{
  "id": "1403.4565",
  "version": "v3",
  "published": "2014-03-18T18:30:37.000Z",
  "updated": "2015-05-19T13:15:22.000Z",
  "title": "Coherent dynamics in long fluxonium qubits",
  "authors": [
    "G. Rastelli",
    "M. Vanevic",
    "W. Belzig"
  ],
  "comment": "20 pages, 8 figures (new, substantially revised version)",
  "journal": "New J. Phys. 17 (2015) 053026",
  "doi": "10.1088/1367-2630/17/5/053026",
  "categories": [
    "cond-mat.mes-hall",
    "cond-mat.supr-con"
  ],
  "abstract": "We analyze the coherent dynamics of a fluxonium device (Manucharyan et al 2009 Science 326 113) formed by a superconducting ring of Josephson junctions in which strong quantum phase fluctuations are localized exclusively on a single weak element. In such a system, quantum phase tunnelling by $2\\pi $ occurring at the weak element couples the states of the ring with supercurrents circulating in opposite directions, while the rest of the ring provides an intrinsic electromagnetic environment of the qubit. Taking into account the capacitive coupling between nearest neighbors and the capacitance to the ground, we show that the homogeneous part of the ring can sustain electrodynamic modes which couple to the two levels of the flux qubit. In particular, when the number of Josephson junctions is increased, several low-energy modes can have frequencies lower than the qubit frequency. This gives rise to a quasiperiodic dynamics, which manifests itself as a decay of oscillations between the two counterpropagating current states at short times, followed by oscillation-like revivals at later times. We analyze how the system approaches such a dynamics as the ring's length is increased and discuss possible experimental implications of this non-adiabatic regime.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2014-03-25T14:31:54.000Z",
      "title": "Quasiperiodicity and revivals in dynamics of quantum phase slips in Josephson junction chains and superconducting nanowires",
      "abstract": "Quantum phase slips in superconducting loops threaded by an external magnetic field provide a coupling between macroscopic quantum states with supercurrents circulating in opposite directions. We analyze the dynamics of the phase slips as a function of the superconducting loop length, from fully coherent dynamics for short loops to dissipative dynamics for the long ones. For intermediate lengths of the superconducting loop, the phase slips are coupled to a discrete bath of oscillators with frequencies comparable to the phase-slip amplitude. This gives rise to a quasiperiodic dynamics of the phase slips which manifests itself as a decay of oscillations between the two counterpropagating current states at short times, followed by oscillation revivals at later times. We analyze possible experimental implications of this non-adiabatic regime in Josephson junction chains and superconducting nanowires.",
      "comment": "10 pages, 8 figures (The figures and the conclusion sections were modified; Appendices A and B were added; minor modifications in other sections)",
      "journal": null,
      "doi": null
    },
    {
      "version": "v3",
      "updated": "2015-05-19T13:15:22.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "quantum phase slips",
      "josephson junction chains",
      "superconducting nanowires",
      "superconducting loop",
      "quasiperiodicity"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "publisher": "IOP",
      "journal": "New Journal of Physics",
      "year": 2015,
      "month": "May",
      "volume": 17,
      "number": 5,
      "pages": "053026"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 20,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2015NJPh...17e3026R"
    }
  }
}