Nonlinear quantum spectroscopy with Parity-Time symmetric integrated circuits

TL;DR

This paper introduces a quantum nonlinear interferometer with PT symmetry that enhances sensing capabilities by exploiting unique interference effects, enabling efficient detection of analyte-induced losses in integrated photonic circuits.

Contribution

It presents a novel PT-symmetric quantum interferometer design that improves loss sensing and reveals a new fringe shift phenomenon at critical loss levels.

Findings

Identification of a sharp signal fringe shift at critical loss values

Enhanced sensing of analytes through quantum interference effects

Potential for broadband spectroscopy in integrated photonics

Abstract

We propose a novel quantum nonlinear interferometer design that incorporates a passive PT symmetric coupler sandwiched between two nonlinear sections where signal-idler photon pairs are generated. The PT-symmetry enables efficient coupling of the longer-wavelength idler photons and facilitates the sensing of losses in the second waveguide exposed to analyte under investigation, whose absorption can be inferred by measuring only the signal intensity at a shorter wavelength where efficient detectors are readily available. Remarkably, we identify a new phenomenon of sharp signal intensity fringe shift at critical idler loss values, which is distinct from the previously studied PT-symmetry breaking. We discuss how such unconventional properties arising from quantum interference can provide a route to enhancing the sensing of analytes and facilitate broadband spectroscopy applications in integrated photonic platforms.