Tunable bandwidth and nonlinearities in an atom-photon interface with subradiant states

TL;DR

This paper proposes a tunable atom-photon interface using dipole-dipole interactions between slightly detuned atoms, enabling adjustable bandwidth and nonlinearity for quantum networks.

Contribution

It introduces a novel method to achieve tunable bandwidth and nonlinearities in atom-photon interfaces via dipole-dipole coupling of atomic systems.

Findings

Subradiant mode is optically addressable.

Bandwidth can be widely tuned.

Single-photon nonlinearity is achievable.

Abstract

Optical non-linearities at the single photon level are key features to build efficient photon-photon gates and to implement quantum networks. Such optical non-linearities can be obtained using an ideal two-level system such as a single atom coupled to an optical cavity. While efficient, such atom-photon interface however presents a fixed bandwidth, determined by the spontaneous emission time and thus the spectral width of the cavity-enhanced two-level transition, preventing an efficient transmission to bandwidth-mismatched atomic systems in a single quantum network. In the present work, we propose a tunable atom-photon interface making use of the direct dipole-dipole coupling of two slightly different atomic systems. We show that, when weakly coupled to a cavity mode and directly coupled through dipole-dipole interaction, the subradiant mode of two slightly-detuned atomic systems is optically addressable and presents a widely tunable bandwidth and single-photon nonlinearity.