Transform-limited single photons from a single quantum dot

TL;DR

This paper demonstrates that by controlling optical excitation, it is possible to achieve transform-limited linewidths in single photons emitted from a quantum dot, overcoming decoherence effects caused by nuclear spin noise.

Contribution

The study reveals the dependence of nuclear spin noise on optical excitation and identifies regimes where transform-limited linewidths are achieved in quantum dot emissions.

Findings

Nuclear spin noise varies with resonant laser power.

Transform-limited linewidths are achievable even with slow measurements.

Control of optical excitation regimes improves photon source quality.

Abstract

A semiconductor quantum dot mimics a two-level atom. Performance as a single photon source is limited by decoherence and dephasing of the optical transition. Even with high quality material at low temperature, the optical linewidths are a factor of two larger than the transform-limit. A major contributor to the inhomogeneous linewdith is the nuclear spin noise. We show here that the nuclear spin noise depends on optical excitation, increasing (decreasing) with increasing resonant laser power for the neutral (charged) exciton. Based on this observation, we discover regimes where we demonstrate transform-limited linewidths on both neutral and charged excitons even when the measurement is performed very slowly.