{
  "id": "1508.06299",
  "version": "v1",
  "published": "2015-08-25T20:35:00.000Z",
  "updated": "2015-08-25T20:35:00.000Z",
  "title": "The Flux Qubit Revisited",
  "authors": [
    "F. Yan",
    "S. Gustavsson",
    "A. Kamal",
    "J. Birenbaum",
    "A. P. Sears",
    "D. Hover",
    "T. J. Gudmundsen",
    "J. L. Yoder",
    "T. P. Orlando",
    "J. Clarke",
    "A. J. Kerman",
    "W. D. Oliver"
  ],
  "categories": [
    "quant-ph"
  ],
  "abstract": "The scalable application of quantum information science will stand on reproducible and controllable high-coherence quantum bits (qubits). In this work, we revisit the design and fabrication of the superconducting flux qubit, achieving a planar device with broad frequency tunability, strong anharmonicity, high reproducibility, and coherence times in excess of 40 us at its flux-insensitive point. Qubit relaxation times across 21 qubits of widely varying designs are consistently matched with a single model involving ohmic charge noise, quasiparticle fluctuations, resonator loss, and 1/f flux noise, a noise source previously considered primarily in the context of dephasing. We furthermore demonstrate that qubit dephasing at the flux-insensitive point is dominated by residual thermal photons in the readout resonator. The resulting photon shot noise is mitigated using a dynamical decoupling protocol, reaching T2 ~ 80 us , approximately the 2T1 limit. In addition to realizing a dramatically improved flux qubit, our results uniquely identify photon shot noise as limiting T2 in contemporary state-of-art qubits based on transverse qubit-resonator interaction.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-08-25T20:35:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "flux qubit",
      "broad frequency tunability",
      "controllable high-coherence quantum bits",
      "results uniquely identify photon shot",
      "contemporary state-of-art qubits"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2015arXiv150806299Y"
    }
  }
}