Transit Noise in Spin Squeezing Experiments with Coated Rubidium Vapor Cell

Abstract

Spin squeezing can suppress quantum projection noise via interparticle entanglement, therefore enabling measurement sensitivities beyond the standard quantum limit. In practice, however, the Gaussian and finite intensity profiles of the optical probe beam induce spatially inhomogeneous atom-light interactions. As polarized atoms move within a vapor cell, they experience position-dependent optical intensities, generating transit noise that limits spin squeezing performance. Here, we investigate the transit noise in a coated rubidium vapor cell through combined theoretical analysis and experimental measurements. By varying the probe beam diameter, we quantify the dependence of transit noise on beam size and atomic Larmor frequency. Our results show that, for a vapor cell with fixed dimensions, the transit noise increases as the probe beam spot area decreases. Moreover, when the Larmor frequency is below the characteristic linewidth of the transit noise, the noise contribution becomes larger. We further calculated and measured spin squeezing for different beam sizes and found an experimental difference of $2.7\pm 0.2$ dB between 2~mm and 0.6~mm, similar to the theoretical prediction of $3.0\pm 0.3$ dB. Theoretical analysis under conditions of stronger squeezing shows that transit noise becomes an even more critical limiting factor. These results provide practical guidance for optimizing probe beam parameters and suppressing transit noise in spin squeezing experiments.

16 pages,7 figures, 3 appendix figures

References in corpus (21)

• Quantum metrology with nonclassical states of atomic ensembles
• Quantum interface between light and atomic ensembles
• An Optical Lattice Clock with Accuracy and Stability at the $10^{-18}$ Level
• An atomic clock with $10^{-18}$ instability
• Implementation of Cavity Squeezing of a Collective Atomic Spin
• States of an Ensemble of Two-Level Atoms with Reduced Quantum Uncertainty
• Magnetic sensitivity beyond the projection noise limit by spin squeezing
• Deterministic entanglement generation from driving through quantum phase transitions
• Reduced back-action for phase sensitivity 10 times beyond the standard quantum limit
• Measurements with prediction and retrodiction on the collective spin of 10^{11} atoms beat the standard quantum limit
• Past quantum states
• Generation of a squeezed state of an oscillator by stroboscopic back-action-evading measurement
• Distributed quantum sensing with a mode-entangled network of spin-squeezed atomic states
• Quantum-enhanced sensing on an optical transition via emergent collective quantum correlations
• Spin Squeezing by Rydberg Dressing in an Array of Atomic Ensembles
• Off resonance laser frequency stabilization using the Faraday effect
• Entanglement-enhanced radio-frequency field detection and waveform sensing
• Noise analysis of the atomic superheterodyne receiver based on flat-top laser beams
• Continuous field tracking with machine learning and steady state spin squeezing
• Concurrent spin squeezing and light squeezing in an atomic ensemble
• Squeezed light from an oscillator measured at the rate of oscillation