Optimized Dynamical Decoupling Sequences in Protecting Two-Qubit States

TL;DR

This paper investigates the optimization of aperiodic dynamical decoupling sequences for two-qubit systems to enhance decoherence suppression, demonstrating significant improvements over existing nested-UDD sequences under various noise spectra.

Contribution

It introduces a method to optimize DD sequences based on environmental noise spectra for two-qubit states, outperforming universal schemes in most cases.

Findings

Optimized DD sequences outperform nested-UDD in most noise conditions.

Sequences with tens of pulses significantly improve decoherence suppression.

The study provides insights relevant to experimental implementations.

Abstract

Aperiodic dynamical decoupling (DD) sequences of $\pi$ pulses are of great interest to decoherence control and have been recently extended from single-qubit to two-qubit systems. If the environmental noise power spectrum is made available, then one may further optimize aperiodic DD sequences to reach higher efficiency of decoherence suppression than known universal schemes. This possibility is investigated in this work for the protection of two-qubit states, using an exactly solvable pure dephasing model including both local and nonlocal noise. The performance of optimized DD sequences in protecting two-qubit states is compared with that achieved by nested Uhrig's DD (nested-UDD) sequences, for several different types of noise spectrum. Except for cases with noise spectrum decaying slowly in the high-frequency regime, optimized DD sequences with tens of control pulses can perform orders of magnitude better than that of nested-UDD. A two-qubit system with highly unbalanced local noise is also examined to shed more light on a recent experiment. Possible experiments that may be motivated by this work are discussed.