Researchers used optical‑tweezer arrays of strontium atoms driven into Rydberg states to reproduce two conformal field theories and directly measure the predicted energy ratios at quantum critical points.
For the first time, experimentalists measured the energy‑level ratios predicted by Ising and tricritical Ising conformal field theories.
The team used optical tweezer arrays of strontium atoms, drove them to interacting Rydberg states, and tuned lasers to reach quantum critical points near absolute zero.
They detected the energy ladder with a technique called many‑body modulation spectroscopy, scanning drive frequencies and reading resonant responses.
# What happened Caltech researchers reported the first direct measurements of an energy spectrum that conformal field theory predicted about 40 years ago. They recreated two different conformal field theories—the Ising and the tricritical Ising cases—on a purpose‑built quantum simulator and observed the excitation energies fall into the precise ratios the theory predicts.
# Why it matters
# How the experiment worked The team arranged strontium atoms in a one‑dimensional chain using optical tweezers. They used additional lasers to excite atoms into Rydberg states, where neighboring atoms interact strongly and the chain behaves collectively. By adjusting laser parameters the researchers tuned the system to the quantum critical points corresponding to the Ising and tricritical Ising conformal field theories.
To reveal the hidden energy ladder they developed many‑body modulation spectroscopy. The method gently perturbs the whole atomic chain at a chosen frequency and measures the system's response. As the drive frequency is scanned, peaks in the response identify excitation energies much like a resonant note reveals a glass's natural frequency.
# Who did it The experiment combined the experimental group of Manuel Endres at Caltech, Jason Alicea's theory group at Caltech, and theorists at Université Paris‑Saclay and the Technical University of Munich. The results appear in Nature.
# Main results The researchers observed excitation levels in the synthetic quantum matter that matched the precise ratios predicted by the Ising and tricritical Ising conformal field theories. These ratios had been calculated theoretically for about four decades but had not been directly measured in a controlled experiment until now.
# What this enables next The quantum simulator platform and the spectroscopy technique can now be applied to other quantum critical systems where theoretical answers are unknown or difficult to obtain. The approach leverages neutral‑atom optical tweezer arrays—technology developed in part for quantum computing—but repurposes it to study fundamental quantum many‑body physics.
# Bottom line The experiment turns a long‑standing theoretical prediction into an experimentally observed spectrum. It demonstrates that modern neutral‑atom quantum simulators can access and verify universal quantum properties at critical points, opening a path to study other complex quantum systems with experimental control.
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