Many-Body Echo

TL;DR

This paper introduces a 'many-body echo' protocol to reverse quantum many-body dynamics in a Bose condensate, demonstrating a more effective method than previous experiments by leveraging phase manipulation during periodic modulation.

Contribution

The paper proposes a novel many-body echo protocol that effectively reverses quantum dynamics in a periodically driven Bose condensate, highlighting the role of micro-motion in Floquet systems.

Findings

Nearly all excited quasi-particles are absorbed back into the condensate after the echo protocol.

The protocol outperforms previous methods in reversing many-body processes.

The scheme can be generalized to other periodically driven many-body systems.

Abstract

In this letter we propose a protocol to reverse a quantum many-body dynamical process. We name it "many-body echo" because the underlying physics is closely related to the spin echo effect in nuclear magnetic resonance systems. We consider a periodical modulation of the interaction strength in a weakly interacting Bose condensate, which resonantly excites quasi-particles from the condensate. A dramatic phenomenon is that, after pausing the interaction modulation for half a period and then continuing on with the same modulation, nearly all the excited quasi-particles in the resonance modes will be absorbed back into the condensate. During the intermediate half period, the free evolution introduces a $\pi$ phase, which plays a role reminiscent of that played by the $\pi$-pulse in the spin echo. Comparing our protocol with another one implemented by the Chicago group in a recent experiment, we find that ours is more effective at reversing the many-body process. The difference between these two schemes manifests the physical effect of the micro-motion in the Floquet theory. Our scheme can be generalised to other periodically driven many-body systems.