# Entanglement and control of single nuclear spins in isotopically engineered silicon carbide

## Abstract

Nuclear spins in the solid state are both a cause of decoherence and a valuable resource for spin qubits. In this work, we demonstrate control of isolated 29Si nuclear spins in silicon carbide (SiC) to create an entangled state between an optically active divacancy spin and a strongly coupled nuclear register. We then show how isotopic engineering of SiC unlocks control of single weakly coupled nuclear spins and present an ab initio method to predict the optimal isotopic fraction that maximizes the number of usable nuclear memories. We bolster these results by reporting high-fidelity electron spin control (F = 99.984(1)%), alongside extended coherence times (Hahn-echo T2 = 2.3 ms, dynamical decoupling T2DD > 14.5 ms), and a >40-fold increase in Ramsey spin dephasing time (T2*) from isotopic purification. Overall, this work underlines the importance of controlling the nuclear environment in solid-state systems and links single photon emitters with nuclear registers in an industrially scalable material.

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## Data availability

The source data of the figures in this manuscript can be accessed from the Zenodo repository62.

## Code availability

The codes associated with this manuscript are available from the corresponding author upon request.

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## Acknowledgements

We thank E. O. Glen, S. Bayliss, G. Wolfowicz and P. J. Duda for useful discussions and assistance. We thank Quantum Opus for their assistance with detectors. This work made use of the UChicago MRSEC (NSF DMR-1420709) and Pritzker Nanofabrication Facility, which receives support from the SHyNE, a node of the NSF’s National Nanotechnology Coordinated Infrastructure (NSF ECCS-1542205). C.P.A., A.B., K.C.M., A.L.C. and D.D.A. were supported by grant nos. AFOSR FA9550-19-1-0358, DARPA D18AC00015KK1932 and ONR N00014-17-1-3026. T.O. was supported by KAKENHI (grant nos. 18H03770 and 20H00355). J.U.H was supported by the Swedish Energy Agency (grant no. 43611-1). N.T.S. was supported by the Swedish Research Council (grant no. VR 2016-04068) and the Carl Tryggers Stiftelse för Vetenskaplig Forskning (grant no. CTS 15:339). J.U.H. and N.T.S. were also supported by the EU H2020 project QuanTELCO (grant no. 862721) and the Knut and Alice Wallenberg Foundation (grant no. KAW 2018.0071).

## Author information

Authors

### Contributions

A.B. and C.P.A. conceived the experiments, performed the measurements and analysed the data. C.P.A. fabricated the devices. A.B. and K.C.M developed the experimental setup. M.O., H.M. and G.G. provided a theoretical framework. M.O. performed the numerical simulations and computations. A.L.C. assisted in device fabrication. H.A. and T.O. performed the electron irradiation. J.U.H. and N.T.S. grew the isotopically purified SiC samples. D.D.A. advised on all efforts. All authors contributed to manuscript preparation.

### Corresponding author

Correspondence to David D. Awschalom.

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### Competing interests

The authors declare no competing interests.

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## Supplementary information

### Supplementary Information

Supplementary Figs. 1–21 and discussion.

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Bourassa, A., Anderson, C.P., Miao, K.C. et al. Entanglement and control of single nuclear spins in isotopically engineered silicon carbide. Nat. Mater. (2020). https://doi.org/10.1038/s41563-020-00802-6