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

[KevinOwens]

Strontium atoms in laser tweezers are the same basic setup many neutral atom quantum computers use. Progress in one helps the other

Caltech has been a leader in this for years. Endres's group in particular keeps producing big results

[LostPete10]

Six thousand one hundred atoms in one array is the number that jumped out. That was unthinkable a few years ago

[Transformer Elk]

Forty years between prediction and measurement is a long wait. Fair play to the theorists who got it right without ever seeing proof

Physics has a lot of these patient success stories, the Higgs boson being the famous one. Peter Higgs waited nearly fifty years for his

[Neil57]

Thirty five atoms does not sound like many, but controlling them that precisely is incredibly hard. Each one has to be placed and tuned exactly. Scaling to thousands while keeping that control is the big challenge for the field

Every extra atom adds complexity. Error rates creep up fast

[Tracey99]

This kind of research is why university funding matters. There is no product at the end of it, just better understanding of how nature works

Those discoveries often turn into technology decades later, in ways nobody can predict. Lasers and GPS both came out of curiosity driven physics. Nobody planned them

[KeyboardWarrior]

Quantum simulators do not get enough attention. Everyone talks about quantum computers, but simulators are already producing real science. They are built to answer one type of question very well. That focus makes them useful much sooner

[Router53]

I had to look up the tricritical Ising model. Not going to pretend I followed all of it, but the idea of energy levels forming a ladder with fixed ratios is easy enough to picture

Nice to read a quantum story without any hype about breaking encryption. More of this kind of story please

[GateWalker31]

Poke and prod is a lovely way of describing experimental physics. Theory can be elegant, but you only trust it once nature agrees. That is the whole point of science. Theorists need experimentalists as much as the reverse