Entangled photons from the polariton vacuum in a switchable optical cavity

TL;DR

This paper theoretically investigates how entangled photon pairs can be generated from the polariton vacuum in a switchable microcavity system, highlighting the role of rapid coupling changes and mode selection.

Contribution

It introduces a method to generate entangled photons from the polariton vacuum using a fast quench in the ultrastrong coupling regime, with analysis of mode-dependent entanglement.

Findings

Fast coupling quench produces entangled photon pairs.

Entanglement degree depends on photon wave vectors.

Maximally entangled states are achievable through mode selection.

Abstract

We study theoretically the entanglement of two-photon states in the ground state of the intersubband cavity system, the so-called polariton vacuum. The system consists of a sequence of doped quantum wells located inside a microcavity and the photons can interact with intersubband excitations inside the quantum wells. Using an explicit solution for the ground state of the system, operated in the ultrastrong coupling regime, a post-selection is introduced, where only certain two-photon states are considered and analyzed for mode entanglement. We find that a fast quench of the coupling creates entangled photons and that the degree of entanglement depends on the absolute values of the in-plane wave vectors of the photons. Maximally entangled states can be generated by choosing the appropriate modes in the post-selection.