Phonons are considered to be universal quantum transducers due to their ability to couple to a wide variety of quantum systems. Among these systems, solid-state point defect spins are known for being long-lived optically accessible quantum memories. Recently, it has been shown that inversionsymmetric defects in diamond, such as the negatively charged silicon vacancy center (SiV), feature spin qubits that are highly susceptible to strain. Here, we leverage this strain response to achieve coherent and low-power acoustic control of a single SiV spin, and perform acoustically driven Ramsey interferometry of a single spin. Our results demonstrate a novel and efficient method of spin control for these systems, offering a path towards strong spin-phonon coupling and phonon-mediated hybrid quantum systems.

Photon-mediated coupling between distant matter qubits [1,2] may enable secure communication over long distances, the implementation of distributed quantum computing schemes, and the exploration of new regimes of many-body quantum dynamics [3,4]. Solidstate quantum emitters coupled to nanophotonic devices represent a promising approach towards these goals, as they combine strong light-matter interaction and high photon collection efficiencies [5-7]. However, nanostructured environments introduce mismatch and diffusion in optical transition frequencies of emitters, making reliable photon-mediated entanglement generation infeasible [7]. Here we address this long-standing challenge by employing silicon-vacancy (SiV) color centers embedded in electromechanically deflectable nanophotonic waveguides. This electromechanical strain control enables control and stabilization of optical resonance between two SiV centers on the hour timescale.Using this platform, we observe the signature of an entangled, superradiant state arising from quantum interference between two spatially separated emitters in a waveguide. This demonstration and the developed platform constitute a crucial step towards a scalable quantum network with solid state quantum emitters.

We report on the fabrication and characterization of a Fabry-Perot microcavity enclosing a thin diamond membrane at cryogenic temperatures. The cavity is designed to enhance resonant emission of single nitrogen-vacancy centers by allowing spectral and spatial tuning while preserving the optical properties observed in bulk diamond. We demonstrate cavity finesse at cryogenic temperatures within the range of F=4000–12 000 and find a sub-nanometer cavity stability. Modeling shows that coupling nitrogen-vacancy centers to these cavities could lead to an increase in remote entanglement success rates by three orders of magnitude.

In WSe2 monolayers, 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 WSe2 monolayers 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 WSe2 monolayer). 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 WSe2 and demonstrates a route towards exciton traps for exciton condensation.