Multi-second magnetic coherence in a single domain spinor Bose-Einstein condensate

TL;DR

This paper presents a robust system for studying magnetic dynamics in a spinor Bose-Einstein condensate, achieving multi-second magnetic coherence times using non-destructive Faraday rotation probing.

Contribution

It introduces a novel optical trapping and probing method enabling long-lived magnetic coherence in a spinor BEC.

Findings

Magnetic T1 and T2* coherence times reach several seconds.

Non-destructive Faraday rotation allows real-time magnetization tracking.

The system demonstrates stable, long-duration magnetic measurements in a BEC.

Abstract

We describe a compact, robust and versatile system for studying magnetic dynamics in a spinor Bose-Einstein condensate. Condensates of 87 Rb are produced by all-optical evaporation in a 1560 nm optical dipole trap, using a non-standard loading sequence that employs an auxiliary 1529 nm beam for partial compensation of the strong differential light shift induced by the dipole trap itself. We use near-resonance Faraday rotation probing to non-destructively track the condensate magnetization, and demonstrate few-Larmor-cycle tracking with no detectable degradation of the spin polarization. In the ferromagnetic F = 1 ground state, we observe magnetic T1 and T2$^*$ coherence times limited only by the several-second residence time of the atoms in the trap.