Sub-shot-noise emission statistics of a CW-excited single photon source

TL;DR

This paper develops a theoretical model showing that continuously excited single-photon sources can exhibit sub-Poissonian, nonclassical emission statistics, challenging the assumption that such sources are inherently Poissonian.

Contribution

The work introduces a stochastic model of a CW-excited two-level single-photon source demonstrating non-Poissonian emission under certain conditions.

Findings

Photon emission can be sub-Poissonian when excitation and decay rates are comparable.

Continuous excitation does not necessarily lead to Poissonian statistics.

Detection inefficiencies and dead time influence the observation of nonclassical light.

Abstract

Shot noise sets a fundamental limit on the sensitivity of classical optical measurements, with coherent emitters achieving the lowest possible shot-noise level. Emission from sub-Poissonian light provides a pathway to surpass this limit, and single-photon sources provide a natural platform for generating such light. However, it is commonly assumed that continuously excited single-photon sources exhibit Poissonian statistics. In this work, a theoretical model of a continuously driven two-level single-photon source is developed, treating both excitation and radiative decay as stochastic processes. The analysis demonstrates that photon emission can display sub-Poissonian statistics when excitation and decay rates are comparable, showing that continuous excitation does not inherently preclude nonclassical emission. The model is further extended to include finite detection efficiency and detector dead time, illustrating how these practical non-idealities can affect the experimental observation of sub-Poissonian statistics.