# Synthetic parity-time symmetry breaking in a single microcavity

## TL;DR

This paper demonstrates PT symmetry and its breaking in a single microcavity using nonlinear Brillouin scattering, opening new avenues for non-Hermitian physics in synthetic photonic dimensions.

## Contribution

It introduces a novel method to realize PT symmetry in a synthetic spectral dimension within a single microcavity, combining theory and experiment.

## Key findings

- Observation of PT symmetry breaking in a microcavity
- Implementation of spectral gain and loss via nonlinear Brillouin scattering
- Potential applications in all-optical signal processing and quantum information

## Abstract

Non-Hermitian systems based on parity-time (PT) symmetry reveal rich physics beyond the Hermitian regime. So far, realizations of PT-symmetric systems have been limited to the spatial domain. Here we theoretically and experimentally demonstrate PT symmetry in a synthetic spectral dimension induced by nonlinear Brillouin scattering in a single optical microcavity, where electromagnetically induced transparency or absorption in two spectral resonances provides the optical gain and loss to observe a phase transition between two symmetry regimes. This scheme provides a new paradigm towards the investigation of non-Hermitian physics in a synthetic photonic dimension for all-optical signal processing and quantum information science.

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Source: https://tomesphere.com/paper/1907.03294