Spin-squeezing swapping for differential measurements with atom interferometers and clocks
Résumé
Thanks to common-mode noise rejection, differential configurations are crucial for realistic applications of phase and frequency estimation with atom interferometers. Differential interferometry can be understood as a distributed multiparameter estimation problem and can benefit from both mode and particle entanglement. Currently, differential protocols with uncorrelated particles and mode-separable settings reach a sensitivity bounded by the standard quantum limit (SQL). Here, we propose to overcome the SQL by exploiting spin-squeezing in an atomic quantum network. A single spin-squeezed state is mode-swapped among common interferometric modes. The mode swapping is optimized to estimate the differential phase shift with sub-SQL sensitivity. Numerical calculations are supported by analytical approximations that guide the optimization of the protocol. The scheme is also tested with simulation of noise in atomic clocks and interferometers.