Observation of Restored Adiabatic State Transfer in Time-Modulated Non-Hermitian Systems

TL;DR

This paper demonstrates the restoration of truly adiabatic, symmetric state transfer in time-modulated non-Hermitian systems by designing specific parameter trajectories, enabling controlled switching between adiabatic and chiral regimes.

Contribution

It introduces a method to achieve symmetric adiabatic state transfer in non-Hermitian systems, overcoming previous limitations related to complex spectra and non-adiabatic effects.

Findings

Successfully restored adiabatic state transfer in a photonic system.

Achieved controlled switching between symmetric and chiral state transfer regimes.

Demonstrated conditions where the non-Hermitian evolution operator has a real spectrum.

Abstract

Exceptional points (EPs) have attracted extensive research interest due to their intriguing properties. One of the hallmarks of EP physics is that dynamically encircling the EPs induces chiral mode switching, arising from the breakdown of adiabaticity due to the presence of a complex spectrum in the system's Hamiltonian. While such chiral mode behavior has been widely observed experimentally, achieving truly adiabatic, and thus symmetric, state transfer, regardless of the winding direction, in time-modulated non-Hermitian systems has remained elusive. In this work, we demonstrate that this long-sought adiabatic state dynamics can indeed be restored. By steering a two-mode photonic setup along specifically designed trajectories in parameter space, we realize conditions where the associated non-Hermitian evolution operator acquires a purely real spectrum. Moreover, our experimental platform enables controlled switching between symmetric (adiabatic) and chiral (non-adiabatic) state-transfer regimes for the same set of initial modes, thus effectively implementing a universal symmetric-asymmetric two-mode switch. Our results therefore open new avenues for harnessing unique topological spectral properties of non-Hermitian systems, paving the way for the practical design of versatile optical wave-manipulation devices and for advancing both classical and quantum information technologies.