Measurements of the Optical Coherence of the SnV in Nanostructured Diamond

Recently the tin-vacancy (SnV) centre in diamond was demonstrated as a competitive spin-qubit with a spin-coherence time of 0.33ms and MHz Rabi rates [1]. This is particularly promising as these demonstrations were achieved in nanostructured diamonds, without any surface passivation engineering, in standard closed-cycle He cryostats; overcoming the charge instability and phononlimited dephasing at these temperatures inherent to the other major defect centres in diamond: the nitrogen and silicon vacancies respectively.

However, despite this promise, in order to realise quantum-networking applications the intrinsic, optical, coherence of the SnV is yet to be shown through Hong-Ou-Mandel (HOM) spectroscopy. In this work, we report on the excited state coherence of the SnV and show that the T2 = 2T1 limit is easily reached given simple Hahn-Echo rephasing protocols. This result further highlights that the SnV is a promising candidate for quantum-networking applications as the maximum achievable HOM visibility is not intrinsically limited by the excited state. As such, these preliminary results highlight that the SnV is a realistic platform on which to build photonic cluster states, and similar photonics-based quantum resources, for high fidelity, error-tolerant, quantum communication.

[1] Debroux, R., Michaels, C. P., Purser, C. M., Wan, N., Trusheim, M. E., Martínez, J. A., & Atatüre, M. (2021). Quantum control of the tin-vacancy spin qubit in diamond. Physical Review X, 11(4), 041041.