Chiral Spontaneous Photon-Pair Generation with Plasmonic Bound States in the Continuum

TL;DR

This paper introduces a chiral plasmonic metasurface leveraging a quasi-bound state in the continuum to significantly enhance SPDC photon generation efficiency and produce circularly polarized entangled photon pairs at room temperature.

Contribution

It presents a novel ultrathin metasurface design that enables efficient, chiral, room-temperature quantum light sources with potential applications in quantum computing and communications.

Findings

Enhanced SPDC efficiency via qBIC resonance

Generation of circularly polarized entangled photon pairs

Room-temperature operation of the metasurface

Abstract

Spontaneous parametric down conversion (SPDC) has proven to be a robust and prominent method for creating non-classical light sources of entangled single-photon pairs. However, such sources suffer from low efficiency due to the inherent weakness of the SPDC process. Moreover, there is no control of polarization in the generated photons. Circular polarized SPDC-based sources with efficient chiral response are currently missing, which severely precludes the realization of a wide range of practical applications in quantum computing and communications. The current work solves these inherent problems by demonstrating a novel chiral plasmonic metasurface that leverages a strong quasi-bound state in the continuum (qBIC) resonance which significantly increases the SPDC photon generation efficiency and realizes circular polarized (chiral) single-photon pairs. The presented metasurface design is ultrathin, supports efficient free space outcoupling of chiral classical and quantum radiation, and operates at room temperature. Hence, it offers the potential to realize a compact and integrable quantum source of circularly polarized entangled single-photon pairs.