Signatures of two-photon pulses from a quantum two-level system

TL;DR

This paper investigates the generation of two-photon pulses from a quantum two-level system, revealing oscillations in two-photon emission and their signatures, which could impact multi-photon state production.

Contribution

It provides an intuitive quantum trajectory explanation for two-photon emission oscillations and experimentally observes their signatures in photon bunching.

Findings

Oscillations in two-photon emission are explained by a quantum trajectory approach.

Experimental evidence of photon bunching signatures from a two-level system.

Insights into re-excitation effects impacting single-photon source performance.

Abstract

The theoretical community has found interest in the ability of a two-level atom to generate a strong many-body interaction with light under pulsed excitation. Single-photon generation is the most well-known effect, where a short Gaussian laser pulse is converted into a Lorentzian single-photon wavepacket. However, recent proposals have surprisingly suggested that scattering with intense laser fields off a two-level atom may generate oscillations in two-photon emission that are out of phase with its Rabi oscillations, as the power of the pulse increases. Here, we provide an intuitive explanation for these oscillations using a quantum trajectory approach and show how they may preferentially result in emission of two-photon pulses. Experimentally, we observe signatures of these oscillations by measuring the bunching of photon pulses scattered off a two-level quantum system. Our theory and measurements provide crucial insight into the re-excitation process that plagues on-demand single-photon sources while suggesting the production of novel multi-photon states.