The Tin-Vacancy Qubit in Diamond—An Emerging Platform for Quantum Technologies

The negatively charged tin-vacancy (SnV) center in diamond is a promising color center qubit for quantum applications. In comparison to other color centers including the more widely known nitrogen-vacancy center in diamond, the SnV has strong photon emission and reduced sensitivity to electrical noise. Furthermore, the SnV has a large spin-orbit coupling which allows for long spin lifetimes at temperatures of several Kelvin, obviating need for millikelvin operation in a dilution refrigerator. These properties make the SnV an excellent candidate for use as a spin/photon interface in quantum networks; future SnV based networks are expected to have much higher entanglement generation rates than the state-of-the-art networks today.<br/><br/>Despite these advantages, the SnV’s large spin-orbit coupling also suppresses the magnetic dipole transition desired for quantum control. These transitions become allowed by strain of the diamond lattice, but there is an associated tradeoff between the performance of microwave spin control and spin readout as functions of strain and the vector orientation of an external magnetic field.<br/><br/>We understand this tradeoff to show [1] high-fidelity microwave spin control, where we demonstrate 99.5% pi-pulse fidelity using 50 ns microwave pulses. With this control, we demonstrate a spin coherence time of up to 0.65 ms measured at 1.7 Kelvin, using a dynamical decoupling sequence of 16 pi-pulses. Furthermore, we show [2] that rapid microwave spin control is compatible with single-shot spin readout. We demonstrate a readout fidelity of 87.4%, limited by low collection total collection efficiency. Finally, we introduce a technique based on weak quantum measurement to precisely measure this efficiency.<br/><br/>Overall, these results solve important outstanding problems in the understanding of the SnV qubit and demonstrate its use as a platform for quantum networks. Future work for the platform includes the combination of nanophotonic integration with spin-control and single-shot spin readout, and the application of such devices to multi-node networks.<br/><br/>[1] Rosenthal <i>et al., </i>Phys. Rev. X <b>13</b>, 031022 (2023)<br/>[2] Rosenthal & Biswas <i>et al., </i>arXiv:2403.13110 (2024)