A modular quantum computer based on a quantum state router

  1. Chao Zhou,
  2. Pinlei Lu,
  3. Matthieu Praquin,
  4. Tzu-Chiao Chien,
  5. Ryan Kaufman,
  6. Xi Cao,
  7. Mingkang Xia,
  8. Roger Mong,
  9. Wolfgang Pfaff,
  10. David Pekker,
  11. and Michael Hatridge
In this work, we present the design of a superconducting, microwave quantum state router which can realize all-to-all couplings among four quantum modules. Each module consists of a single transmon, readout mode, and communication mode coupled to the router. The router design centers on a parametrically driven, Josephson-junction based three-wave mixing element which generates photon exchange among the modules‘ communication modes. We first demonstrate SWAP operations among the four communication modes, with an average full-SWAP time of 760 ns and average inter-module gate fidelity of 0.97, limited by our modes‘ coherences. We also demonstrate photon transfer and pairwise entanglement between the modules‘ qubits, and parallel operation of simultaneous SWAP gates across the router. These results can readily be extended to faster and higher fidelity router operations, as well as scaled to support larger networks of quantum modules.
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