Nature - USA (2019-07-18)

Letter reSeArCH

15. Yoneda, J. et al. A quantum-dot spin qubit with coherence limited by charge
    noise and fidelity higher than 99.9%. Nat. Nanotechnol. 13 , 102–106 (2018).


16. Dial, O. E. et al. Charge noise spectroscopy using coherent exchange oscillations
    in a singlet-triplet qubit. Phys. Rev. Lett. 110 , 146804 (2013).


17. Nowack, K. C. et al. Single-shot correlations and two-qubit gate of solid-state
    spins. Science 333 , 1269–1272 (2011).


18. Broome, M. A. et al. High-fidelity single-shot singlet-triplet readout of
    precision-placed donors in silicon. Phys. Rev. Lett. 119 , 046802 (2017).


19. Broome, M. A. et al. Two-electron spin correlations in precision placed donors in
    silicon. Nat. Commun. 9 , 980 (2018).


20. Hsueh, Y.-L. et al. Spin-lattice relaxation times of single donors and donor
    clusters in silicon. Phys. Rev. Lett. 113 , 246406 (2014).


21. Koiller, B., Hu, X. & Das Sarma, S. Exchange in silicon-based quantum computer
    architecture. Phys. Rev. Lett. 88 , 027903 (2001).


22. Wang, Y. et al. Highly tunable exchange in donor qubits in silicon. npj Quantum
    Inf. 2 , 16008 (2016).


23. Wang, Y., Chen, C.-Y., Klimeck, G., Simmons, M. Y. & Rahman, R. Characterizing
    Si:P quantum dot qubits with spin resonance techniques. Sci. Rep. 6 , 31830
    (2016); corrigendum 6 , 38120 (2016).


24. Watson, T. F., Weber, B., House, M. G., Büch, H. & Simmons, M. Y. High-fidelity
    rapid initialization and read-out of an electron spin via the single donor
    D− charge state. Phys. Rev. Lett. 115 , 166806 (2015).


25. Watson, T. F. et al. Atomically engineered electron spin lifetimes of 30 s in
    silicon. Sci. Adv. 3 , e1602811 (2017).


26. Politi, A., Cryan, M. J., Rarity, J. G., Yu, S. & O’Brien, J. L. Silica-on-silicon
    waveguide quantum circuits. Science 320 , 646–649 (2008).


27. Abrosimov, N. V. et al. A new generation of 99.999% enriched 28Si single crystals
    for the determination of Avogadro’s constant. Metrologia 54 , 599–609 (2017).


28. Throckmorton, R. E., Barnes, E. & Das Sarma, S. Environmental noise effects on
    entanglement fidelity of exchange-coupled semiconductor spin qubits. Phys.
    Rev. B 95 , 085405 (2017).


29. Martins, F. et al. Noise suppression using symmetric exchange gates in spin
    qubits. Phys. Rev. Lett. 116 , 116801 (2016).


30. Wang, X. et al. Composite pulses for robust universal control of singlet–triplet
    qubits. Nat. Commun. 3 , 997 (2012).


31. Horibe, K., Kodera, T. & Oda, S. Back-action-induced excitation of electrons in a
    silicon quantum dot with a single-electron transistor charge sensor. Appl. Phys.
    Lett. 106 , 053119 (2015).
    32. Shamim, S., Weber, B., Thompson, D. W., Simmons, M. Y. & Ghosh, A. Ultra
    low-noise atomic-scale structures for quantum circuitry in silicon. Nano Lett. 16 ,
    5779–5784 (2016).
    33. Keizer, J. G., Koelling, S., Koenraad, P. M. & Simmons, M. Y. Suppressing
    segregation in highly phosphorus doped silicon monolayers. ACS Nano 9 ,
    12537–12541 (2015).

Acknowledgements The research was supported by the Australian Research

Council Centre of Excellence for Quantum Computation and Communication

Technology (project number CE170100012), the US Army Research Office

under contract number W911NF-17-1-0202 and Silicon Quantum Computing

Pty Ltd. M.Y.S. acknowledges an Australian Research Council Laureate

Fellowship. This work was performed in part at the NSW node of the Australian

National Fabrication Facility.

Reviewer information Nature thanks Benjamin D’Anjou and the other

anonymous reviewer(s) for their contribution to the peer review of this work.

Author contributions Y.H., S.K.G. and L.K. fabricated the device. Y.H., S.K.G. and

D.K. performed the measurements. Y.H., S.K.G., D.K, L.K. and J.G.K. analysed the

data. The manuscript was written by Y.H., S.K.G. and M.Y.S. with input from all

other authors. M.Y.S. conceived and supervised the project.

Competing interests M.Y.S. is a director of the company Silicon Quantum

Computing Pty Ltd.

Additional information

Extended data is available for this paper at https://doi.org/10.1038/s41586-

019-1381-2.

Supplementary information is available for this paper at https://doi.org/

10.1038/s41586-019-1381-2.

Reprints and permissions information is available at http://www.nature.com/

reprints.

Correspondence and requests for materials should be addressed to M.Y.S.

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional

claims in published maps and institutional affiliations.

© The Author(s), under exclusive licence to Springer Nature Limited 2019

18 JULY 2019 | VOL 571 | NAtUre | 375