{
  "id": "0807.4108",
  "version": "v2",
  "published": "2008-07-25T14:35:08.000Z",
  "updated": "2008-11-21T10:46:57.000Z",
  "title": "Phase variance of squeezed vacuum states",
  "authors": [
    "Emilio Bagan",
    "Alex Monras",
    "Ramon Munoz-Tapia"
  ],
  "comment": "Minor changes, version to appear in PRA, 8 pages, 2 figures",
  "journal": "Phys. Rev. A 78, 043829 (2008)",
  "doi": "10.1103/PhysRevA.78.043829",
  "categories": [
    "quant-ph"
  ],
  "abstract": "We consider the problem of estimating the phase of squeezed vacuum states within a Bayesian framework. We derive bounds on the average Holevo variance for an arbitrary number $N$ of uncorrelated copies. We find that it scales with the mean photon number, $n$, as dictated by the Heisenberg limit, i.e., as $n^{-2}$, only for $N>4$. For $N\\leq 4$ this fundamental scaling breaks down and it becomes $n^{-N/2}$. Thus, a single squeezed vacuum state performs worse than a single coherent state with the same energy. We find the optimal splitting of a fixed given energy among various copies. We also compute the variance for repeated individual measurements (without classical communication or adaptivity) and find that the standard Heisenberg-limited scaling $n^{-2}$ is recovered for large samples.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2008-11-21T10:46:57.000Z"
    }
  ],
  "analyses": {
    "subjects": [
      "42.50.Dv",
      "03.67.Hk",
      "03.65.Wj"
    ],
    "keywords": [
      "phase variance",
      "squeezed vacuum state performs worse",
      "single squeezed vacuum state performs",
      "single coherent state",
      "mean photon number"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "publisher": "APS",
      "journal": "Physical Review A",
      "year": 2008,
      "month": "Oct",
      "volume": 78,
      "number": 4,
      "pages": "043829"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 8,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2008PhRvA..78d3829B"
    }
  }
}