Optimization of partially isolated quantum harmonic oscillator memory systems by mean square decoherence time criteria

TL;DR

This paper investigates optimizing quantum harmonic oscillator memories by maximizing decoherence time through mean square criteria, focusing on partially isolated subsystems to enhance quantum information retention.

Contribution

It introduces a method to extend decoherence times in quantum memories by analyzing partially isolated oscillators and optimizing energy parameters for improved performance.

Findings

Partially isolated subsystems exhibit longer decoherence times.

High-fidelity limits benefit from system decomposition.

Optimization of energy parameters enhances quantum memory stability.

Abstract

This paper is concerned with open quantum harmonic oscillators with position-momentum system variables, whose internal dynamics and interaction with the environment are governed by linear quantum stochastic differential equations. A recently proposed approach to such systems as Heisenberg picture quantum memories exploits their ability to approximately retain initial conditions over a decoherence horizon. Using the quantum memory decoherence time defined previously in terms of a fidelity threshold on a weighted mean-square deviation of the system variables from their initial values, we apply this approach to a partially isolated subsystem of the oscillator, which is not directly affected by the external fields. The partial isolation leads to an appropriate system decomposition and a qualitatively different short-horizon asymptotic behaviour of the deviation, which yields a longer decoherence time in the high-fidelity limit. The resulting approximate decoherence time maximization over the energy parameters for improving the quantum memory performance is discussed for a coherent feedback interconnection of such systems.