Spontaneous Emission in a Matter-Wave Open Quantum System

TL;DR

This paper demonstrates matter-wave spontaneous emission in a controlled ultracold atom system, revealing non-Markovian dynamics and tunable bound states, thus emulating quantum electrodynamics phenomena beyond the optical domain.

Contribution

It introduces a novel platform for studying open quantum systems with matter waves, extending decay phenomena known from optics to ultracold atomic systems.

Findings

Observation of exponential and non-Markovian decay dynamics

Detection of tunable bound states with evanescent matter waves

Control over vacuum coupling and excitation energy

Abstract

One of the paradigms of a small quantum system in a dissipative environment is the decay of an excited atom undergoing spontaneous photon emission into the fluctuating quantum electrodynamic vacuum. Recent experiments have demonstrated that the gapped photon dispersion in periodic structures can give rise to novel spontaneous-decay behavior including the formation of dissipative bound states. So far, these effects have been restricted to the optical domain. Here, we experimentally demonstrate similar behavior in a system of artificial atoms in an optical lattice that decay by emitting matter-wave, rather than optical, radiation into free space. By controlling the vacuum coupling and excitation energy, we directly observe exponential and partly reversible, non-Markovian dynamics and detect a tunable bound state containing evanescent matter waves for emission at negative excitation energies. Our system provides a flexible platform for the emulation of open-system quantum electrodynamics and studies of dissipative many-body physics with ultracold atoms.