Have physicists dug a wormhole in the lab?  Not quite, but a new experiment hints at the future of quantum simulations

Have physicists dug a wormhole in the lab? Not quite, but a new experiment hints at the future of quantum simulations

Scientists made headlines last week for allegedly generating a wormhole. The research, reported in Nature, involves using a quantum computer to simulate a wormhole in a simplified physics model.

Shortly after the news broke, physicists and quantum computing experts expressed skepticism that a wormhole had been created.

Media coverage was chaotic. Outlets have reported that physicists have created a theoretical wormhole, a holographic wormhole, or possibly a small, shabby wormhole, and Google’s quantum computer suggests wormholes are real. Other media soberly announced that no, the physicists had not made a wormhole at all.

If this has you confused, you’re not alone! What’s going on?

Wormholes and tangles

The Universe is vast. It is so large that traveling from side to side by conventional means is impractical.

Wormholes are a kind of loophole: shortcuts between two regions of the Universe that could make it possible to travel vast distances in a much shorter time. Wormholes are allowed by Einstein’s theory of relativity, but none have ever been found in nature.

An illustration showing a wormhole joining dots in space.
A wormhole is a hypothetical “shortcut” between two regions of space.

Recently, physicists have toyed with the idea that wormholes are related to another phenomenon, known as entanglement.

Entanglement is a particular quantum phenomenon involving particles. When particles are put into an entangled state, the measurement of one particle seems to immediately affect the other particle. This is the case even when the two particles are too far apart for causality to be possible.

Some physicists have suggested that a wormhole might just be a way of describing some type of quantum entanglement. If correct, it would link two important theories of physics: quantum mechanics and general relativity.

General relativity explains how gravity works and describes the large-scale Universe. Quantum mechanics explains the other fundamental forces and describes the Universe on very small scales.

Illustration showing two glowing particles connected by faint lines.
In quantum mechanics, “entanglement” is a kind of connection between particles that can be quite far from each other.

Both are extremely successful theories. However, they have yet to be reconciled into one unified theory.

A unified theory would preserve both the knowledge of quantum mechanics and general relativity, while accounting for how gravity works in the quantum realm, something we currently don’t understand.

Because wormholes are distinctive of general relativity and entanglement is distinctive of quantum mechanics, the potential similarity between them is exciting. This suggests that the two theories can, on some level, describe exactly the same thing.

Quantum gravity on a chip?

How would we look for this potential similarity between wormholes and entanglement?

Well, we know how to experimentally entangle particles. We have been doing this for some time.

So we can try to build a particular type of quantum system: a system that can be described using the same physics that we use for wormholes. If we can build such a system in the lab and have it behave like a wormhole, that would support the idea that entanglement and wormholes are two sides of the same coin.

Read more: Explainer: quantum computing and communication technology

In quantum computers, the basic components can be placed in various quantum states which can be used to perform quantum experiments. So it looks like they present an opportunity to test the relationship between wormholes and entanglement.

Perhaps that is why physicists have been reported to have used a quantum computer to generate a wormhole. But that doesn’t seem to be what really happened, although understanding why isn’t straightforward.

Not a wormhole

What physicists have done is organize the basic components of a quantum computer into a specific quantum state. They were then able to transfer information from one part of the computer to another via the quantum system.

The quantum system and the way the information was transferred can be described using a particular physical model. According to this model, the type of information transfer that has occurred in the computer is descriptively similar to how something passes through a wormhole.

Read more: What are wormholes? An astrophysicist explains these shortcuts through space-time

However, the model used has at least two limitations.

First, it seems to make unrealistic assumptions about the physics of our world. It assumes, in particular, that spacetime – the fabric of the Universe – has certain properties that it may not have.

Second, the model has been simplified to describe a simple system that can be implemented with a quantum computer. Such a simplified model may be physically inaccurate.

So, although we can describe what happened in the computer as if it were a wormhole, using a specific type of model, it is not clear if the model represents the world as we know it.

Experimentation and simulation

Some commentators have offered a different reason to be skeptical about the creation of a wormhole: it was just a simulation. As one reviewer put it, viewing the system as a wormhole “is like claiming that playing the Portal video game involves creating an actual wormhole because it represents something resembling the theoretical concept on the screen. “.

We must indeed be careful before drawing conclusions about reality from simulations. However, the quantum aspect of this simulation makes it more of an experiment than a regular simulation you might run on a regular computer.

It therefore seems that the simulation can legitimately tell us something about the quantum system it is simulating. However, the problem remains that we can only interpret the system as a wormhole in a specific and potentially unrealistic model of physics.

No wormholes, but still impressive

So maybe we should be skeptical about creating wormholes. Still, there is something to be impressed about.

For one, the team used machine learning techniques to simplify the model they were using to simulate it in a useful way.

Using machine learning to produce the simplified model is interesting, and we should expect to see more uses of machine learning like this in the future.

It is also important that a quantum computer was used to perform the type of quantum experiment in question. The fact that it can be done opens the door to new experiences. This can open up an experimental paradigm that can be used to advance physics.

There is also the possibility – albeit rather remote – that certain aspects of the model that has been used to describe the quantum system are justified. This could lead to the discovery of a relationship between quantum entanglement and wormholes in the future.

But that is still very speculative.

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