{
  "annotation_id": "b81106b9-deaf-4e56-8b71-fed301abfdea",
  "date_created": "2026-03-02T18:02:05.808000Z",
  "date_modified": "2026-03-02T18:02:05.808000Z",
  "file_hash": "bf336bcb69f63ee62b0464a34c644c304a85bbe655039c4d2bd09cd42a8c74a4",
  "private": false,
  "record": {
    "abstract": "We consider N quantum systems initially prepared in pure states and address\nthe problem of unambiguously comparing them. One may ask whether or not all $N$\nsystems are in the same state. Alternatively, one may ask whether or not the\nstates of all N systems are different. We investigate the possibility of\nunambiguously obtaining this kind of information. It is found that some\nunambiguous comparison tasks are possible only when certain linear independence\nconditions are satisfied. We also obtain measurement strategies for certain\ncomparison tasks which are optimal under a broad range of circumstances, in\nparticular when the states are completely unknown. Such strategies, which we\ncall universal comparison strategies, are found to have intriguing connections\nwith the problem of quantifying the distinguishability of a set of quantum\nstates and also with unresolved conjectures in linear algebra. We finally\ninvestigate a potential generalisation of unambiguous state comparison, which\nwe term unambiguous overlap filtering.",
    "arxiv_id": "quant-ph/0402125",
    "authors": [
      "Anthony Chefles",
      "Erika Andersson",
      "Igor Jex"
    ],
    "categories": [
      "quant-ph"
    ],
    "doi": "10.1088/0305-4470/37/29/009",
    "journal_ref": "Journal of Physics A: Mathematical and General, Vol. 37, 7315,\n  2004",
    "title": "Unambiguous comparison of the states of multiple quantum systems",
    "url": "https://arxiv.org/abs/quant-ph/0402125"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "fee916d5-d3af-4d36-aad4-6d2d2c82df87",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}