Photonic chiral state transfer near the Liouvillian exceptional point

TL;DR

This paper experimentally investigates the transient chiral state transfer near Liouvillian exceptional points in open quantum systems, revealing the time-dependent nature of chirality and its universal scaling, with implications for simulating open-system dynamics.

Contribution

It demonstrates the first experimental observation of transient chiral state transfer near Liouvillian EPs using single-photon interferometry, highlighting the spectral landscape's role in dynamics.

Findings

Chirality exists only within an intermediate timescale during encircling.

Chirality diminishes at long times as the system relaxes to the steady state.

Universal scaling of chirality with respect to encircling time is observed.

Abstract

As branch-point singularities of non-Hermitian matrices, the exceptional points (EPs) exhibit unique spectral topology and criticality, with intriguing dynamic consequences in non-Hermitian settings. In open quantum systems, EPs also emerge in the Liouvillian spectrum, but their dynamic impact often pertains to the transient dynamics and is challenging to demonstrate. Here, using the flexible control afforded by single-photon interferometry, we study the chiral state transfer when the Liouvillian EP is parametrically encircled. Reconstructing the density-matrix evolution by experimentally simulating the quantum Langevin equation, we show that the chirality of the dynamics is only present within an intermediate encircling timescale and dictated by the landscape of the Liouvillian spectrum near the EP. However, the chirality disappears at long times as the system always relaxes to the steady state. We then demonstrate the universal scaling of the chirality with respect to the encircling time. Our experiment confirms the transient nature of chiral state transfer near a Liouvillian EP in open quantum systems, while our scheme paves the way for simulating general open-system dynamics using single photons.