Ramsey-like measurement of the decoherence rate between Zeeman sub-levels

TL;DR

This paper introduces a Ramsey-like measurement technique to directly determine the decoherence rates between Zeeman sub-levels in rubidium vapor, revealing coherence times of 1-10 ms primarily limited by spin-exchange collisions.

Contribution

It presents a novel application of a Ramsey-like method for direct measurement of Zeeman decoherence rates in atomic vapors, improving understanding of ground state coherence.

Findings

Measured coherence times of 1-10 ms at room temperature

Identified spin-exchange collisions as the main decoherence mechanism

Demonstrated a direct measurement approach for ground state decoherence

Abstract

Two-photon processes that involve different sub-levels of the ground state of an atom, are highly sensitive to depopulation and decoherence within the ground state. For example, the spectral width of electromagnetically induced transparency resonances in $\Lambda-$type system, are strongly affected by the ground state depopulation and decoherence rates. We present a direct measurement of decay rates between hyperfine and Zeeman sub-levels in the ground state of $^{87}$Rb vapor. Similar to the relaxation-in-the-dark technique, pumping lasers are used to pre-align the atomic vapor in a well defined quantum state. The free propagation of the atomic state is monitored using a Ramsey-like method. Coherence times in the range 1-10 ms were measured for room temperature atomic vapor. In the range of the experimental parameters used in this study, the dominant process inducing Zeeman decoherence is the spin-exchange collisions between rubidium atoms.