Dynamics of the collective modes of an inhomogeneous spin ensemble in a cavity

TL;DR

This paper investigates how inhomogeneously broadened spin ensembles coupled to a cavity evolve over time, revealing that collective excitations can pass through wave number space without dispersion, which is important for quantum memory applications.

Contribution

It introduces a model describing the dynamics of collective spin wave excitations in an inhomogeneous ensemble coupled to a cavity, highlighting wave number evolution without dispersion.

Findings

Collective excitations pass from negative to positive wave numbers without populating the zero mode.

Wave number evolution can be described by a modified time evolution in the presence of cavity coupling.

Results are relevant for multi-mode quantum memories with spin wave encoding.

Abstract

We study the excitation dynamics of an inhomogeneously broadened spin ensemble coupled to a single cavity mode. The collective excitations of the spin ensemble can be described in terms of generalized spin waves and, in the absence of the cavity, the free evolution of the spin ensemble can be described as a drift in the wave number without dispersion. In this article we show that the dynamics in the presence of coupling to the cavity mode can be described solely by a modified time evolution of the wave numbers. In particular, we show that collective excitations with a well- defined wave number pass without dispersion from negative to positive valued wave numbers without populating the zero wave number spin wave mode. The results are relevant for multi-mode collective quantum memories where qubits are encoded in different spin waves.