Abstract

Photonics is a promising platform for implementing universal quantum information processing. Its main challenges include precise control of massive circuits of linear optical components and effective implementation of entangling operations on photons. By using large-scale silicon photonic circuits to implement an extension of the linear combination of quantum operators scheme, we realize a fully programmable two-qubit quantum processor, enabling universal two-qubit quantum information processing in optics. The quantum processor is fabricated with mature CMOS-compatible processing and comprises more than 200 photonic components. We programmed the device to implement 98 different two-qubit unitary operations (with an average quantum process fidelity of 93.2 ± 4.5%), a two-qubit quantum approximate optimization algorithm, and efficient simulation of Szegedy directed quantum walks. This fosters further use of the linear-combination architecture with silicon photonics for future photonic quantum processors.

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Acknowledgements

The authors thank S. Paesani, J. Silverstone, G. Sinclair, K. Aungskunsiri and C. Sparrow for helpful discussions and A. Murray and M. Loutit for assistance with wire-bonding the device. This work was supported by EPSRC programme grant EP/L024020/1, US Army Research Office (ARO) grant no. W911NF-14-1-0133, US Air Force Office of Scientific Research (AFOSR) and the Centre for Nanoscience and Quantum Information (NSQI). X.Q. acknowledges support from the China Scholarship Council and the National Natural Science Foundation of China (NSFC no. 61632021). X.Z. acknowledges support from the National Key Research and Development Program (2017YFA0305200 and 2016YFA0301700), the National Young 1000 Talents Plan, and the Natural Science Foundation of Guangdong (2016A030312012). J.W. acknowledges support from the National Young 1000 Talents Plan. T.C.R. acknowledges support from the Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology (project no. CE170100012). J.L.O.B. acknowledges a Royal Society Wolfson Merit Award and a Royal Academy of Engineering Chair in Emerging Technologies. M.G.T. acknowledges support from the ERC starter grant ERC-2014-STG 640079 and an EPSRC Early Career Fellowship EP/K033085/1. J.C.F.M acknowledges support from EPSRC Early Career Fellowship EP/M024385/1.

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Affiliations

  1. Quantum Engineering Technology Labs, HH Wills Physics Laboratory and Department of Electrical & Electronic Engineering, University of Bristol, Bristol, UK

    • Xiaogang Qiang
    • , Jianwei Wang
    • , Callum M. Wilkes
    • , Sean O’Gara
    • , Laurent Kling
    • , Graham D. Marshall
    • , Raffaele Santagati
    • , Jeremy L. O’Brien
    • , Mark G. Thompson
    •  & Jonathan C. F. Matthews
  2. Institute for Quantum Information & State Key Laboratory of High Performance Computing, College of Computer, National University of Defense Technology, Changsha, China

    • Xiaogang Qiang
  3. National Innovation Institute of Defense Technology, AMS, Beijing, China

    • Xiaogang Qiang
  4. State Key Laboratory of Optoelectronic Materials and Technologies and School of Physics, Sun Yat-sen University, Guangzhou, China

    • Xiaoqi Zhou
  5. State Key Laboratory for Mesoscopic Physics and Collaborative Innovation Centre of Quantum Matter, School of Physics, Peking University, Beijing, China

    • Jianwei Wang
  6. School of Physics, The University of Western Australia, Crawley, Western Australia, Australia

    • Thomas Loke
    •  & Jingbo B. Wang
  7. Centre for Quantum Computation and Communication Technology, School of Mathematics and Physics, University of Queensland, Brisbane, Queensland, Australia

    • Timothy C. Ralph

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Contributions

X.Z., X.Q., T.C.R., J.L.O.B. and J.C.F.M. conceived and designed the project. X.Z. and X.Q. designed the device. X.Q., J.W., C.M.W., L.K., G.D.M. and R.S. built the experimental set-up and carried out the experiments. X.Q., X.Z., T.L., S.O.G., J.B.W. and J.C.F.M. performed the theoretical analysis. X.Z., J.L.O.B., M.G.T. and J.C.F.M. managed the project. All authors discussed the results and contributed to writing the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Xiaoqi Zhou or Jonathan C. F. Matthews.

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DOI

https://doi.org/10.1038/s41566-018-0236-y