{
  "id": "cond-mat/0507290",
  "version": "v1",
  "published": "2005-07-13T07:57:08.000Z",
  "updated": "2005-07-13T07:57:08.000Z",
  "title": "Dephasing of a flux-qubit coupled to a harmonic oscillator",
  "authors": [
    "P. Bertet",
    "I. Chiorescu",
    "C. J. P. M Harmans",
    "J. E. Mooij"
  ],
  "categories": [
    "cond-mat.mes-hall",
    "cond-mat.supr-con"
  ],
  "abstract": "Decoherence in superconducting qubits is known to arise because of a variety of environmental degrees of freedom. In this article, we focus on the influence of thermal fluctuations in a weakly damped circuit resonance coupled to the qubit. Because of the coupling, the qubit frequency is shifted by an amount $n \\delta \\nu_0$ if the resonator contains $n$ energy quanta. Thermal fluctuations induce temporal variations $n(t)$ and thus dephasing. We give an approximate formula for the qubit dephasing time as a function of $\\delta \\nu_0$. We discuss the specific case of a flux-qubit coupled to the plasma mode of its DC-SQUID detector. We first derive a plasma mode-qubit interaction hamiltonian which, in addition to the usual Jaynes-Cummings term, has a coupling term quadratic in the oscillator variables coming from the flux-dependence of the SQUID Josephson inductance. Our model predicts that $\\delta \\nu_0$ cancels in certain non-trivial bias conditions for which dephasing due to thermal fluctuations should be suppressed.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2005-07-13T07:57:08.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "harmonic oscillator",
      "flux-qubit",
      "thermal fluctuations induce temporal variations",
      "damped circuit resonance",
      "plasma mode-qubit interaction hamiltonian"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2005cond.mat..7290B"
    }
  }
}