Appearance of causality in process matrices when performing fixed-basis measurements for two parties
- Author(s)
- Veronika Baumann, Caslav Brukner
- Abstract
The recently developed framework for quantum theory with no global causal order allows for quantum processes in which operations in local laboratories are neither causally ordered nor in a probabilistic mixture of definite causal orders. The causal relation between the laboratories is described by the process matrix. We show that, if the inputs of the laboratories are measured in a fixed basis, one can introduce an effective process matrix which is operationally indistinguishable from the original one. This effective process matrix can be obtained by applying the von Neumann-Lüders update rule for nonselective measurements to the original process matrix and, in the bipartite case, it is compatible with a definite causal order. The latter extends the original Oreshkov et al. proof where one considers that both the measurement of the input and the re-preparation of the output are performed in a fixed basis.
- Organisation(s)
- Quantum Optics, Quantum Nanophysics and Quantum Information
- External organisation(s)
- Università della Svizzera Italiana, Österreichische Akademie der Wissenschaften (ÖAW)
- Journal
- Physical Review A
- Volume
- 93
- No. of pages
- 3
- ISSN
- 1050-2947
- DOI
- https://doi.org/10.1103/PhysRevA.93.062324
- Publication date
- 06-2016
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103025 Quantum mechanics
- ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/281fd72e-fc1b-4ac1-86c3-a071387d8ee1