On the noncausality – local indistinguishability equivalence and beyondConfirmed

by Hippolyte Dourdent (ICFO, Barcelona)

Monday Mar 16, 2026, 11:00 AM → 12:30 PM America/Toronto

PI/3-301 - Alice Room (Perimeter Institute for Theoretical Physics)

Local indistinguishability - often called "quantum nonlocality without entanglement" (QNLWE) - describes the counterintuitive situation where orthogonal product states cannot be discriminated by local operations and classical communication (LOCC). Kunjwal and Baumeler [PRL 131, 120201 (2023)] showed that this limitation can be traded against definite causal order while preserving classical communication, establishing an equivalence between the tripartite noncausal "Lugano" process and the QNLWE "SHIFT" basis, and showing that all Boolean process functions -- logically consistent multipartite classical communications that may violate causal inequalities -- without a global past map onto a QNLWE basis.