Induced decoherence and entanglement by interacting quantum spin baths

TL;DR

This paper investigates how interacting quantum spin baths influence decoherence and entanglement in qubits, revealing phase-dependent behaviors and the potential for baths to generate entanglement.

Contribution

It nonperturbatively analyzes the effects of XXZ spin chain baths on qubit dynamics using t-DMRG, extending beyond uniform coupling models.

Findings

Spin baths can induce entanglement in initially disentangled qubits.

In ferromagnetic phases, dynamics show oscillatory behavior due to coupling with the order parameter.

Entanglement sudden death occurs in paramagnetic and antiferromagnetic phases.

Abstract

The reduced dynamics of a single or two qubits coupled to an interacting quantum spin bath modeled by a XXZ spin chain is investigated. By using the method of time-dependent density matrix renormalization group (t-DMRG), we go beyond the uniform coupling central spin model and evaluate nonperturbatively the induced decoherence and entanglement. It is shown that both decoherence and entanglement strongly depend on the phase of the underlying spin bath. We show that in general, spin baths can induce entanglement for an initially disentangled pair of qubits. Furthermore, when the spin bath is in the ferromagnetic phase, because qubits directly couple to the order parameter, the reduced dynamics shows oscillatory type behavior. On the other hand, only for paramagnetic and antiferromagnetic phases, initially entangled states suffer from the entanglement sudden death. By calculating concurrence, the finite disentanglement time is mapped out for all phases in the phase diagram of the spin bath.