{
  "id": "cond-mat/9811029",
  "version": "v2",
  "published": "1998-11-03T14:55:23.000Z",
  "updated": "1999-12-02T17:48:43.000Z",
  "title": "Josephson-Junction Qubits and the Readout Process by Single-Electron Transistors",
  "authors": [
    "Yuriy Makhlin",
    "Gerd Schoen",
    "Alexander Shnirman"
  ],
  "comment": "RevTex, 19 pages, 9 figures; contribution to \"Exploring the Quantum-Classical Frontier: Recent Advances in Macroscopic and Mesoscopic Quantum Phenomena.\" Eds. J.R.Friedman and S.Han Presentation improved",
  "journal": "In: Exploring the Quantum-Classical Frontier, pp. 405-440. Eds. J.R. Friedman and S. Han, Nova Science, Commack, NY, 2002",
  "categories": [
    "cond-mat.mes-hall",
    "quant-ph"
  ],
  "abstract": "Several physical realizations of quantum bits have been proposed. Of those, nano-electronic devices appear most suitable for large-scale integration and potential applications. We suggest to use low-capacitance Josephson junctions, exploiting the coherence of tunneling in the superconducting state combined with the possibility to control individual charges by Coulomb blockade effects (cond-mat/9706016,cond-mat/9808067). These systems constitute quantum bits, with logical states differing by one Cooper-pair charge. Single- and two-bit operations can be performed by applying a sequence of gate voltages. The phase coherence time is sufficiently long to allow a series of these steps. In addition to the manipulation of qubits the resulting quantum state has to be read out. This can be accomplished by coupling a single-electron transistor capacitively to the qubit (cond-mat/9801125). To describe this quantum measurement process we study the time evolution of the density matrix of the coupled system. Only when a transport voltage is turned on, the transistor destroys the phase coherence of the qubit; in this case within a short time. The measurement is accomplished after a longer time scale, when the signal resolves the different quantum states. At still longer times the measurement process itself destroys the information about the initial state. We present a suitable set of system parameters, which can be realized by present-day technology.",
  "revisions": [
    {
      "version": "v2",
      "updated": "1999-12-02T17:48:43.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "single-electron transistor",
      "josephson-junction qubits",
      "readout process",
      "quantum state",
      "measurement process"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "RevTeX",
      "pages": 19,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "1998cond.mat.11029M"
    }
  }
}