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The negatively charged tin-vacancy center in diamond ( ${\mathrm{SnV}}^{-}$) is an emerging platform for building the next generation of long-distance quantum networks. This is due to the ${\mathrm{SnV}}^{-}$’s favorable optical and spin properties including bright emission, insensitivity to electronic noise, and long spin coherence times at temperatures above 1 K. Here, we demonstrate measurement of a single ${\mathrm{SnV}}^{-}$electronic spin with a single-shot readout fidelity of 87.4%, which can be further improved to 98.5% by conditioning on multiple readouts. In the process, we develop understanding of the relationship between strain, magnetic field, spin readout, and microwave spin control. We show that high-fidelity readout is compatible with rapid microwave spin control, demonstrating a favorable parameter regime for use of the ${\mathrm{SnV}}^{-}$center as a high-quality spin-photon interface. Finally, we use weak quantum measurement to study measurement-induced dephasing; this illuminates the fundamental interplay between measurement and decoherence in quantum mechanics, and provides a universal method to characterize the efficiency of color-center spin readout. Taken together, these results overcome an important hurdle in the development of the ${\mathrm{SnV}}^{-}$-based quantum technologies and, in the process, develop techniques and understanding broadly applicable to the study of solid-state quantum emitters. Published by the American Physical Society2024 

4. Eric L. Peterson, Trond I. Andersen, Giovanni Scuri, Andrew Y. Joe, Andrés M. Mier Valdivia, Xiaoling Liu, Alexander A. Zibrov, Bumho Kim, Takashi Taniguchi, Kenji Watanabe, James Hone, Valentin Walther, Hongkun Park, Philip Kim, Mikhail D. Lukin 

Abstract In WSe₂monolayers, strain has been used to control the energy of excitons, induce funneling, and realize single-photon sources. Here, we developed a technique for probing the dynamics of free excitons in nanoscale strain landscapes in such monolayers. A nanosculpted tapered optical fiber is used to simultaneously generate strain and probe the near-field optical response of WSe₂monolayers at 5 K. When the monolayer is pushed by the fiber, its lowest energy states shift by as much as 390 meV (>20% of the bandgap of a WSe₂monolayer). Polarization and lifetime measurements of these red-shifting peaks indicate they originate from dark excitons. We conclude free dark excitons are funneled to high-strain regions during their long lifetime and are the principal participants in drift and diffusion at cryogenic temperatures. This insight supports proposals on the origin of single-photon sources in WSe₂and demonstrates a route towards exciton traps for exciton condensation.