Quantum coherent feedback control with photons

TL;DR

This paper investigates two-photon dynamics in a cavity-QED system with coherent feedback via waveguides, analyzing how feedback schemes influence photon generation and cavity interactions.

Contribution

It introduces a detailed analysis of two-photon processes under continuous and discrete mode coupling schemes in a feedback-controlled cavity-QED system.

Findings

Two-photon states are efficiently generated by tuning waveguide length and coupling strength in continuous mode scheme.

Discrete mode coupling stabilizes Rabi oscillations without notable two-photon states.

Feedback control can tune photon number and dynamics in cavity-QED systems.

Abstract

The purpose of this paper is to study two-photon dynamics induced by the coherent feedback control of a cavity quantum electrodynamics (cavity-QED) system coupled to a waveguide. In this set-up, the two-level system in the cavity can work as a photon source, and the photon emitted into the waveguide can re-interact with the cavity-QED system many times after the transmission and reflection in the waveguide, during which the feedback can tune the number of the photons in and out of the cavity. We analyze the dynamics of two-photon processes in this coherent feedback network in two scenarios: the continuous mode coupling scheme and the discrete periodic mode coupling scheme between the waveguide and cavity. The difference of these coupling schemes is due to their relative scales and the number of semi-transparent mirrors for coupling. Specifically, in the continuous mode coupling scheme, the generation of two-photon states is influenced by the length of the feedback loop by the waveguide and the coupling strength between the waveguide and the cavity-QED system. By tuning the length of the waveguide and the coupling strength, we are able to generate two-photon states efficiently. In the discrete periodic mode coupling scheme, the Rabi oscillation in the cavity can be stabilized and there are no notable two-photon states in the waveguide.