Coherent manipulation of an Andreev spin qubit

  1. M. Hays,
  2. V. Fatemi,
  3. D. Bouman,
  4. J. Cerrillo,
  5. S. Diamond,
  6. K. Serniak,
  7. T. Connolly,
  8. P. Krogstrup,
  9. J. Nygård,
  10. A. Levy Yeyati,
  11. A. Geresdi,
  12. and M. H. Devoret
Two promising architectures for solid-state quantum information processing are electron spins in semiconductor quantum dots and the collective electromagnetic modes of superconducting circuits. In some aspects, these two platforms are dual to one another: superconducting qubits are more easily coupled but are relatively large among quantum devices (∼mm), while electrostatically-confined electron spins are spatially compact (∼μm) but more complex to link. Here we combine beneficial aspects of both platforms in the Andreev spin qubit: the spin degree of freedom of an electronic quasiparticle trapped in the supercurrent-carrying Andreev levels of a Josephson semiconductor nanowire. We demonstrate coherent spin manipulation by combining single-shot circuit-QED readout and spin-flipping Raman transitions, finding a spin-flip time TS=17 μs and a spin coherence time T2E=52 ns. These results herald a new spin qubit with supercurrent-based circuit-QED integration and further our understanding and control of Andreev levels — the parent states of Majorana zero modes — in semiconductor-superconductor heterostructures.
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