Scientists Think the Secrets of Our Universe Could Be Contained in One Tiny Qubit

A new paper gives fellow quantum physicists a tool to help explore the geometry of the universe.
They say one qubit’s behavior, regardless of its starting position, forms a predictable geometric idea.
This research is not yet peer reviewed, and is in a shorter format referred to as a letter.

Is there a chance that the secrets of our universe are contained in some of its smallest, newest components: the quantum bit, or qubit? In a recent paper exploring the spirit of this question, uploaded to the preprint server arXiv, quantum physicists James Fullwood and Vlatko Vedral suggest that spacetime itself may be a large-scale rendering of tiny quantum changes within time that could be found on these microscopic devices. After all, qubits are simple enough to be one logical bit in a quantum computer, but robust enough to embody quantum mechanics principles like superposition.

The theory sounds (and is!) far out, but it joins a growing discussion about the nature of spacetime. As quantum and classical physicists continue to search for the union between their separate sets of ideas, we know after nearly 100 years of work that spacetime is more of a shorthand for something we don’t understand yet. Cosmologists continue to wind time backward as best they can, but there’s much we will never be able to study or verify about where our universe came from—or what it really is or isn’t.

“There is a growing consensus in theoretical physics that spacetime is not a primitive notion,” Fullwood and Vedral explain, meaning that the universe is not as intuitive, or apparent, as people have guessed by looking at the sky. Is there an “I think, therefore I am” Descartes moment for the universe?

In their research, the scientists found that a single qubit acting within its phase space (the mathematical set of all the physical states a system can take) over time draws out what is known as a three-dimensional Euclidean space—one which has comparable qualities to the universe overall. The shape created had those same qualities regardless of the qubit’s starting position, meaning that the complex waveforms created by a single qubit’s behaviors over time and within space did not matter.

Curiously, the scientists say that this setup of one qubit is the only one they can imagine where a specific quantum function called the two-time correlation function matches with a particular measurement of Euclidean geometry. In the world of quantum physics, descriptions of systems are often very abstract, with calculations that can rise into many dimensions. In this case, the qubit’s behavior lines up with the way we describe spacetime using regular Euclidean geometry.

To illustrate the theory, Fullwood and Vedral used a ‘toy model’ of a one-qubit universe. A toy model is an extremely simplified version, usually to show one or two key mechanics without other variables. The toy qubit universe “serves as a reservoir from which an observer may extract the information necessary for a geometric structure to emerge,” they concluded. “[T]he question remains as to how the metric of spacetime [emphasis theirs] may emerge in such a framework, and more generally, how gravity may enter the picture.”

This paper is intended as a letter, meaning that is a shorter piece meant to appear in a peer reviewed journal with a small page limit. If it’s peer reviewed and published, the work could slot into future research and lead to further conclusions about gravity and other missing pieces. Often, the hope is to give colleagues a tool or thought exercise that will shake loose the next step toward a bigger breakthrough—like using a system of two equations to substitute and solve for two variables.

The researchers hint at this themselves with a concluding thought:

“Archimedes is said to have summarized his discovery via the poetic statement ‘Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.’ [W]e summarize this Letter with the following statement: ‘Give me a qubit for long enough and a probe in which to measure it, and I shall extract the geometry of our world.’”

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