A promising application for solid-state qubits in semiconductor hosts is the development of processing nodes in a quantum network. Quantum information is locally manipulated within the solid-state qubit and, once encoded onto photons, is then communicated over remote distances. In silicon carbide, divacancies have shown excellent spin properties, including single-spin addressability, long spin coherence times, and a simple off-resonant initialization and readout procedure. Optically, the divacancy’s fluorescence lies in the near-infrared and is highly compatible with low-loss optical fibers, widely used in existing telecommunications infrastructure. Recent work has demonstrated that the divacancy possesses a high-fidelity spin-to-photon interface, unifying the strengths of the defect’s spin and optical properties, and opening the door for advanced quantum optics experiments with the divacancy.

We use resonant spectroscopy to elucidate the divacancy’s excited state fine structure, enabled by recent advances in silicon carbide material quality. Six spectroscopic lines (above, left) arise under simultaneous microwave and resonant optical excitation, demonstrating an excited state structure similar to that of the NV-center in diamond. Sharp, highly spin-dependent transitions between the ground-state and excited-state orbitals produce high-fidelity optical interfaces for both spin state initialization and readout. Spin readout contrast using cycling spin-dependent transitions has exceeded 94%, as seen in Rabi oscillations employing resonant readout (above, right), which is a six-fold improvement over the 9%-15% contrast seen with off-resonant excitation.

Many advanced quantum information and quantum communication applications will require a spin-projective optical readout mechanism, which involves probing a spin-dependent transition and extracting the maximal number of photons while minimally disturbing the spin state. Only a finite number of photons can be extracted from the divacancy before the spin flips and quantum information is lost. The spin’s sensitivity to resonant optical excitation can be summarized by a spin-flip rate, and we observe a divacancy spin-flip rate approaching 100 kHz (below), which is competitive with figures reported in diamond NV-centers.

With these critical advances, the divacancy is an increasingly promising platform for state-of-the-art quantum information and quantum metrology applications, including photon-mediated remote entanglement and quantum teleportation.

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To learn more about our studies, please see:

“Isolated Spin Qubits in SiC with a High-Fidelity Infrared Spin-to-Photon Interface”, D. J. Christle, P. V. Klimov, C. F. de las Casas, K. Szász, V. Ivády, V. Jokubavicius, J. U. Hassan, M. Syväjärvi, W. F. Koehl, T. Ohshima, N. T. Son, E. Janzén, Á. Gali, and D. D. Awschalom, Physical Review X 7, 021046 (2017).