Interference of interacting matter waves

TL;DR

This paper demonstrates the direct observation and control of matter wave interference driven by interparticle interactions in a Bose-Einstein condensate, revealing interaction-induced phase shifts and coherence effects.

Contribution

It presents the first direct visualization and manipulation of interaction-driven interference patterns in a many-body quantum system.

Findings

Interaction causes measurable phase shifts in matter wave interference.

Control techniques can inhibit dephasing and refocus matter waves.

Interactions can lead to surprisingly coherent evolution in many-body systems.

Abstract

The phenomenon of matter wave interference lies at the heart of quantum physics. It has been observed in various contexts in the limit of non-interacting particles as a single particle effect. Here we observe and control matter wave interference whose evolution is driven by interparticle interactions. In a multi-path matter wave interferometer, the macroscopic many-body wave function of an interacting atomic Bose-Einstein condensate develops a regular interference pattern, allowing us to detect and directly visualize the effect of interaction-induced phase shifts. We demonstrate control over the phase evolution by inhibiting interaction-induced dephasing and by refocusing a dephased macroscopic matter wave in a spin-echo type experiment. Our results show that interactions in a many-body system lead to a surprisingly coherent evolution, possibly enabling narrow-band and high-brightness matter wave interferometers based on atom lasers.