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arXiv · 2607.02258

A transition-metal qubit in diamond with all-optical control and millisecond quantum memory

I. M. Morris·T. Alberth·L. Crooks·T. Lühmann·D. J. Twitchen·S. Pezzagna·J. Meijer·S. S. Nicley·J. N. Becker
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Abstract

Quantum networks require qubits that combine efficient optical access, coherent control, and long-lived quantum memory, but realizing all three in one scalable platform remains a central bottleneck. Diamond color centers are leading candidates, yet widely studied defects retain tradeoffs among these capabilities. Here, we show that transition-metal defects in diamond provide a distinct route beyond these platforms by combining spin-orbit protected ground-state coherence, all-optical control, and near-infrared emission. Using a single nickel-vacancy (NiV$^-$), we demonstrate an all-optically controlled diamond spin qubit with coherence exceeding one millisecond at 1.65 K, compatible with compact closed-cycle cryogenics. We implement Raman Rabi oscillations and Ramsey interferometry and use all-optical dynamical decoupling to extend coherence from $T_2^*$ = 371 ns to $T_2^{CPMG-4}$ = 1.27 ms, establishing NiV$^-$ as a deployable diamond spin-photon interface.

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I. M. Morris, T. Alberth, L. Crooks, T. Lühmann, D. J. Twitchen, S. Pezzagna, J. Meijer, S. S. Nicley, J. N. Becker. 2026-07-02. A transition-metal qubit in diamond with all-optical control and millisecond quantum memory. https://arxiv.org/abs/2607.02258

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