Plenary Talk 1 - Existence of processes violating causal inequalities on time-delocalised subsystems

Authors: Julian Wechs (presenting), Cyril Branciard and Ognyan Oreshkov
Title: Existence of processes violating causal inequalities on time-delocalised subsystems

[estudiosogarboso]

Introduction of the talk: 2:12
Is indefinite causal order physically realizable? 3:22
Outline of the talk: 4:40
Process Matrix Framework: 5:10
Example of a process matrix: 8:30
"Any process matrix that does not allow Bob to signal to Alice corresponds to a standard quantum circuit acts before Bob": 9:52
Causal inequalities: 11:24
List of optics experiments: 13:48 (up to 2021)
Quantum Switch: 15:07
Time-delocalized systems may be considered as an approach to the "simulation" vs "realization" question: 18:40
What is a time-delocalized system?: 19:20
Proof that time-delocalizing the quantum SWITCH one obtains the usual process matrix picture: 22:21
"All unitary extensions of bipartite processes are variations of a quantum SWITCH": 25:45
Processes violating causal inequalities on time-delocalized systems: 26:16
(MAIN RESULT) Tripartite process matrices can also be written in a superposition of causal orders in a temporal way! 27:44
There are process matrices for the tripartite case that can violate causal inequalities: 29:50
Assumptions behind causal inequalities: 33:30 (Causal order, freedom of choice, closed laboratories)
In the paper they formalize the same assumptions for the multipartite case: 35:40
Conclusion: 40:30
Questions: 44:30