Thermometry via Light Shifts in Optical Lattices

Abstract

For atoms or molecules in optical lattices, conventional thermometry methods are often unsuitable due to low particle numbers or a lack of cycling transitions. However, a differential spectroscopic light shift can map temperature onto the line shape with a low sensitivity to trap anharmonicity. We study narrow molecular transitions to demonstrate precise frequency-based lattice thermometry, as well as carrier cooling. This approach should be applicable down to nanokelvin temperatures. We also discuss how the thermal light shift can affect the accuracy of optical lattice clocks.

Light-shift spectroscopy of optically trapped atomic ensembles

“…A similar demonstration of this concept has been shown by McDonald et al as a tool for thermometry of ultra-cold molecules in an optical lattice [33]. Here we show that our approach has a much broader applicability beyond circumstances in which atoms are held in the tightly confined Lamb-Dicke regime.…”

Cooling and thermometry of atomic Fermi gases

“…This indicator can be measured by determining the number of molecules produced in the strong coupling limit provided by a Feshbach resonance. Other thermometry methods recently proposed involve the determination of the width of the intermediate magnetization region for two spatially separated spin-polarized components [213,214], the measurement of spatially resolved density and the related number fluctuations [215], Ra- man spectroscopy [216], light diffraction [217] and light shifts [218], the response of the Fermi gas to an artificial gauge field [219], and lattice amplitude modulation [220]. The general issue with many of these measurement techniques, as emphasized in [34], is that a network of benchmarks is required for calibration purposes, and preferably they should not be model-dependent, or at least they should not rely on the same physics to be explored to avoid circularity.…”

High-precision spectroscopy of ultracold molecules in an optical lattice

“…The progress described here lays the foundation for these fruitful research directions. are mostly limited by thermal decoherence from differential lattice light shifts [30]. For this trace, the experimental conditions were adjusted to achieve a narrow width, and a Lorentzian fit to the natural logarithm of the data (to account for linear probe absorption) yields a 112(8) Hz FWHM.…”