Work

Path integral approach to input-output theory

Year: 2026

Type: article

Abstract: Input-output theory is a well-known tool in quantum optics and ubiquitous in the description of quantum systems probed by light. Owing to the generality of the setup it describes, the theory finds application in a wide variety of experiments in circuit and cavity QED. We present an approach to input-output theory using the Schwinger-Keldysh path integral formalism that gives us direct access to the full output field statistics such as the first- and second-order coherence functions. By making the rich toolbox of nonequilibrium quantum field theory accessible, our formalism greatly simplifies the treatment of nonlinear systems and provides a uniform way of obtaining perturbative results. We showcase this particular strength by computing the output field statistics of a Kerr nonlinear oscillator at finite temperatures through the use of diagrams and diagram summation techniques. We find a reduction in reflection that is not due to photon leakage but rather associated to the squeezing of the output light.

Source: Physical Review Research

DOI: 10.1103/tds9-2tyz

Authors: Aaron Daniel, Matteo Brunelli, Aashish A. Clerk, Patrick P. Potts

Institutions: University of Basel, Centre National de la Recherche Scientifique, Collège de France, Université Paris Sciences et Lettres, University of Chicago

Language: English

Topic: Quantum optics and atomic interactions

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,625