Bell-state generation for spin qubits via dissipative coupling

TL;DR

This paper proposes a method to generate Bell states between spin qubits through dissipative coupling mediated by a magnetic medium, enabling robust entanglement without coherent interactions.

Contribution

It introduces a formal framework for spin qubit-magnet systems and demonstrates how to achieve long-lived, robust Bell states via dissipative processes and postselection.

Findings

Sizable long-lived entanglement can be established without coherent coupling.

Maximally-entangled Bell states are achievable with proper postselection.

The entanglement dynamics involve a non-Hermitian Hamiltonian with an exceptional point.

Abstract

We theoretically investigate the dynamics of two spin qubits interacting with a magnetic medium. A systematic formal framework for this qubit-magnet hybrid system is developed in terms of the steady-state properties of the magnetic medium. Focusing on the induced dissipative coupling between the spin qubits, we show how a sizable long-lived entanglement can be established via the magnetic environment, in the absence of any coherent coupling. Moreover, we demonstrate that maximally-entangled two-qubit states (Bell states) can be achieved in this scheme when complemented by proper postselection. In this situation, the time evolution of the entanglement is governed by a non-Hermitian Hamiltonian, where dynamical phases are separated by an exceptional point. The resultant Bell state is robust against weak random perturbations and does not require the preparation of a particular initial state. Our study may find applications in quantum information science, quantum spintronics, and for sensing of nonlocal quantum correlations.