In situ Ramsey Interferometry and Diffraction Echo with an Ultracold Fermi Gas

TL;DR

This paper demonstrates in situ Ramsey interferometry with an ultracold Fermi gas, revealing long coherence times and robustness of matter-wave interference, with potential for precision measurements and quantum control.

Contribution

First observation of Bragg scattering in an ultracold Fermi gas and demonstration of a Ramsey interferometer with long-lived coherence signatures.

Findings

Persistent matter wave coherences observed for over 2 seconds.

Fermions oscillate nearly unperturbed due to Pauli exclusion.

Presence of Rb cloud can perturb the fermionic coherence.

Abstract

We report on the first observation of Bragg scattering of an ultracold $^6$Li Fermi gas. We demonstrate a Ramsey-type matter-wave interferometer based on Bragg diffraction and find robust signatures of persistent matter wave coherences using an echo pulse sequence. Because of the Pauli principle, the diffracted fermions oscillate nearly unperturbed in the trapping potential for long times beyond 2 s. This suggests extremely long coherence times. On these timescales, only the presence of a $^{87}$Rb cloud seems sufficient to induce noticeable perturbations.