{
  "id": "1306.1795",
  "version": "v3",
  "published": "2013-06-07T17:54:16.000Z",
  "updated": "2013-10-19T15:06:22.000Z",
  "title": "Quantum state cloning using Deutschian closed timelike curves",
  "authors": [
    "Todd A. Brun",
    "Mark M. Wilde",
    "Andreas Winter"
  ],
  "comment": "6 pages, 1 figure; v2: modifications to the interpretation of our results based on the insightful comments of the referees; v3: minor change, accepted for publication in Physical Review Letters",
  "journal": "Physical Review Letters vol. 111, no. 19, page 190401, November 2013",
  "doi": "10.1103/PhysRevLett.111.190401",
  "categories": [
    "quant-ph"
  ],
  "abstract": "We show that it is possible to clone quantum states to arbitrary accuracy in the presence of a Deutschian closed timelike curve (D-CTC), with a fidelity converging to one in the limit as the dimension of the CTC system becomes large---thus resolving an open conjecture from [Brun et al., Physical Review Letters 102, 210402 (2009)]. This result follows from a D-CTC-assisted scheme for producing perfect clones of a quantum state prepared in a known eigenbasis, and the fact that one can reconstruct an approximation of a quantum state from empirical estimates of the probabilities of an informationally-complete measurement. Our results imply more generally that every continuous, but otherwise arbitrarily non-linear map from states to states can be implemented to arbitrary accuracy with D-CTCs. Furthermore, our results show that Deutsch's model for CTCs is in fact a classical model, in the sense that two arbitrary, distinct density operators are perfectly distinguishable (in the limit of a large CTC system); hence, in this model quantum mechanics becomes a classical theory in which each density operator is a distinct point in a classical phase space.",
  "revisions": [
    {
      "version": "v3",
      "updated": "2013-10-19T15:06:22.000Z"
    }
  ],
  "analyses": {
    "subjects": [
      "03.65.Wj",
      "03.67.Dd",
      "03.67.Hk",
      "04.20.Gz"
    ],
    "keywords": [
      "deutschian closed timelike curve",
      "quantum state cloning",
      "arbitrary accuracy",
      "clone quantum states",
      "distinct density operators"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "publisher": "APS",
      "journal": "Physical Review Letters",
      "year": 2013,
      "month": "Nov",
      "volume": 111,
      "number": 19,
      "pages": 190401
    },
    "note": {
      "typesetting": "TeX",
      "pages": 6,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2013PhRvL.111s0401B"
    }
  }
}