Quantum lock-in detection of a vector light shift

TL;DR

This paper introduces a quantum lock-in technique for highly precise detection of vector light shifts in Bose-Einstein condensates, achieving sub-Hz resolution and enabling long coherence times by polarization control.

Contribution

The study presents the first application of quantum lock-in detection to measure and eliminate vector light shifts in BECs, enhancing measurement precision and coherence.

Findings

Detected VLS with less than 1 Hz resolution

Successfully eliminated VLS via polarization control

Extended coherence time of BEC by VLS suppression

Abstract

We demonstrate detection of a vector light shift (VLS) using the quantum lock-in method. The method offers precise and accurate VLS measurement without being affected by real magnetic field fluctuations. We detect a VLS on a Bose--Einstein condensate (BEC) of $^{87}$Rb atoms caused by an optical trap beam with a resolution less than 1 Hz. We also demonstrate elimination of a VLS by controlling the beam polarization to realize a long coherence time of a transversally polarized $F$ = 2 BEC. Quantum lock-in VLS detection should find wide application, including the study of spinor BECs, electric-dipole moment searches, and precise magnetometry.