A quantum computer simulated a wormhole for the first time

Researchers have used Google’s Sycamore quantum computer to simulate a simplified wormhole for the first time and sent quantum information through it

By Lea Crane

A quantum computer was used to simulate a holographic wormhole for the first time. In this case, the word “holographic” indicates a way to simplify physics problems involving both quantum mechanics and gravity, not a literal hologram, so simulations like this could help us figure out how to combine those two concepts in a theory of quantum gravity – perhaps the most difficult and important problem in physics at the moment.

Quantum mechanics, which governs the very small, and general relativity, which describes gravity and the very large, are enjoying extraordinary success in their respective fields, but these two fundamental theories do not go together. This incompatibility is particularly apparent in areas where both theories should apply, such as in and around black holes.

These areas are extraordinarily complicated, and this is where holography comes in. It allows physicists to create a less complex system that is equivalent to the original, similar to how a two-dimensional hologram can show three-dimensional detail. .

Maria Spiropulu of the California Institute of Technology and her colleagues used Google’s Sycamore quantum computer to simulate a holographic wormhole – a tunnel through spacetime with black holes at each end. They simulated a type of wormhole through which a message could theoretically pass, and examined the process by which such a message could make that journey.

In a real wormhole, this travel would be mediated largely by gravity, but the holographic wormhole uses quantum effects as a substitute for gravity to remove relativity from the equation and simplify the system. This means that when the message passes through the wormhole, it actually undergoes quantum teleportation – a process by which information about quantum states can be sent between two distant but quantum entangled particles. For this simulation, the “message” was a signal containing a quantum state – a qubit in a superposition of 1s and 0s.

“The signal gets scrambled, it becomes mush, it becomes chaos, then it comes back up and appears pristine on the other side,” Spiropulu says. “Even on this small system, we could sustain the wormhole and observe exactly what we expected.” This happens due to the quantum entanglement between the two black holes, which keeps information falling at one end of the wormhole at the other end. This process partly explains why a quantum computer is useful for this type of experiment.

The simulation only used nine quantum bits, or qubits, so it was very low-resolution. Like a photo of a bird taken from afar, this one had the same general shape as the object it depicted, but the simulation had to be carefully adjusted to display the characteristics of a wormhole. “If you want to see this as a wormhole, there are a number of parallels, but it’s definitely a matter of interpretation,” says Adam Brown of Stanford University in California, who did not participate. to this work.

Using a more powerful quantum computer could help bring the picture into focus. “This is just a baby wormhole, a first step in testing quantum gravity theories, and as quantum computers evolve we need to start using larger quantum systems to try to test the most great ideas of quantum gravity,” says Spiropulu.

This is crucial because some theories of quantum gravity are difficult or even impossible to fully understand using classical computing alone. “We know that quantum gravity is very confusing, theory can be very difficult to extract from predictions, and the dream would be to do something on a quantum computer that tells you things you don’t already know about quantum gravity” , says Brown. . “It’s not that – it’s a very small quantum computer, so everything is entirely possible to simulate on a laptop without the fan even starting.”

But the similarity of the simulation to a real wormhole suggests that it might be possible to use quantum computers to formulate and test ideas about quantum gravity, and perhaps eventually to understand it.

Journal reference: NatureDOI: 10.1038/s41586-022-05424-3