Coherent response of inhomogeneously broadened and spatially localized emitter ensembles in waveguide QED

TL;DR

This paper develops a method to analyze inhomogeneously broadened, spatially localized emitter ensembles in waveguide QED, enabling observation of collective resonances and strong coupling in solid-state quantum systems.

Contribution

It introduces a new approximate analysis method for mesoscopic emitter ensembles in waveguides, demonstrating collective resonances and strong coupling possibilities despite inhomogeneous broadening.

Findings

Collective resonances are observable when linewidth exceeds inhomogeneous line.

Near-unity, tailorable non-Lorentzian extinction of waveguide photons is achievable.

Strong coupling with rare-earth ion ensembles is demonstrated under current experimental restrictions.

Abstract

Spectrally and spatially varying ensembles of emitters embedded into waveguides are ever-present in both well-established and emerging technologies. If control of collective excitations can be attained, a plethora of coherent quantum dynamics and applications may be realized on-chip in the scalable paradigm of waveguide quantum electrodynamics (WQED).Here, we investigate inhomogeneously broadened ensembles embedded with subwavelength spatial extent into waveguides employed as single effective and coherent emitters. We develop a method permitting the approximate analysis and simulation of such mesoscopic systems featuring many emitters, and show how collective resonances are observable within the waveguide transmission spectrum once their linewidth exceeds the inhomogeneous line. In particular, this allows for near-unity and tailorable non-Lorentzian extinction of waveguide photons overcoming large inhomogeneous broadening present in current state-of-the-art. As a particular illustration possible in such existing experiments, we consider the classic emulation of the cavity QED (CQED) paradigm here using ensembles of rare-earth ions as coherent mirrors and qubits and demonstrate the possibility of strong coupling given existing restrictions on inhomogeneous broadening and ensemble spatial extent. This work introduces coherent ensemble dynamics in the solid-state to WQED and extends the realm to spectrally tailorable emitters.