Anharmonicity of a Gatemon Qubit with a Few-Mode Josephson Junction

  1. A. Kringhøj,
  2. L. Casparis,
  3. M. Hell,
  4. T. W. Larsen,
  5. F. Kuemmeth,
  6. M. Leijnse,
  7. K. Flensberg,
  8. P. Krogstrup,
  9. J. Nygård,
  10. K. D. Petersson,
  11. and C. M. Marcus
Coherent operation of gate-voltage-controlled hybrid transmon qubits (gatemons) based on semiconductor nanowires was recently demonstrated. Here we experimentally investigate the anharmonicity in epitaxial InAs-Al Josephson junctions, a key parameter for their use as a qubit. Anharmonicity is found to be reduced by roughly a factor of two compared to conventional metallic junctions, and dependent on gate voltage. Experimental results are consistent with a theoretical model, indicating that Josephson coupling is mediated by a small number of highly transmitting modes in the semiconductor junction.

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