# Input-Output Theory with Quantum Pulses

## TL;DR

This paper develops a formalism for modeling the evolution of quantum light pulses interacting with local quantum systems, enabling analysis of complex phenomena like cavity reflection, atomic emission, and Schrödinger-cat state formation.

## Contribution

It introduces a new input-output theory framework that treats quantum pulses as single modes interacting with local systems, extending previous models to include pulse-based dynamics.

## Key findings

- Analyzed cavity reflection with phase noise.
- Studied stimulated atomic emission by quantum pulses.
- Demonstrated formation of Schrödinger-cat states in cavity QED.

## Abstract

We present a formalism that accounts for the evolution of quantum states of travelling light pulses incident on and emanating from a local quantum scatterer such as an atom or a cavity. We assume non-dispersive asymptotic propagation of the pulses and Markovian coupling of the stationary system to input and output fields. This permits derivation of a cascaded system master equation where the input and output pulses are treated as single oscillator modes that both couple to the local system. As examples of our theory we analyse reflection by an empty cavity with phase noise, stimulated atomic emission by a quantum light pulse, and formation of a Schr\"odinger-cat state by the dispersive interaction of a coherent pulse and a single atom in a cavity.