Quantum information dynamics in a high-dimensional parity-time-symmetric system

TL;DR

This paper demonstrates the simulation of quantum information dynamics in a four-dimensional parity-time-symmetric system using single-photon interferometry, revealing complex entropy behaviors across exceptional points.

Contribution

It introduces a scalable experimental approach to study high-dimensional $ ext{PT}$-symmetric quantum systems and explores their entropy dynamics near exceptional points.

Findings

Observation of entropy dynamics in $ ext{PT}$-symmetric quantum systems

Simulation of a four-dimensional $ ext{PT}$-symmetric system across a fourth-order EP

Scalable setup applicable to higher-dimensional systems

Abstract

Non-Hermitian systems with parity-time ($\mathcal{PT}$) symmetry give rise to exceptional points (EPs) with exceptional properties that arise due to the coalescence of eigenvectors. Such systems have been extensively explored in the classical domain, where second or higher order EPs have been proposed or realized. In contrast, quantum information studies of $\mathcal{PT}$-symmetric systems have been confined to systems with a two-dimensional Hilbert space. Here by using a single-photon interferometry setup, we simulate quantum dynamics of a four-dimensional $\mathcal{PT}$-symmetric system across a fourth-order exceptional point. By tracking the coherent, non-unitary evolution of the density matrix of the system in $\mathcal{PT}$-symmetry unbroken and broken regions, we observe the entropy dynamics for both the entire system, and the gain and loss subsystems. Our setup is scalable to the higher-dimensional $\mathcal{PT}$-symmetric systems, and our results point towards the rich dynamics and critical properties.