Caltech physicists measure a quantum 'energy ladder' predicted 40 years ago

[MachineSaint]

ScienceDaily has a great physics story from Caltech. A team led by experimental physicist Manuel Endres and theorist Jason Alicea, working with researchers from Universite Paris-Saclay and the Technical University of Munich, has directly measured a pattern of quantum energy levels that theory predicted around 40 years ago. The results are published in Nature. It is the kind of result that sounds abstract but matters a lot to physicists

The predictions come from conformal field theory, a framework that describes how systems behave at quantum critical points, the knife edge moments where a material is about to switch from one phase to another. At those points, the theory says energy levels should line up in a very specific ladder with fixed ratios between the rungs. Physicists have relied on that maths for decades without being able to check it so directly. If the experiment had disagreed, a lot of textbooks would need rewriting

To test it, the team built a quantum simulator using strontium atoms held in place by laser tweezers and arranged in chains of up to 35 atoms. They tuned the chains to critical points described by two models, the Ising model and the more complex tricritical Ising model, then measured the energy levels. The ratios matched the theoretical predictions. That is a remarkably clean confirmation for something this subtle. Physicists will be delighted

The same group recently made headlines by trapping 6,100 atoms in a single array, so this technology is scaling quickly. Alicea put it nicely, saying that even though they believed the theories were true, it is important to have an experimental version you can poke and prod. That is how physics should work, with theory and experiment checking each other

It also links to the neutral atom quantum computers we have been discussing, from Pasqal to Japan's Shunkai, since they use very similar techniques. Simulators like this may be useful well before full quantum computers are. Does anyone here follow this side of physics?

Caltech physicists finally measure a quantum energy ladder predicted 40 years agowww.sciencedaily.com