# Control of continuous-mode single-photon states: a review

## TL;DR

This review paper discusses the theory and control of continuous-mode single-photon states, including their generation, manipulation, and measurement, with a focus on linear quantum systems and feedback networks.

## Contribution

It provides a comprehensive overview of the methods for controlling and manipulating continuous-mode single-photon states using linear quantum systems and feedback techniques.

## Key findings

- Linear quantum systems respond predictably to single-photon inputs
- Coherent feedback networks can shape photon pulse profiles
- Photon addition and subtraction can generate Schrödinger cat states

## Abstract

In this survey, we first introduce quantum fields and open quantum systems, then we present continuous-mode single-photon states and discuss discrete measurements of a single-photon field. After that, we introduce linear quantum systems and show how a linear quantum system responds to a single-photon input. Then we investigate how a coherent feedback network can be used to manipulate the temporal pulse shape of a single-photon state. Afterwards, we present single-photon filter and master equations. Finally, we discuss the generation of Schr\"odinger cat states by means of photon addition and subtraction