Phonon limit to simultaneous near-unity efficiency and indistinguishability in semiconductor single photon sources

TL;DR

This paper investigates the fundamental phonon-induced limitations in semiconductor quantum dot single-photon sources, revealing trade-offs between efficiency and indistinguishability due to lattice relaxation effects.

Contribution

It provides a detailed analysis of how lattice relaxation impacts the efficiency and indistinguishability trade-offs in quantum dot sources with waveguide and cavity architectures.

Findings

Waveguide sources exhibit an inverse relationship between efficiency and indistinguishability.

Cavity sources can achieve high efficiency and indistinguishability simultaneously, but with fundamental limits.

Near-unity indistinguishability (>99%) is limited to about 96% efficiency under realistic conditions.

Abstract

Semiconductor quantum dots have recently emerged as a leading platform to efficiently generate highly indistinguishable photons, and this work addresses the timely question of how good these solid-state sources can ultimately be. We establish the crucial role of lattice relaxation in these systems in giving rise to trade-offs between indistinguishability and efficiency. We analyse the two source architectures most commonly employed: a quantum dot embedded in a waveguide and a quantum dot coupled to an optical cavity. For waveguides, we demonstrate that the broadband Purcell effect results in a simple inverse relationship, where indistinguishability and efficiency cannot be simultaneously increased. For cavities, the frequency selectivity of the Purcell enhancement results in a more subtle trade-off, where indistinguishability and efficiency can be simultaneously increased, though by the same mechanism not arbitrarily, limiting a source with near-unity indistinguishability ($>99$\%) to an efficiency of approximately 96\% for realistic parameters.