Lindblad dynamics of open multi-mode bosonic systems: Algebra of bilinear superoperators, exceptional points and speed of evolution

TL;DR

This paper introduces an algebraic method to analyze the Lindblad dynamics of multi-mode bosonic systems, revealing the structure of exceptional points and the evolution speed, with applications to photonic polarization modes.

Contribution

It develops an algebraic approach using Lie algebra of superoperators to diagonalize the Liouvillian and analyze spectral properties, including exceptional points, in multi-mode bosonic systems.

Findings

Diagonalization of the Liouvillian via algebraic methods

Identification of exceptional points where the matrix is non-diagonalizable

Analysis of the evolution speed in a two-mode photonic system

Abstract

We develop the algebraic method based on the Lie algebra of quadratic combinations of left and right superoperators associated with matrices to study the Lindblad dynamics of multimode bosonic systems coupled a thermal bath and described by the Liouvillian superoperator that takes into account both dynamical (coherent) and environment mediated (incoherent) interactions between the modes. Our algebraic technique is applied to transform the Liouvillian into the diagonalized form by eliminating jump superoperators and solve the spectral problem. The temperature independent effective non-Hermitian Hamiltonian, $\hat{H}_{eff}$, is found to govern both the diagonalized Liouvillian and the spectral properties. It is shown that the Liouvillian exceptional points are represented by the points in the parameter space where the matrix, $H$, associated with $\hat{H}_{eff}$ is non-diagonalizable. We use our method to derive the low-temperature approximation for the superpropagator and to study the special case of a two mode system representing the photonic polarization modes. For this system, we describe the geometry of exceptional points in the space of frequency and relaxation vectors parameterizing the intermode couplings and, for a single-photon state, evaluate the time dependence of the speed of evolution as a function of the angles characterizing the couplings and the initial state.