Physicist built a toy universe that shows time could be a quantum illusion

An experiment with a toy universe made of extremely cold atoms shows how time can emerge from quantum interactions, rather than existing by default.

The passage of time may be no more than an illusion that emerges from quantum interactions between different parts of the universe — at least, that’s what happens in one cosmos toy modelan experiment that could give clues about the nature of time in our own universe.

Giovanni Barontini, from the University of Birmingham in the United Kingdom, began thinking about time while watching his six-year-old son play.

“He was building his own little universe and I was thinking it’s badThat’s more or less what we do too in our laboratories, when we built a system of ultracold atoms”, Barontini tells .

“But then I started thinking that, as a universe, this is also quite upset, because nothing much is happeningand, if nothing happens, it’s as if ottime did not pass“, says the experimental physicist.

To investigate if time is truly an illusion In these systems, Barontini then used lasers and electromagnetic forces to cool approximately 20,000 atoms of rubidium up to temperatures close to absolute zero.

Then he divided the atoms of this toy universe into two sectorsone designated “bright” and the other “dark”, in an analogy with dark matter.

This initial universe was essentially timeless and unchangingbut then Barontini used lasers to induce the two sectors to exchange atoms and thus interact at a quantum level.

This interaction altered the entropy, or disorder, of the play universe — and we know that, in our universe, time flows in the direction of increasing entropy. Thus, Barontini was able set an internal time for your play universe.

Furthermore, it could use this new time in the Schrödinger equationwhich describes how quantum systems evolve, to calculate the quantum states of atoms, verifying that coincided with the results of the experiment.

Barontini presented the results of his experiment in a paper published last week in Physical Review Research.

There is precedent for this view of time as something that arises from correlations or quantum interactions, rather than being a given: in atomic physics, the idea was first advanced by the physicist Nevill Mott in the 1930s and has been explored theoretically ever since.

Only in 2013 did Marco Genovesefrom the Italian National Institute of Metrology, and his colleagues presented the first proof of its viabilityin an experiment with entangled light particles. Here too the notion of time resulted from quantum correlations.

“The present work further develops this ideawith some significant progress”, says Genovese. In particular, the universe of cold atoms is more complex than the one made with light, and Barontini managed to make the Schrödinger equation work with the system’s internal time — something that had never been done before.

Claus Kieferfrom the University of Cologne, Germany, states that this experience of the universe of play is linked to the broader problem of how to combine gravity and quantum theory in a single theoretical framework that can apply to our universe on all scales.

This question remains open, but some physicists have suggested that such a theory would be marked by the absence of time at the most fundamental level, he says.

Barontini’s new experiment mimics this situation, but Kiefer says there are also differences; for example, as ultracold atoms move between sectors, do not interact in complex ways that would be expected in a larger universe.

But Carlo Rovellifrom the University of Aix-Marseille, in France, states that this type of experience cannot discover anything new about time, because they are built from physics we already understand.

Still, having them as imitations of major open problems can serve as inspiration on how to approach unknown physicsjust like the elusive question of quantum gravitydiz Rovelli.

For Barontini, the new study is an experimental confirmation of ideas that have existed for a long time and, as such, a demonstration that they are not completely discarded. But it’s not a confirmation that this is how time actually works at all scales, he says.

Os cosmologists, who study the entire universe instead of laboratory-made toy models, should have objections to the workpredicts Barontini.

Still, the physicist wants to explore the ultracold mini-universe further, for example using lasers to create regions from which atoms cannot move away, similar to the attraction of a black hole.