Atom counts reveal temperature in ultracold quantum gases

Researchers at Laboratoire Kastler Brossel have developed a new way to measure temperature in ultracold quantum gases by analyzing number fluctuations within probe volumes containing, on average, only one atom. This novel in-situ thermometry, demonstrated on an ideal Fermi gas using quantum gas microscopy, moves beyond the limitations of established methods requiring global thermal equilibrium. Unlike traditional techniques, the work, which extracts both global and local temperatures, does not rely on the fluctuation-dissipation theorem, instead utilizing the relationship between number fluctuations and density-density correlations. This nearly universal thermometer. The approach allows for both global and local temperature determination across a broad dynamic range, a capability previously limited…