Universal Dynamical Decoupling: Two-Qubit States and Beyond

TL;DR

This paper extends Uhrig's dynamical decoupling sequence from single-qubit to two-qubit and multi-level systems, enabling efficient preservation of quantum coherence and entanglement with fewer pulses.

Contribution

It introduces a method to adapt Uhrig's pulse sequence for multi-qubit and multi-level systems, enhancing decoherence suppression and entanglement preservation.

Findings

Uhrig's sequence can preserve quantum coherence in two-qubit systems.

The method requires only N pulses for order $1+O(T^{N+1})$ accuracy.

The scheme efficiently locks two-qubit entangled states.

Abstract

Uhrig's dynamical decoupling pulse sequence has emerged as one universal and highly promising approach to decoherence suppression. So far both the theoretical and experimental studies have examined single-qubit decoherence only. This work extends Uhrig's universal dynamical decoupling from one-qubit to two-qubit systems and even to general multi-level quantum systems. In particular, we show that by designing appropriate control Hamiltonians for a two-qubit or a multi-level system, Uhrig's pulse sequence can also preserve a generalized quantum coherence measure to the order of $1+O(T^{N+1})$, with only $N$ pulses. Our results lead to a very useful scheme for efficiently locking two-qubit entangled states. Future important applications of Uhrig's pulse sequence in preserving the quantum coherence of multi-level quantum systems can also be anticipated.