{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"5811f5bfb763f8e529fee2519a7df3c6c2bdcc5c971cc42bf7a5376d5cf48a5c","created":"2026-10-03T07:18:09Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"fc3d1b42697ab11f272fe3b8a3eef9c77f6a2de35ebc0cc89fd82077485f99d0","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"qi.causal-order-qrf.switch-genuine-ico","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"A quantum switch sends a photon through devices A and B in a superposition of the orders A-then-B and B-then-A. Critics say each device actually acts at two different times, so the order is definite in spacetime and only appears indefinite.","posed_since":"","precise":"For photonic quantum-switch experiments (operations applied at two distinct times on a time-delocalized subsystem), determine whether the process is causally nonseparable relative to spacetime-localized events, or is a causally ordered circuit on time-delocalized subsystems (Oreshkov, Quantum 2019). An answer is an agreed operational definition of an event and a classification of existing experiments under it.","problem_ref":null,"references":"","settled_by":"A theorem or consensus definition linking process-matrix nonseparability to localized events, applied to the optical experiments.","status_note":"Vilasini and Renner (Phys. Rev. A 110, 022227, 2024) proved that any fixed-spacetime realization uses systems not localized in spacetime and has a fine-grained definite-order description; whether the coarse-grained indefinite order counts as genuine remains disputed.","title":"Do laboratory quantum switches realize genuinely indefinite causal order?","topic_ref":"0d56bf5e6184723e4f024030c3c79a9dde6f6fca1514c152e520bdf56cfb78be"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"e1e2a0be7fc96f372262baf86c3ddb3d675fbc8993dabeb2a24fa31f99038ee0","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"1be0e92bb78f75c89c90b93b26008da1dd9a53c4fcea9359547b3a9f813e454e","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"iP73X-_DLZgJ1UixsDE_8aopjlKgW6yEhm7GlGWhpoqIbki7wbeRcfwcYFcQYLdOOXLOI9361cvQhGYkABB1Aw"},"schema":"pubphys.envelope/1"},"record_hash":"e1e2a0be7fc96f372262baf86c3ddb3d675fbc8993dabeb2a24fa31f99038ee0","leaf_index":1969}