0:00 intro 0:54 Wormholes and entanglement 2:56 Quantum gravity on a chip? 3:59 Not a wormhole 5:14 No wormholes, but still impressive ---------------------------- Did physicists make a wormhole in the lab? short answer is Not quite Scientists made headlines last week for supposedly generating a wormhole. The research, reported , involves the use of a quantum computer to simulate a wormhole in a simplified model of physics. Soon after the news broke, physicists and experts in quantum computing expressed scepticism that a wormhole had in fact been created. Media coverage was chaotic. Outlets reported that physicists had created a theoretical wormhole, a holographic wormhole or perhaps a small, crummy wormhole, and that Google’s quantum computer suggests wormholes are real. Other outlets soberly offered the news that no, physicists didn’t make a wormhole at all. If this has you confused, you’re not alone! What’s going on? Wormholes and entanglement The Universe is vast. It’s so big that travelling from one side to the other by conventional means is impractical. Wormholes are a kind of loophole: shortcuts between two regions of the Universe that might allow one to traverse vast distances in a much shorter time. Wormholes are permitted by Einstein’s theory of relativity, but none have ever been found in nature. Recently, physicists have been toying with the idea that wormholes are related to another phenomenon, known as entanglement. Entanglement is a peculiar, quantum phenomenon involving particles. When particles are put into an entangled state, measurement of one particle seems to affect the other particle immediately. This is the case even when the two particles are too far apart for causation to be possible. Some physicists have suggested that a wormhole may just be a way of describing a certain kind of quantum entanglement. If correct, this would forge a link between two prominent theories of physics: quantum mechanics and general relativity. General relativity explains how gravity works, and describes the Universe on large scales. Quantum mechanics explains the other fundamental forces, and describes the Universe on very small scales. Both are extremely successful theories. However, they are yet to be reconciled into a single, unified theory. A unified theory would preserve the insights of both quantum mechanics and general relativity, while at the same time providing an account of how gravity works in the quantum domain, something we don’t currently understand. Because wormholes are distinctive of general relativity, and entanglement is distinctive of quantum mechanics, the potential similarity between them is exciting. It suggests the two theories may, at some level, be describing the very same thing. Quantum gravity on a chip? How would we look for this potential similarity between wormholes and entanglement? Well, we know how to entangle particles experimentally. We’ve been doing that for some time. So we can try to build a particular kind of quantum system: one that can be described using the same physics we use for wormholes. If we can build such a system in the lab and it behaves like a wormhole, it would support the idea that entanglement and wormholes are two sides of the same coin. In quantum computers, the basic components can be put into various quantum states that can be used to run quantum experiments. So, it seems they present an opportunity to test the relationship between wormholes and entanglement. This is perhaps why it was reported that physicists had used a quantum computer to generate a wormhole. But that does not seem to be what actually happened, though understanding why is not straightforward. Not a wormhole What physicists did was organise 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 through the quantum system. The quantum system, and the way the information was transferred, can be described using a particular model in physics. According to this model, the kind of information transfer that occurred within the computer is descriptively similar to the way that something passes through a wormhole. However, the model being used has at least two limitations. First, it appears 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 while we can describe what happened within the computer as though it were a wormhole, using a specific kind of model, it is unclear whether the model represents the world as we know it. No wormholes, but still impressive