Echo spectroscopy of bulk Bogoliubov excitations in trapped Bose-Einstein condensates

TL;DR

This paper introduces an echo technique to narrow the linewidth of Bogoliubov excitations in trapped Bose-Einstein condensates, improving measurement precision by reducing inhomogeneous broadening through a double two-photon Bragg process and a four-photon implementation.

Contribution

It presents a novel echo method for reducing inhomogeneous broadening of excitations in BECs, including theoretical calculations and experimental demonstration.

Findings

Significant reduction in inhomogeneous linewidth achieved.

Enhanced efficiency at low momentum due to many-body effects.

Experimental validation of four-photon echo implementation.

Abstract

We propose and demonstrate an echo method to reduce the inhomogeneous linewidth of Bogoliubov excitations, in a harmonically-trapped Bose-Einstein condensate. Our proposal includes the transfer of excitations with momentum +q to -q using a double two photon Bragg process, in which a substantial reduction of the inhomogeneous broadening is calculated. Furthermore, we predict an enhancement in the method's efficiency for low momentum due to many-body effects. The echo can also be implemented by using a four photon process, as is demonstrated experimentally.