Enhancement of vibrationally assisted energy transfer by proximity to exceptional points, probed by fluorescence-detected vibrational spectroscopy

TL;DR

This study demonstrates that vibrationally assisted energy transfer (VAET) can be significantly enhanced near exceptional points in non-Hermitian quantum systems, using fluorescence-detected vibrational spectroscopy on a trapped-ion emulator.

Contribution

It introduces a non-Hermitian quantum system with a PT-symmetric dimer, characterizes exceptional points, and shows how VAET is enhanced near these points, providing new insights into quantum energy transfer.

Findings

VAET is enhanced near degenerate exceptional points.

Eigenstate coalescence provides a spectral signature for EP detection.

Maximal phonon absorption occurs at the EP, enabling multiple excitations.

Abstract

Emulation of energy transfer processes in natural systems on quantum platforms can further our understanding of complex dynamics in nature. One notable example is the demonstration of vibrationally assisted energy transfer (VAET) on a trapped-ion quantum emulator, which offers insights for the energetics of light harvesting. In this work, we expand the study of VAET simulation with trapped ions to a non-Hermitian quantum system comprising a $\mathscr{PT}$-symmetric chromophore dimer weakly coupled to a vibrational mode. We first characterize exceptional points (EPs) and non- Hermitian features of the excitation energy transfer processes in the absence of the vibration, finding a degenerate pair of second-order EPs. Exploring the non-Hermitian dynamics of the whole system including vibrations, we find that energy transfer accompanied by absorption of phonons from a vibrational mode can be significantly enhanced near such a degenerate EP. Our calculations reveal a unique spectral feature accompanying the coalescing of eigenstates and eigenenergies that provides a novel approach to probe the degenerate EP by fluorescence-detected vibrational spectroscopy. Enhancement of the VAET process near the EP is found to be due to maximal favorability of phonon absorption at the degenerate EP, enabling multiple simultaneous excitations. Our work on improving VAET processes in non-Hermitian quantum systems paves the way for leveraging non-Hermiticity in quantum dynamics related to excitation energy transfer.