Nonlocal qubit interactions are a hallmark of advanced quantum information technologies1,2,3,4,5. The ability to transfer quantum states and generate entanglement over distances much larger than qubit length scales greatly increases connectivity and is an important step towards maximal parallelism and the implementation of two-qubit gates on arbitrary pairs of qubits6. Qubit-coupling schemes based on cavity quantum electrodynamics2,7,8 also offer the possibility of using high-quality-factor resonators as quantum memories3,9. Extending qubit interactions beyond the nearest neighbour is particularly beneficial for spin-based quantum computing architectures, which are limited by short-range exchange interactions10. Despite the rapidly maturing device technology for silicon spin qubits11,12,13,14,15,16, experimental progress towards achieving long-range spin–spin coupling has so far been restricted to interactions between individual spins and microwave photons17,18,19,20. Here we demonstrate resonant microwave-mediated coupling between two electron spins that are physically separated by more than four millimetres. An enhanced vacuum Rabi splitting is observed when both spins are tuned into resonance with the cavity, indicating a coherent interaction between the two spins and a cavity photon. Our results imply that microwave-frequency photons may be used to generate long-range two-qubit gates between spatially separated spins.
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The data that support the findings of this study are available from the corresponding author on reasonable request.
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This work was funded by Army Research Office grant W911NF-15-1-0149 and the Gordon and Betty Moore Foundation’s EPiQS Initiative through grant GBMF4535. The devices were fabricated in the Princeton University Quantum Device Nanofabrication Laboratory. We thank L. Edge, J. Kerckhoff, T. Ladd and E. Pritchett of HRL Laboratories, LLC for providing the 28Si heterostructure used in these experiments, for device simulation support and for technical comments on the manuscript. We acknowledge discussions with M. Benito and G. Burkard.
X.M., J.R.P. and Princeton University have filed a non-provisional patent application related to spin–photon transduction (US patent application number 16534431).
Peer review information Nature thanks Hendrik Bluhm and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Borjans, F., Croot, X.G., Mi, X. et al. Resonant microwave-mediated interactions between distant electron spins. Nature 577, 195–198 (2020). https://doi.org/10.1038/s41586-019-1867-y
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