A Quantum Extension of the Semiclassical Theory of Electrical Susceptibility

TL;DR

This paper extends the semiclassical theory of electrical susceptibility to include quantized radiation and matter, deriving conditions for validity and predicting phenomena like photon number dependent susceptibility.

Contribution

It introduces a quantum extension of the semiclassical susceptibility theory, enabling analysis of photon number effects and validity conditions.

Findings

Derived expressions for quantum susceptibilities

Predicted photon number dependent susceptibility phenomena

Established conditions for semiclassical approximation validity

Abstract

It is shown here how the semiclassical theory of electrical susceptibility can be extended to the case in which both radiation and matter are quantized. This is done specifically for the cases of linear and second order susceptibilities. The expressions derived allow to determine a set of conditions for the validity of the semiclassical approximation and predict interesting new phenomena such as photon number dependent susceptibility.