Two-photon interference between mutually-detuned resonance fluorescence signals scattered off a semiconductor quantum dot

TL;DR

This study investigates how mutual laser detuning affects photon indistinguishability in resonance fluorescence from a quantum dot, revealing new interference phenomena at larger detunings relevant for quantum computing.

Contribution

It provides the first systematic experimental analysis of detuning effects on photon indistinguishability in quantum dot resonance fluorescence, highlighting anomalous interference features.

Findings

Accurate modeling at small detunings with pure-state theory

Observation of anomalous two-photon interference at larger detunings

Detection of g2_vert(0) < 0.5 indicating non-classical correlations

Abstract

The radiative linewidth of a two-level emitter (TLE) fundamentally limits the bandwidth available for quantum information processing. Despite its importance, no prior experiment has systematically examined how driving detuning affects the indistinguishability of photons scattered from a TLE - a parameter critical for photonic quantum computing. Here, we perform post-selective two-photon interference measurements between mutually detuned resonance fluorescence signals from an InAs quantum dot embedded in a micropillar cavity. At small mutual laser detunings (<=0.5GHz), the results are accurately described by the pure-state model [Nat. Commun. 16, 6453 (2025)], which treats all resonance-fluorescence photons as spontaneous emission. At larger detunings, we uncover an anomalous feature in the two-photon interference, where the normalised second-order correlation function under orthogonal polarisations yields g2_vert(0) < 0.5.