High-purity entanglement mediated by magnons despite weak coupling

Abstract:Entangling distant spins via a shared magnonic bus typically faces a tradeoff: stronger spin-magnon coupling increases the entanglement fidelity, but also the spin decay rate. We propose a protocol that breaks this tradeoff. The magnons couple only to a transition outside the computational basis, in which the Bell state is created. Our protocol is probabilistic, and weak coupling reduces the success probability but not the fidelity. We analyze a setup where the spins are two nitrogen-vacancy (NV) centers near a magnetic wire. In the absence of NV dephasing, the protocol reaches unit fidelity with a maximally entangled state, for arbitrarily weak coupling. In our simulations via the Monte-Carlo wavefunction approach, the NV-magnon coupling is taken to be one-third of the magnon linewidth. Considering finite NV dephasing, we predict a fidelity of >0.99 for a state-of-the-art rate, and an optimal fidelity of 0.91 for a moderate rate, both at 0.6% success probability.

Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)

arXiv:2607.19533 [quant-ph]

(or arXiv:2607.19533v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2607.19533 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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