Overview of Quantum Memory Protection and Adiabaticity Induction by Fast-Signal Control

TL;DR

This paper reviews how fast-signal control protocols, including dynamical decoupling, effectively protect quantum memory from decoherence and leakage, regardless of pulse sequence details, by analyzing various dynamical equations.

Contribution

It provides a comprehensive analysis of fast-signal control in quantum memory protection, emphasizing its robustness against different pulse configurations and noise types.

Findings

Fast-signal control suppresses decoherence and leakage effectively.

Protection quality is insensitive to pulse sequence configurations.

Control effectiveness depends on shifting the system beyond bath cutoff frequency.

Abstract

A quantum memory or information processing device is subject to disturbance from its surrounding environment or inevitable leakage due to its contact with other systems. To tackle these problems, several control protocols have been proposed for quantum memory or storage. Among them, the fast-signal control or dynamical decoupling based on external pulse sequences provides a prevailing strategy aimed at suppressing decoherence and preventing the target systems from the leakage or diffusion process. In this paper, we review the applications of this protocol in protecting quantum memory under the non-Markovian dissipative noise and maintaining systems on finite speed adiabatic passages without leakage there-from. We analyze leakage and control perturbative and nonperturbative dynamical equations including second-order master equation, quantum-state-diffusion equation, and one-component master equation derived from Feshbach PQ-partitioning technique. It turns out that the quality of fast-modulated signal control is insensitive to configurations of the applied pulse sequences. Specifically, decoherence and leakage will be greatly suppressed as long as the control sequence is able to effectively shift the system beyond the bath cutoff frequency, almost independent of the details of the control sequences which could be ideal pulses, regular rectangular pulses, random pulses and even noisy pulses.