Quantum computers are used to model wormholes

Physicists, mathematicians, astronomers, and even filmmakers have long been fascinated by the concept of a wormhole: an unpredictable and often fleeting phenomenon thought to create tunnels (and shortcuts between two distant locations) through spacetime. Another theory is that if you properly connect two black holes together, you can create a wormhole.

Studying wormholes is like putting together an incomplete jigsaw puzzle without knowing what the final picture should look like. You can roughly deduce what should go in the gaps based on the finished images around them, but you can’t know for sure. That’s because there’s still no definitive proof that wormholes actually exist. However, some of the solutions to fundamental equations and theories in physics suggest that such an entity exists.

To understand the properties of this cosmic phantom based on what has been inferred so far, researchers from Caltech, Harvard, MIT, Fermilab and Google have created a small “wormhole” effect between two quantum systems sitting on the same processor. It also allowed the team to send a signal.

Corresponding quantumThis puts the Caltech-Google team ahead of an IBM-Quantinuum team that has also attempted to establish wormhole teleportation.

Though what they have created is unfortunately not a true rip through the fabric of space-time, the system mimics the well-known dynamics of wormholes. In terms of properties that physicists typically consider, such as positive or negative energy, gravity, and particle behavior, the computer simulation effectively looks and functions like a tiny wormhole. This model, the team said in a news conference, is a way to study the universe’s fundamental problems in a laboratory setting. A paper describing this system was published in the journal this week Nature.

“We have found a quantum system that has key properties of a gravitational wormhole but is small enough to implement on today’s quantum hardware,” said Maria Spiropulu, a physics professor at Caltech, in a press release. “This work represents a step towards a larger program to test quantum gravity physics with a quantum computer.”

[Related: Chicago now has a 124-mile quantum network. This is what it’s for.]

Quantum gravity is a set of theories that postulate how the rules of gravity (which describes how matter and energy behave) and quantum mechanics (which describes how atoms and particles behave) fit together. Researchers don’t yet have the exact equation to describe quantum gravity in our universe.

Although scientists have pondered the relationship between gravity and wormholes for around 100 years, it wasn’t until 2013 that entanglement (a phenomenon of quantum physics) was thought to play into the connection. And in 2017, another group of scientists proposed that traversable wormholes work similarly to quantum teleportation (where information is transported through space using entanglement principles).

In the latest experiment, which runs on just 9 qubits (the quantum equivalent of binary bits in classical computing) in Google’s Sycamore quantum processor, the team used machine learning to set up a simplified version of the wormhole system “that could be encoded in stream quantum architectures.” and that would preserve the gravitational properties,” Spiropulu explained. During the experiment, they showed that information (in the form of qubits) can be sent through one system and reappear on the other system in the correct order – behavior akin to a wormhole.

[Related: In photos: Journey to the center of a quantum computer]

So how do researchers go about setting up a small universe in a box with its own special set of rules and geometries? According to Google, a special type of correspondence (technically known as AdS/CFT) between different physical theories allowed scientists to construct a hologram-like universe in which they can “connect objects in space with specific ensembles of interacting qubits on the surface.” Researchers wrote in a blog post. “This allows quantum processors to work directly with qubits while providing insights into space-time physics. By carefully defining the parameters of the quantum computer to emulate a particular model, we can look at black holes or even go further and look at two black holes connected to each other – a configuration known as a wormhole.”

Researchers used machine learning to find the perfect quantum system that preserves some key gravitational properties and maintains the energy dynamics the model was intended to represent. They also had to simulate particles called fermions.

The team noted in the press conference that there is strong evidence that our universe operates according to rules similar to the hologram universe observed on the quantum chip. The researchers wrote in the Google blog post: “Gravity is just one example of the unique ability of quantum computers to probe complex physical theories: quantum processors can provide insights into time crystals, quantum chaos and chemistry.”

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