Preserving entanglement and nonlocality in solid-state qubits by dynamical decoupling

TL;DR

This paper investigates how dynamical decoupling techniques can effectively preserve entanglement and nonlocality in solid-state qubits affected by low-frequency noise, demonstrating improved storage times with specific pulse sequences.

Contribution

It establishes a closed relation between entanglement and nonlocality under pure dephasing, and compares the effectiveness of different dynamical decoupling sequences in protecting quantum correlations.

Findings

Carr-Purcell sequence outperforms others in preserving entanglement.

Entanglement can be stored up to ten times longer with optimized pulse sequences.

Effective entanglement preservation is achievable with current experimental pulse timings.

Abstract

In this paper we study how to preserve entanglement and nonlocality under dephasing produced by classical noise with large low-frequency components, as $1/f$ noise, by Dynamical Decoupling techniques. We first show that quantifiers of entanglement and nonlocality satisfy a closed relation valid for two independent qubits locally coupled to a generic environment under pure dephasing and starting from a general class of initial states. This result allows to assess the efficiency of pulse-based dynamical decoupling for protecting nonlocal quantum correlations between two qubits subject to pure-dephasing local random telegraph and $1/f$-noise. We investigate the efficiency of an "entanglement memory" element under two-pulse echo and under sequences of periodic, Carr-Purcell and Uhrig dynamical decoupling. The Carr-Purcell sequence is shown to outperform the other sequences in preserving entanglement against both random telegraph and $1/f$ noise. For typical $1/f$ flux-noise figures in superconducting nanocircuits, we show that entanglement and its nonlocal features can be efficiently stored up to times one order of magnitude longer than natural entanglement disappearance times employing pulse timings of current experimental reach.