Dynamical Decoupling on Multi-Qubit SysteMS

Abstract

Decoherence is the process by which a quantum system interacts with its environment and evolves into an arbitrary state, often irreversible nonunitary evolution. This is a major setback for quantum information processing which requires the preservation of coherence in the system for implementation of quantum gates and also for storage of information (quantum memory). Dynamical decoupling is a well known technique to prevent the decoherence of open systems. We study the DD of multiqubit systems. Theory indicates that local control on each qubit (DD pulses at different times on each qubit) should perform better than global control (pulses at the same time). We observe that this is not the case in a two qubit system. We then come up with DD sequences based on the measured noise spectral density of the system and study its performance as compared to standard DD sequences acting locally and globally.