Two-disk synthesis of coherent quantum passive equalizers for channels with Hamiltonian uncertainty

Abstract

The coherent equalization problem involves designing a quantum system that serves as a mean-square near-optimal filter for a given quantum communication channel. Previous work on coherent equalization has typically assumed that the system parameters are known without uncertainty. In this work, we address the problem of coherent passive equalization with uncertainty in the Hamiltonian. Utilizing an S-procedure method, we remodel the passive quantum system with uncertainty as a scaled closed-loop state-space representation with parameter dependencies. We then propose a two-disk synthesis approach for coherent passive equalizers. Numerical examples based on a single optical cavity system and on two-cavity systems with beam splitters demonstrate the effectiveness of the proposed two-disk synthesis method for coherent equalization of passive quantum systems.