Dephasing and Decorrelation of Spins in a Disordered Environment

TL;DR

This paper investigates how highly disordered environments in the Many-Body Localized phase can suppress spin dephasing, potentially improving quantum coherence by analyzing spin correlations and phase transitions.

Contribution

It demonstrates that disordered environments in the MBL phase can hinder spin dephasing, introducing a robust order parameter and critical exponent for the thermal-MBL transition.

Findings

Dephasing is impeded in the MBL phase.

The spin-spin correlator serves as an effective order parameter.

The critical exponent is robust across system parameters.

Abstract

Dephasing of spins is a major roadblock to scaling up the size of quantum computing systems. We explore the possibility of utilizing highly disordered environments which are in the Many-Body Localized phase to arrest this dephasing. We embedded 2 `special' spins in such a highly disordered environment of Heisenberg spins to act as the target qubits and use the long-time value of the spin-spin correlator $\langle \vec{\sigma}_i \cdot \vec{\sigma}_j\rangle$ as an order parameter to quantify the transition between the thermal and MBL phases of this system. It is seen that the dephasing between spins, as encoded in this correlator, is impeded in a disordered environment when the system is fully localized. The order parameter yields a critical exponent, to characterize the transition between the thermal and MBL phases, that appears to be robust to changes in microscopic parameters of the system or the choice of pair of spins.