Phase Transitions and Virtual Exceptional Points in Quantum Emitters Coupled to Dissipative Baths

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1. Verfasser: Longhi, Stefano
Format: Preprint
Veröffentlicht: 2025
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author Longhi, Stefano
author_facet Longhi, Stefano
contents Controlling atom-photon interactions in engineered environments is central to quantum optics and emerging quantum technologies. Non-Hermitian (NH) photonic baths, where dissipation fundamentally reshapes spectral and dynamical properties, provide versatile platforms for such control. Here we investigate the relaxation dynamics of a single two-level quantum emitter coupled to the edge of a semi-infinite dissipative bosonic lattice with uniform loss. Despite the simplicity of this bath, we uncover rich dynamical phase transitions, i.e. qualitative changes in spontaneous emission decay as system parameters are varied. In particular, we establish the existence of an optimal dissipative environment for accelerated spontaneous emission. The phase transitions are traced to spectral restructuring of the resolvent, in some cases governed by the coalescence of resonance states on the second Riemann sheet. We identify these coalescences as virtual exceptional points (EPs) of resonance origin, providing a conceptual bridge with EP physics while highlighting distinctive features of infinite-dimensional NH systems. More broadly, our results illustrate how the specific nature of dissipation -- whether uniform losses, staggered losses, or dephasing -- can profoundly impact emitter relaxation, pointing to dissipation engineering as a versatile tool for quantum technologies.
format Preprint
id arxiv_https___arxiv_org_abs_2510_20571
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Phase Transitions and Virtual Exceptional Points in Quantum Emitters Coupled to Dissipative Baths
Longhi, Stefano
Quantum Physics
Optics
Controlling atom-photon interactions in engineered environments is central to quantum optics and emerging quantum technologies. Non-Hermitian (NH) photonic baths, where dissipation fundamentally reshapes spectral and dynamical properties, provide versatile platforms for such control. Here we investigate the relaxation dynamics of a single two-level quantum emitter coupled to the edge of a semi-infinite dissipative bosonic lattice with uniform loss. Despite the simplicity of this bath, we uncover rich dynamical phase transitions, i.e. qualitative changes in spontaneous emission decay as system parameters are varied. In particular, we establish the existence of an optimal dissipative environment for accelerated spontaneous emission. The phase transitions are traced to spectral restructuring of the resolvent, in some cases governed by the coalescence of resonance states on the second Riemann sheet. We identify these coalescences as virtual exceptional points (EPs) of resonance origin, providing a conceptual bridge with EP physics while highlighting distinctive features of infinite-dimensional NH systems. More broadly, our results illustrate how the specific nature of dissipation -- whether uniform losses, staggered losses, or dephasing -- can profoundly impact emitter relaxation, pointing to dissipation engineering as a versatile tool for quantum technologies.
title Phase Transitions and Virtual Exceptional Points in Quantum Emitters Coupled to Dissipative Baths
topic Quantum Physics
Optics
url https://arxiv.org/abs/2510.20571