Determining the atom number from detection noise in a one-dimensional optical lattice clock

Abstract

In this paper, we demonstrate in situ synchronous frequency comparison between distinct regions in a one-dimensional optical lattice. The synchronous comparison instability is well below the Dick limit and agrees with the limit induced by atomic detection noise. The absolute atom number is extracted from the synchronous comparison instability with an uncertainty below 3%. Surpassing the performance of absorption imaging, this method provides a way to directly and precisely determine the absolute atom number from detection noise. Taking advantage of the inhomogeneous density distribution over the whole lattice, the density shift can also be conveniently measured by this synchronous frequency comparison method. Inconsistent with the expectation of the linear relationship between density shift and atom number difference, nonlinearity is observed, indicating that the assumption of an identical density shift coefficient over the whole lattice is not always safe.

Noise Differentiation and Atom Number Measurement in Optical Lattice Clocks by Analyzing Clock Stabilities with Various Parameters

“…In step 2, the clock comparison process between two clocks is executed with a total measurement time of approximately 2.2 hours, where the Dick effect is cancelled by setting the clock laser noise to be zero [27]. The cancellation of the Dick effect is realized in experiment by synchronous frequency comparison between two clocks [23,28] or using the in situ imaging technique to compare two regions of cold ensembles in a clock [18,19,22,25]. Three cases with noise amplitudes of σa, σb, and σc are simultaneously simulated.…”

Noise Differentiation and Atom Number Measurement in Optical Lattice Clocks by Analyzing Clock Stabilities with Various Parameters

“…In this work, the Dick effect is cancelled by setting the clock laser noise to be zero [27]. The cancellation of the Dick effect can be realized in experiment by synchronous frequency comparison between two clocks [23,28], or by using the in situ imaging technique to compare two regions of cold ensembles in a clock [18,19,22,25]. Regarding the simulation aspect of the in-loop clock operation, the excitation fractions at half-height points are determined by adjusting the center frequency of the Rabi spectrum by ±0.4/T p .…”

“…This progress has spurred the development of a new method to measure the atom number based on QPN. The previous method of measuring atom numbers from atomic detection noise required the neglect of technical noise [22]. This prerequisite prevented the utilization of atom number measurement based on the QPN.…”