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arXiv · 2103.07961

Coherence and entanglement of inherently long-lived spin pairs in diamond

H. P. Bartling·M. H. Abobeih·B. Pingault·M. J. Degen·S. J. H. Loenen·C. E. Bradley·J. Randall·M. Markham·D. J. Twitchen·T. H. Taminiau
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Abstract

Understanding and protecting the coherence of individual quantum systems is a central challenge in quantum science and technology. Over the last decades, a rich variety of methods to extend coherence have been developed. A complementary approach is to look for naturally occurring systems that are inherently protected against decoherence. Here, we show that pairs of identical nuclear spins in solids form intrinsically long-lived quantum systems. We study three carbon-13 pairs in diamond and realize high-fidelity measurements of their quantum states using a single NV center in their vicinity. We then reveal that the spin pairs are robust to external perturbations due to a unique combination of three phenomena: a clock transition, a decoherence-free subspace, and a variant on motional narrowing. The resulting inhomogeneous dephasing time is $T_2^* = 1.9(3)$ minutes, the longest reported for individually controlled qubits. Finally, we develop complete control and realize an entangled state between two spin-pair qubits through projective parity measurements. These long-lived qubits are abundantly present in diamond and other solids, and provide new opportunities for quantum sensing, quantum information processing, and quantum networks.

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H. P. Bartling, M. H. Abobeih, B. Pingault, M. J. Degen, S. J. H. Loenen, C. E. Bradley, J. Randall, M. Markham, D. J. Twitchen, T. H. Taminiau. 2021-03-14. Coherence and entanglement of inherently long-lived spin pairs in diamond. https://doi.org/10.1103/physrevx.12.011048

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