{
  "id": "0811.4679",
  "version": "v1",
  "published": "2008-11-28T10:11:55.000Z",
  "updated": "2008-11-28T10:11:55.000Z",
  "title": "Entanglement entropy and the determination of an unknown quantum state",
  "authors": [
    "Gerardo Aquino",
    "Filippo Giraldi"
  ],
  "comment": "5 pages 2 figures, accepted for publication on Physical Review A",
  "journal": "Physical Review A, 78, 062115 (2008)",
  "doi": "10.1103/PhysRevA.78.062115",
  "categories": [
    "quant-ph"
  ],
  "abstract": "An initial unknown quantum state can be determined with a single measurement apparatus by letting it interact with an auxiliary, \"Ancilla\", system as proposed by Allahverdyan, Balian and Nieuwenhuizen [Phys. Rev. Lett. 92, 120402 (2004)]. In the case of two qubits, this procedure allows to reconstruct the initial state of the qubit of interest S by measuring three commuting observables and therefore by means of a single apparatus, for the total system S + A at a later time. The determinant of the matrix of the linear transformation connecting the measurements of three commuting observables at time t > 0 to the components of the polarization vector of S at time t = 0 is used as an indicator of the reconstructability of the initial state of the system S. We show that a connection between the entanglement entropy of the total system S + A and such a determinant exists, and that for a pure state a vanishing entanglement individuates, without a need for any measurement, those intervals of time for which the reconstruction procedure is least efficient. This property remains valid for a generic dimension of S. In the case of a mixed state this connection is lost.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2008-11-28T10:11:55.000Z"
    }
  ],
  "analyses": {
    "subjects": [
      "03.65.Wj",
      "03.65.Ud",
      "05.30.-d",
      "05.70.Ln"
    ],
    "keywords": [
      "entanglement entropy",
      "total system",
      "initial unknown quantum state",
      "determination",
      "initial state"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "publisher": "APS",
      "journal": "Physical Review A",
      "year": 2008,
      "month": "Dec",
      "volume": 78,
      "number": 6,
      "pages": "062115"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2008PhRvA..78f2115A"
    }
  }
}