Characterization and Moment Stability Analysis of Quasilinear Quantum Stochastic Systems with Quadratic Coupling to External Fields

TL;DR

This paper analyzes a class of nonlinear open quantum systems with quadratic coupling, providing exact moment dynamics, stability criteria, and applications to non-Gaussian state generation and quantum control design.

Contribution

It introduces a novel framework for analyzing quasilinear quantum stochastic systems with quadratic coupling, including stability analysis and control applications.

Findings

Exact moment dynamics for quasilinear systems derived

Generalized quadratic stability criterion developed

Applicable to non-Gaussian state generation and quantum control

Abstract

The paper is concerned with open quantum systems whose Heisenberg dynamics are described by quantum stochastic differential equations driven by external boson fields. The system-field coupling operators are assumed to be quadratic polynomials of the system observables, with the latter satisfying canonical commutation relations. In combination with a cubic system Hamiltonian, this leads to a class of quasilinear quantum stochastic systems which retain algebraic closedness in the evolution of mixed moments of the observables. Although such a system is nonlinear and its quantum state is no longer Gaussian, the dynamics of the moments of any order are amenable to exact analysis, including the computation of their steady-state values. In particular, a generalized criterion is developed for quadratic stability of the quasilinear systems. The results of the paper are applicable to the generation of non-Gaussian quantum states with manageable moments and an optimal design of linear quantum controllers for quasilinear quantum plants.