Suppression of Decoherence and Disentanglement by the Exchange Interaction

TL;DR

This paper investigates how exchange interactions between qubits can suppress decoherence and disentanglement caused by noise, showing that certain entangled states are better protected and more suitable for quantum information storage.

Contribution

It demonstrates that exchange interactions can mitigate noise effects on entangled qubits, especially for Bell states, and analyzes the impact of different noise types on this suppression.

Findings

Exchange interaction suppresses decoherence for Bell states.

Non-Markovian noise enhances the suppression effect.

Singlet-triplet states are better protected than triplet-triplet states.

Abstract

Entangled qubit pairs can serve as a quantum memory or as a resource for quantum communication. The utility of such pairs is measured by how long they take to disentangle or decohere. To answer the question of whether qubit-qubit interactions can prolong entanglement, we calculate the dissipative dynamics of a pair of qubits coupled via the exchange interaction in the presence of random telegraph noise and $1/f$ noise. We show that for maximally entangled (Bell) states, the exchange interaction generally suppresses decoherence and disentanglement. This suppression is more apparent for random telegraph noise if the noise is non-Markovian, whereas for $1/f$ noise the exchange interaction should be comparable in magnitude to strongest noise source. The entangled singlet-triplet superposition state of 2 qubits ($\psi_{\pm}$ Bell state) can be protected by the interaction, while for the triplet-triplet state ($\phi_{\pm}$ Bell state), it is less effective. Thus the former is more suitable for encoding quantum information.