Wormhole simulation may have been wrong – New Scientist

When Google’s quantum computer simulated a wormhole at the end of last year, it made headlines worldwide. However, a new study questions the simulation.

The first simulation of a wormhole on a quantum computer may not have accurately represented such a tunnel in spacetime after all. The simulation made headlines last year, but now another group of researchers has investigated the simulation. They found a number of problems that undermine the claim that it was a successful simulation.

The simulation shows a so-called ‘holographic wormhole’. The word ‘holographic’ refers to a way of simplifying physics problems using techniques from quantum mechanics. That simplification was applied here, but importantly, the simpler, holographic version of the wormhole is still complex enough to say something about the original. Just as a two-dimensional hologram can reveal something about the three-dimensional details of an object.

Wormhole claim

In November 2022 made physicist Mary Spiropulu of the California Institute of Technology and colleagues revealed that they had used Google’s quantum computer, Sycamore, to simulate a holographic wormhole. They also said they sent signals through the simulated wormhole. They did this with quantum teleportation, a phenomenon in which information about a quantum state is sent on one side of the system and emerges on the other.

The researchers said the results of the simulation turned out as expected. Now have physicist Norman Yao of the University of California, Berkeley, and colleagues reviewed the details of the study. They found three major problems which they say proves that the simulation doesn’t do a good job of showing how wormholes behave.

Three problems

The first problem has to do with how the simulated wormhole responded to the signals sent through it. The theory says this would cause fluctuations in the system. It’s like the wormhole is shaking, but it should eventually settle down. In the original study, this actually seemed to happen, but only when the researchers averaged over many different tests. When Yao and his colleagues looked at each test individually, the wormhole vibrated indefinitely. That doesn’t fit the expectations of how a wormhole behaves.

The second problem was about the signals themselves. One of the hallmarks of a real wormhole – and therefore a good holographic wormhole – is that the signal coming out looks the same as it did when it went in. Yao and his team found that this was true for some signals, but not all. The signal remained the same only when it resembled the signals the researchers had also used in the algorithm that simplified the system

The last, biggest problem, concerns a quantum phenomenon that winding size is called. Size winding occurs when a holographic image correctly represents a particular gravity situation, such as a wormhole. In the system under investigation, the winding size however, if the model was made larger or more detailed. The throbbing winding size that the first researchers saw may therefore have arisen only by chance at a specific size of the model.

Less confidence

Spiropulu responds that these problems do not apply to the entire simulation, but only to individual parts of it. ‘The researchers say something about it [de gecombineerde eigenschappen van de simulatie], while they only look at the individual quantum systems of our model,’ she says. She insists that “we observed properties consistent with wormhole teleportation.”

However, other experts have also expressed their doubts about the simulation. Physicist John Prekill of CalTech says he now has “less confidence in the evidence.”

Physicist Leonard Suskind of Stanford University in California believes the experiment did simulate a wormhole, but only in the broadest sense of the word. What is not so clear is whether the experiment is better than conventional quantum teleportation experiments, and whether it actually captures the features of general relativity that the authors claim. That is only the case in a vague way,’ he says.

Similar experiments in the future could teach us a lot about the properties of wormholes, says Susskind. They will have to be more complex than this experiment before we can really extract new information from them.