An efficient quantum photonic phase shift in a low Q-factor regime

Abstract

Solid-state quantum emitters have long been recognised as the ideal platform to realize integrated quantum photonic technologies. We demonstrate that a self-assembled negatively charged quantum dot (QD) in a low Q-factor photonic micropillar is a suitable design for deterministic polarisation switching and spin-photon entanglement. We show this by measuring a shift in phase of an input single photon of at least 2π/3. As we explain in the text, this is strong experimental proof that input photons can interact with the emitter deterministically. A deterministic photon-emitter interaction is a viable and scalable means to achieve several vital functionalities such as single photon switches and entanglement gates. Our experimentally determined value is limited by mode mismatch between the input laser and the cavity, QD spectral fluctuations and spin relaxation. When on-resonance we estimate that up to ∼80% of the collected photons couple into the cavity mode and have interacted with the QD and undergone a phase shift of π.