{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"975086e7207fd60a060cca3dd7b43e204b4589cbb6f015b862c8625b8d144f80","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["55268ade1f15b9abc4e50a95c83b1a482242f784d00905b63b21a75143294625","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"9d2fb072cad8d54b7b6674e08b228ba54151cec8e31b06cf40dd2401f54ba492","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":["ai:gpt-5.5"],"external_id":"qi.contextuality-nonlocality.werner-povm-locality","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Measurements can be generalized beyond simple projections by using helper systems. For Werner states it is unknown whether such generalized measurements reveal nonlocality at higher noise than projective ones.","posed_since":"2002","precise":"Let $v_c^{\\mathrm{POVM}}$ be the critical visibility of $\\rho_W(v)$ under arbitrary local POVMs. Known: $\\rho_W(v)$ is local for all POVMs when $v \\le 1/2$ (Zhang and Chitambar, arXiv:2309.09960) and for projective measurements when $v \\le 0.6875$. Determine whether $v_c^{\\mathrm{POVM}}$ equals the projective threshold $v_c$.","problem_ref":"55268ade1f15b9abc4e50a95c83b1a482242f784d00905b63b21a75143294625","references":"","settled_by":"A local model for all POVMs up to the projective threshold, or a POVM Bell inequality violated below it.","status_note":"The analogous steering question was settled in 2023: POVMs give no advantage and the threshold is $v = 1/2$ (arXiv:2309.09960).","title":"Do general measurements beat projective ones for Werner-state nonlocality?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"83b6454d72ff6dcfc89405299cf3a796c12cb8118e689eb2811781314992cd33","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"94f4a36fee40b25e17ba7df3d96d4b74cbcef5f1cc7d636f782fcb80a98ebab3","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"GeBgxNRVx836_ig89mDP3NHpywTwR961iMAJZ6e7xq3X-YaIJKNae2MTa3EMHyiMzDMf9IWaqzoazPNtEt19DA"},"schema":"pubphys.envelope/1"},"record_hash":"83b6454d72ff6dcfc89405299cf3a796c12cb8118e689eb2811781314992cd33","leaf_index":3706}