shown theoretically, this shortcut can be generated when two entangled black holes are created. The wormhole would be similar to two funnels joined by the smaller mouth and with the black holes at the more open ends. However, contrary to what is reflected in science fiction movies, this shortcut in space cannot be used by itself to transmit information. The problem is that if any object or message is thrown through it, it never reaches the other end, as the hole stretches and narrows. In fact, the object ends up destroyed in a central singularity, as is usual when entering a black hole, which does not let even light through. However, if a conventional interaction (transmitted at the speed of light) is established between two observers located at the ends of the wormhole, the hole opens in such a way that it can be traversed.

This phenomenon cannot be observed experimentally, since it is not feasible to create two entangled black holes in a laboratory. However, it is possible to study the “holographic equivalent” of this process.

Alberto Casas, CSIC Research Professor at the Institute of Theoretical Physics (CSIC-UAM) and author of The Quantum Revolution (Ediciones B, 2022), simplifies it to make it understandable. “It’s like a cylindrical can. Inside there are three dimensions, but the ends are two-dimensional, flat. Everything that happens inside, with gravity, has a reflection or can be seen on the lids, where there is no gravity”. It is what is called the holographic principle, which is suspected to be fulfilled in a theory of consistent quantum gravity and by which, as Casas explains, “what happens in a theory with gravity has an equivalent in a theory without it and with one dimension less. Specifically, the wormhole in the theory with gravity would be seen as a quantum entangled system in the theory without it. And the transmission of information through the wormhole would be seen as a phenomenon similar to quantum teleportation in the theory without gravity.

The phenomenon is very striking, since the message written by Alice [name used in quantum physics to define a sender] seems to be irremediably lost within the first subsystem, but shortly after it reappears in its entirety in Bob’s subsystem [the receiver of the message]. “It’s like Alice wrote a message on the surface of the water. Apparently, it would be lost in the movements of trillions of water molecules, making it impossible to recover. However, we can imagine that, shortly after, the message reappears in its entirety at another point on the liquid surface. This surprising behavior is what actually happens between the two entangled systems that have been created in this experiment. The amazing phenomenon is somewhat more understandable if we think of its holographic equivalent: the message written by Alice is swallowed by the wormhole and delivered to the end where Bob is”, adds the author of The Quantum Revolution.