Few-photon all-optical phase rotation in a quantum-well micropillar cavity

TL;DR

This paper demonstrates that exciton-polaritons in quantum-well micropillar cavities can produce measurable cross-phase modulation at the single-photon level, advancing scalable quantum photonic technologies.

Contribution

It introduces a method to achieve strong nonlinear phase shifts using exciton-polaritons in micropillars, enabling scalable quantum photonic interactions.

Findings

Observed XPM up to 3 ± 1 mrad per particle at low photon numbers

Showed exciton-polaritons can provide necessary nonlinearity for quantum photonics

Lay the groundwork for quantum information processing in polaritonic lattices

Abstract

Photonic platforms are an excellent setting for quantum technologies because weak photon-environment coupling ensures long coherence times. The second key ingredient for quantum photonics is interactions between photons, which can be provided by optical nonlinearities in the form of cross-phase-modulation (XPM). This approach underpins many proposed applications in quantum optics and information processing, but achieving its potential requires strong single-photon-level nonlinear phase shifts and also scalable nonlinear elements. In this work we show that the required nonlinearity can be provided by exciton-polaritons in micropillars with embedded quantum wells. These combine the strong interactions of excitons with the scalability of micrometer-sized emitters. We observe XPM up to $3 \pm 1$ mrad per particle using laser beams attenuated to below single photon average intensity. With our work serving as a first stepping stone, we lay down a route for quantum information processing in polaritonic lattices.