Realisation of electron-spin-pair qubit in diamond

Realizing quantum networks requires quantum registers next to optically addressable qubits. A variety of

approaches have been reported including recent work on nuclear-spin pairs and single electron spins

surrounding nitrogen-vacancy centers [1, 2]. Here, we investigate a qubit encoded in a pair of electron spins

formed by two P1 centers. We find long inhomogeneous dephasing times of tens of milliseconds, due to a

combination of a decoherence-free subspace and a clock transition. By observing the spin pairs’ temporal

evolution and utilizing RF pulse sequences to address various transitions, we characterize the internal

interactions and resolve the characteristic degrees of freedom of the P1 centers; the Jahn-Teller distortion and

nitrogen state. Using these extra degrees of freedom, we find the P1 centers’ relative position. This work

provides a novel qubit with potential applications in quantum networks and sensing, whilst enriching the

understanding of electronic spin-pair dynamics.

1. Bartling, H. P. et al. Coherence and entanglement of inherently long-lived spin pairs in diamond. arXiv:2103.07961 [quant-ph] (2021).

2. Degen, M. J. et al. Entanglement of dark electron-nuclear spin defects in diamond. Nature Communications 12, 3470 (2021).