Screening nuclear field fluctuations in quantum dots for indistinguishable photon generation

TL;DR

This paper investigates how nuclear spin fluctuations in quantum dots affect photon indistinguishability and demonstrates a method to screen these fluctuations, enabling high-visibility two-photon interference for quantum photonics.

Contribution

It provides a direct measurement of nuclear spin noise effects on photon spectra and introduces a screening technique to improve photon coherence in quantum dots.

Findings

Nuclear spin fluctuations cause distinguishable Raman photons.

Screening nuclear spin noise restores high-visibility two-photon interference.

Photon coherence is significantly improved after screening.

Abstract

A semiconductor quantum dot can generate highly coherent and indistinguishable single photons. However, intrinsic semiconductor dephasing mechanisms can reduce the visibility of two-photon interference. For an electron in a quantum dot, a fundamental dephasing process is the hyperfine interaction with the nuclear spin bath. Here we directly probe the consequence of the fluctuating nuclear spins on the elastic and inelastic scattered photon spectra from a resident electron in a single dot. We find the nuclear spin fluctuations lead to detuned Raman scattered photons which are distinguishable from both the elastic and incoherent components of the resonance fluorescence. This significantly reduces two-photon interference visibility. However, we demonstrate successful screening of the nuclear spin noise which enables the generation of coherent single photons that exhibit high visibility two-photon interference.