Caltech physicists have made the first direct measurement of the energy levels predicted by the Ising and tricritical Ising conformal field theories, a set of predictions that stood untested in experiments for roughly 40 years. The work, with partners at Université Paris-Saclay and the Technical University of Munich, appeared in Nature.
The team trapped chains of up to 35 strontium atoms with laser optical tweezers. A technique called many-body modulation spectroscopy shook the chain by modulating the lasers at a chosen frequency, then measured how strongly the atoms responded. The spacings between the energy levels matched theory, and the spectra collapsed onto a single universal curve once rescaled for system size.
The result shows that quantum simulators can test universal rules of quantum matter directly. Next, the researchers plan to move from one-dimensional chains to two-dimensional atom grids, where the physics is far less understood.