Quantum space-time marginal problem: global causal structure from local causal information

Autor: Zhian Jia, Minjeong Song, Dagomir Kaszlikowski
Jazyk: angličtina
Rok vydání: 2023
Předmět:
Zdroj: New Journal of Physics, Vol 25, Iss 12, p 123038 (2023)
Druh dokumentu: article
ISSN: 1367-2630
DOI: 10.1088/1367-2630/ad1416
Popis: Spatial and temporal quantum correlations can be unified in the framework of the pseudo-density operators (PDOs), and quantum causality between the involved events in an experiment is encoded in the corresponding PDO. We study the relationship between local causal information and global causal structure. A space-time marginal problem is proposed to infer global causal structures from given marginal causal structures where causal structures are represented by the reduced PDOs; we show that there almost always exists a solution in this case. By imposing the corresponding constraints on this solution set, we could obtain the required solutions for special classes of marginal problems, like a positive semidefinite marginal problem, separable marginal problem, etc. We introduce a space-time entropy and propose a method to determine the global causal structure based on the maximum entropy principle. The notion of quantum pseudo-channel (QPC) is also introduced and we demonstrate that the QPC marginal problem can be solved by transforming it into a PDO marginal problem via the channel-state duality.
Databáze: Directory of Open Access Journals