{
  "id": "quant-ph/0306143",
  "version": "v1",
  "published": "2003-06-20T23:01:41.000Z",
  "updated": "2003-06-20T23:01:41.000Z",
  "title": "A quantum gate array can be programmed to evaluate the expectation value of any operator",
  "authors": [
    "Juan Pablo Paz",
    "Augusto Roncaglia"
  ],
  "comment": "4 pages, 3 figures included",
  "doi": "10.1103/PhysRevA.68.052316",
  "categories": [
    "quant-ph"
  ],
  "abstract": "A programmable gate array is a circuit whose action is controlled by input data. In this letter we describe a special--purpose quantum circuit that can be programmed to evaluate the expectation value of any operator $O$ acting on a space of states of $N$ dimensions. The circuit has a program register whose state $|\\Psi(O)>_P$ encodes the operator $O$ whose expectation value is to be evaluated. The method requires knowledge of the expansion of $O$ in a basis of the space of operators. We discuss some applications of this circuit and its relation to known instances of quantum state tomography.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2003-06-20T23:01:41.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "expectation value",
      "quantum gate array",
      "quantum state tomography",
      "special-purpose quantum circuit",
      "input data"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "publisher": "APS",
      "journal": "Phys. Rev. A"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 4,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}