Preservation and destruction of the purity of two-photon states in the interaction with a nanoscatterer

TL;DR

This paper develops a framework to analyze how nanostructures affect the quantum purity of two-photon states, revealing that interactions can cause loss of purity through time delays and frequency shifts.

Contribution

It introduces a new theoretical framework to study the impact of nanostructures on the quantum purity of two-photon states during scattering.

Findings

Purity of incident quantum states can be degraded by nanostructure interactions.

Time delays and frequency shifts explain the loss of quantum purity.

The framework helps understand quantum light interactions with nanoenvironments.

Abstract

The optical resonances supported by nanostructures offer the possibility to enhance the interaction between matter and the quantum states of light. In this work, we provide a framework to study the scattering of quantum states of light with information encoded in their helicity by a nanostructure. We analyze the purity of the scattered output quantum state, and we find that the purity of the incident state can be lost, when it interacts with the optical resonances of the nanostructure. To explain the loss of quantum purity, we develop a physical picture based on time delays and frequency shifts between the output two-photon modes. The framework and analysis proposed in this work establishes a tool to address the interaction between quantum light and nanoenvironments.