Exceptional points in oligomer chains

TL;DR

This paper develops a quantum theory for chains of coupled modes to explore exceptional points and parity-time symmetry, revealing their effects on quantum transport, correlations, and how they evolve with chain length and parity.

Contribution

It introduces a quantum framework for non-Hermitian physics in oligomer chains, analyzing exceptional points and symmetry phases with implications for optics and quantum transport.

Findings

Exceptional points govern parity-time symmetry in quantum chains

Locations of exceptional points depend on chain length and parity

Transitions between symmetric phases affect light transport and coherence

Abstract

Symmetry underpins our understanding of physical law. Open systems, those in contact with their environment, can provide a platform to explore parity-time symmetry. While classical parity-time symmetric systems have received a lot of attention, especially because of the associated advances in the generation and control of light, there is much more to be discovered about their quantum counterparts. Here we provide a quantum theory which describes the non-Hermitian physics of chains of coupled modes, which has applications across optics and photonics. We elucidate the origin of the exceptional points which govern the parity-time symmetry, survey their signatures in quantum transport, study their influence for correlations, and account for long-range interactions. We also find how the locations of the exceptional points evolve as a function of the chain length and chain parity, capturing how an arbitrary oligomer chain transitions from its unbroken to broken symmetric phase. Our general results provide perspectives for the experimental detection of parity-time symmetric phases in one-dimensional arrays of quantum objects, with consequences for light transport and its degree of coherence.