{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"2f54e97866c265fdd761248d9616a1061431bbd3493dee904cb23d8fcd143d4c","created":"2026-10-03T07:18:10Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"de8c3b20ed28b5cbb0d0284e82973568eb81b8226cf44fc0700f8ded2473490f","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"qi.quantum-principles.higher-order-gpt","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Quantum theory forbids interference that needs three paths at once. The question is whether any other self-consistent probabilistic theory allows it, which fixes what a positive three-slit test would mean.","posed_since":"","precise":"Within generalized probabilistic theories (GPTs), determine whether a theory with nonzero third-order interference $I_3$ exists that satisfies causality, tomographic locality and a consistent composition rule with entangled states. Barnum, Lee, Scandolo and Selby (Entropy 2017, arXiv:1704.05106) showed that causality, purity preservation, pure sharpness and purification together exclude higher-order interference; the task is to find which postulates can be dropped.","problem_ref":null,"references":"","settled_by":"An explicit GPT with $I_{3} != 0$ obeying the stated postulates, or an exclusion theorem from weaker postulates.","status_note":"Excluded under purity principles in 2017 (arXiv:1704.05106); which postulate must fail to allow higher-order interference is open.","title":"Can a consistent theory beyond quantum mechanics have three-path interference?","topic_ref":"26891b8e1768832b53e0431c42eec2be3991112a72dbe42379ae527cbe11ff25"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"a487bb1746dae998da9afa28c5cb79124eca766625f3ad3ebc38bdedb5ded151","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"35fbc1e644b2a9090cbd5cdcbb670a79825e00c2b9ab556f308ea1f3ac8f1b64","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"Hyd0bluQGV7YlOs2Mg4ub60ka9TvLDWlS6cC5wHr_6Yd9Y-A-i9n_BV6sZjc1mNseXFsiCbmTy0YiH_k1Wn0BA"},"schema":"pubphys.envelope/1"},"record_hash":"a487bb1746dae998da9afa28c5cb79124eca766625f3ad3ebc38bdedb5ded151","leaf_index":2030}