Branch-entangled polariton pairs in planar microcavities and photonic wires

TL;DR

This paper proposes a scheme to generate branch-entangled polariton pairs in microcavities and photonic wires, enabling frequency-entangled photon emission with specific phase-matching and loss considerations.

Contribution

It introduces a novel method for creating branch-entangled polariton pairs via spontaneous inter-branch scattering in microcavities and wires, analyzing phase-matching and nonlinear loss effects.

Findings

Branch-entanglement is achievable with two twin processes exchanging signal and idler roles.

Phase-matching conditions are fulfilled for upper polariton branch pumping in planar microcavities.

Protection from the exciton reservoir is crucial for entanglement in photonic wires.

Abstract

A scheme is proposed for the generation of branch-entangled pairs of microcavity polaritons through spontaneous inter-branch parametric scattering. Branch-entanglement is achievable when there are two twin processes, where the role of signal and idler can be exchanged between two different polariton branches. Branch-entanglement of polariton pairs can lead to the emission of frequency-entangled photon pairs out of the microcavity. In planar microcavities, the necessary phase-matching conditions are fulfilled for pumping of the upper polariton branch at an arbitrary in-plane wave-vector. The important role of nonlinear losses due to pair scattering into high-momentum exciton states is evaluated. The results show that the lack of protection of the pump polaritons in the upper branch is critical. In photonic wires, branch-entanglement of one-dimensional polaritons is achievable when the pump excites a lower polariton sub-branch at normal incidence, providing protection from the exciton reservoir.