# Photon phase shift at the few-photon level and optical switching by a quantum dot in a microcavity

## TL;DR

This paper demonstrates significant photon phase shifts and a phase switch at the single-photon level using a quantum dot in a microcavity, highlighting potential for quantum information processing.

## Contribution

It introduces a method to achieve near 90-degree photon phase shifts and a photon phase switch using a quantum dot in a micropillar cavity, supported by a theoretical model.

## Key findings

- Photon phase shifts close to 90 degrees achieved
- Demonstration of a photon phase switch via spin-pumping
- Supported by a theoretical model of system dynamics

## Abstract

We exploit the nonlinearity arising from the spin-photon interaction in an InAs quantum dot to demonstrate phase shifts of scattered light pulses at the single-photon level. Photon phase shifts of close to 90 degrees are achieved using a charged quantum dot in a micropillar cavity. We also demonstrate a photon phase switch by using a spin-pumping mechanism through Raman transitions in an in-plane magnetic field. The experimental findings are supported by a theoretical model which explores the dynamics of the system. Our results demonstrate the potential of quantum dot-induced nonlinearities for quantum information processing.