dorsal/arxiv
View SchemaPower of unentangled measurements on two antiparallel spins
| Authors | T. Vértesi |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0611201 |
| URL | https://arxiv.org/abs/quant-ph/0611201 |
| DOI | 10.1103/PhysRevA.75.032343 |
| Journal | Phys. Rev. A 75, 032343 (2007) |
Abstract
We consider a pair of antiparallel spins polarized in a random direction to encode quantum information. We wish to extract as much information as possible on the polarization direction attainable by an unentangled measurement, i.e., by a measurement, whose outcomes are associated with product states. We develop analytically the upper bound 0.7935 bits to the Shannon mutual information obtainable by an unentangled measurement, which is definitely less than the value 0.8664 bits attained by an entangled measurement. This proves our main result, that not every ensemble of product states can be optimally distinguished by an unentangled measurement, if the measure of distinguishability is defined in the sense of Shannon. We also present results from numerical calculations and discuss briefly the case of parallel spins.
{
"annotation_id": "b3fbe0e4-7e3b-4eee-a809-a64d2cc5ef33",
"date_created": "2026-03-02T18:02:34.482000Z",
"date_modified": "2026-03-02T18:02:34.482000Z",
"file_hash": "65807bdc9368d619eeff2fc1522ccdaf8180b149fb0a1d6cc40c8f2cc0899fd7",
"private": false,
"record": {
"abstract": "We consider a pair of antiparallel spins polarized in a random direction to\nencode quantum information. We wish to extract as much information as possible\non the polarization direction attainable by an unentangled measurement, i.e.,\nby a measurement, whose outcomes are associated with product states. We develop\nanalytically the upper bound 0.7935 bits to the Shannon mutual information\nobtainable by an unentangled measurement, which is definitely less than the\nvalue 0.8664 bits attained by an entangled measurement. This proves our main\nresult, that not every ensemble of product states can be optimally\ndistinguished by an unentangled measurement, if the measure of\ndistinguishability is defined in the sense of Shannon. We also present results\nfrom numerical calculations and discuss briefly the case of parallel spins.",
"arxiv_id": "quant-ph/0611201",
"authors": [
"T. V\u00e9rtesi"
],
"categories": [
"quant-ph"
],
"doi": "10.1103/PhysRevA.75.032343",
"journal_ref": "Phys. Rev. A 75, 032343 (2007)",
"title": "Power of unentangled measurements on two antiparallel spins",
"url": "https://arxiv.org/abs/quant-ph/0611201"
},
"schema_id": "dorsal/arxiv",
"source": {
"execution_id": "afcdced5-9848-405a-bb0c-27d8b492291a",
"id": "arXiv Dataset IDs",
"type": "Model",
"variant": "snapshot-2026-03-01",
"version": "0.1.0"
},
"user_id": 1000002
}