{
  "id": "0804.0087",
  "version": "v1",
  "published": "2008-04-01T07:16:59.000Z",
  "updated": "2008-04-01T07:16:59.000Z",
  "title": "Beating the standard quantum limit: Phase super-sensitivity of N-photon interferometers",
  "authors": [
    "Ryo Okamoto",
    "Holger F. Hofmann",
    "Tomohisa Nagata",
    "Jeremy L. O'Brien",
    "Keiji Sasaki",
    "Shigeki Takeuchi"
  ],
  "comment": "submitted for publication Oct 2007, 5pages, 3figures",
  "doi": "10.1088/1367-2630/10/7/073033",
  "categories": [
    "quant-ph"
  ],
  "abstract": "Quantum metrology promises greater sensitivity for optical phase measurements than could ever be achieved classically. Here we present a theory of the phase sensitivity for the general case where the detection probability is given by an $N$ photon interference fringe. We find that the phase sensitivity has a complex dependence on both the intrinsic efficiency of detection $\\eta$ and the interference fringe visibility $V$. Most importantly, the phase that gives maximum phase sensitivity is in general not the same as the phase at which the slope of the interference fringe is a maximum, as has previously been assumed. We determine the parameter range where quantum enhanced sensitivity can be achieved. In order to illustrate these theoretical results, we perform a four photon experiment with $\\eta=3/4$ and $V=82\\pm6$% (an extension of our previous work [Science \\textbf{316}, 726 (2007)]) and find a phase sensitivity 1.3 times greater than the standard quantum limit at a phase different to that which gives maximum slope of the interference fringe.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2008-04-01T07:16:59.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "standard quantum limit",
      "n-photon interferometers",
      "phase sensitivity",
      "phase super-sensitivity",
      "interference fringe"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "journal": "New Journal of Physics",
      "year": 2008,
      "month": "Jul",
      "volume": 10,
      "number": 7,
      "pages": "073033"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2008NJPh...10g3033O"
    }
  }
}