Quantum jumps in open cavity optomechanics and Liouvillian versus Hamiltonian exceptional points

TL;DR

This paper investigates the nature of exceptional points in cavity optomechanics, distinguishing between Liouvillian and Hamiltonian types, and introduces a hybrid spectral framework to understand their interplay and robustness.

Contribution

It clarifies the differences between Liouvillian and Hamiltonian exceptional points in optomechanics and develops a unified spectral framework using thermofield formalism.

Findings

Liouvillian exceptional points are temperature-independent.

Hamiltonian exceptional points are thermally shifted due to conditional damping.

Exceptional points are robust under small hybrid perturbations.

Abstract

Exceptional points, where two or more eigenstates of a non-Hermitian system coalesce, are now of interest across many fields of physics, from the perspective of open-system dynamics, sensing, nonreciprocal transport, and topological phase transitions. In this work, we investigate exceptional points in cavity optomechanics, a platform of interest to diverse communities working on gravitational-wave detection, macroscopic quantum mechanics, quantum transduction, etc. Specifically, we clarify the role of quantum jumps in making a clear distinction between Liouvillian and Hamiltonian exceptional points in optomechanical systems. While the Liouvillian exceptional point arises from the unconditional Lindblad dynamics and is independent of the phonon-bath temperature, the Hamiltonian exceptional point emerges from the conditional no-jump evolution and acquires a thermal shift due to an enhanced conditional damping. Employing the thermofield formalism, we derive a unified spectral framework that interpolates between these regimes via an analytical hybrid-Liouvillian description. Remarkably, in the weak-quantum-jump regime, the exceptional point is perturbed only at the second order, highlighting the robustness of the Hamiltonian exceptional point under small hybrid perturbations. Our work reveals a continuous family of hybrid exceptional points, clarifies the operational and physical differences between the conditional and unconditional dissipative dynamics in optomechanical systems, and provides a probe for thermal baths.