Physicists measure the energy ladder in a quantum simulator for the first time — ScienceAlert

A team of scientists led by researchers at the California Institute of Technology has experimentally measured for the first time a characteristic structure of energy levels predicted in 1984. A quantum simulator with a chain of strontium atoms was used for the experiment. ScienceAlert reports.

A theoretical prediction tested in an experiment

The research concerns conformal field theories that describe the phenomenon of universality: near critical points, different materials can behave similarly. Examples of such transitions include water boiling or a magnet losing its magnetic properties.

In 1984, physicist John Cardy used the mathematical framework of conformal field theories to predict that systems at critical points would absorb energy according to fixed patterns. Researchers compare these sequences of energy levels to the rungs of a ladder. Previously, this structure had been described theoretically but had not been directly observed or measured.

Chains of up to 35 atoms

In the quantum simulator, strontium atoms were held and arranged using laser light. Other lasers transferred them into high-energy Rydberg states, which enhanced interactions between the atoms. This made it possible to tune the chain of atoms close to a critical point, after which the lasers were modulated at different frequencies, revealing the rungs of the energy ladder.

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The experiments were conducted on chains of up to 35 atoms. For the Ising point, the obtained spectra, after scaling by size, collapsed onto one universal curve, as predicted by the corresponding conformal field theory. The team also tuned the system to a tricritical point and measured the lowest levels of its spectrum; their ratios matched the theoretical prediction.

Applications of quantum platforms

The results, published in the journal Nature, may help study the behavior of materials near quantum critical points at temperatures close to absolute zero. The authors believe that the method can also be used for other quantum critical systems, including those where the exact answer is not known in advance or where classical computers cannot perform the necessary calculations.

The scientists also noted that tools borrowed from quantum computing platforms can already be used for fundamental physics research. A related quantum platform in the same laboratory had previously managed to hold 6,100 atoms in an array.