Motional Coherence of Fermions Immersed in a Bose Gas

TL;DR

This study investigates how fermionic lithium atoms immersed in a sodium Bose-Einstein condensate maintain motional coherence, revealing that decoherence is primarily due to population relaxation and aligning well with theoretical predictions.

Contribution

It introduces a novel spin-echo-like scheme to measure motional coherence of fermions in a Bose gas and isolates bath-induced decoherence effects.

Findings

Decoherence time is near the maximum, limited mainly by population relaxation.

Experimental results agree with Fermi's golden rule-based theoretical model.

The method effectively distinguishes bath-induced decoherence from other effects.

Abstract

We prepare a superposition of two motional states by addressing lithium atoms immersed in a Bose-Einstein condensate of sodium with a species-selective potential. The evolution of the superposition state is characterized by the populations of the constituent states as well as their coherence. The latter we extract employing a novel scheme analogous to the spin-echo technique. Comparing the results directly to measurements on freely-evolving fermions allows us to isolate the decoherence effects induced by the bath. In our system, the decoherence time is close to the maximal possible value since the decoherence is dominated by population relaxation processes. The measured data are in good agreement with a theoretical model based on Fermi's golden rule.