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arXiv:2509.13094 · Physical Review Research

Steady-state entanglement of spin qubits mediated by nonreciprocal and chiral magnons

Martijn Dols, Mikhail A. Cherkasskii, Victor A. S. V. Bittencourt, Carlos Gonzalez-Ballestero, Durga Bhaktavatsala Rao Dasari, Silvia Viola Kusminskiy

Published May 21, 2026• 1 citation
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Abstract

We propose a hybrid quantum system in which a magnet supporting nonreciprocal magnons, chiral magnons, or both mediates the dissipative and unidirectional coupling of spin qubits. By driving the qubits, the steady state of this qubit-qubit coupling scheme becomes the maximally entangled Bell state. We devise a protocol where the system converges to this entangled state and benchmark it including qubit decay and dephasing. The protocol is numerically tested on a hybrid system consisting of nitrogen-vacancy (NV) centers coupled to magnon surface modes of a yttrium iron garnet (YIG) film. We show that the dephasing time of the NV centers forms the bottleneck for achieving the entanglement of NV centers separated by a distance within the magnon coherence length. Our findings identify the key technological requirements and demonstrate a viable route toward steady-state entanglement of solid-state spins over distances of several microns using magnonic quantum networks, expanding the toolbox of magnonics for quantum information purposes.

DOI
10.1103/w358-y2z9

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We propose a hybrid quantum system in which a magnet supporting nonreciprocal magnons, chiral magnons, or both mediates the dissipative and unidirectional coupling of spin qubits. By driving the qubits, the steady state of this qubit-qubit coupling scheme becomes the maximally entangled Bell state. We devise a protocol where the system converges to this entangled state and benchmark it including qubit decay and dephasing. The protocol is numerically tested on a hybrid system consisting of nitrogen-vacancy (NV) centers coupled to magnon surface modes of a yttrium iron garnet (YIG) film. We show that the dephasing time of the NV centers forms the bottleneck for achieving the entanglement of NV centers separated by a distance within the magnon coherence length. Our findings identify the key technological requirements and demonstrate a viable route toward steady-state entanglement of solid-state spins over distances of several microns using magnonic quantum networks, expanding the toolbox of magnonics for quantum information purposes.
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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.
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