Abstract
There has been a body of work deriving the complex Hilbert-space structure of quantum theory from axioms/principles/postulates to deepen our understanding of quantum theory and to reveal ways to go beyond it to resolve foundational issues. Recent progress in incorporating indefinite causal structure into physical theories suggests that a more comprehensive understanding of both quantum theory and the theory beyond it accounts for indefinite causal structure. We formulate a framework of physical theories without assuming definite causal structure and identify postulates that single out the complex Hilbert-space structure. More than one complex Hilbert-space theory is compatible with the postulates, which leaves room for further search for the best among these theories.
- Received 30 June 2018
DOI:https://doi.org/10.1103/PhysRevA.98.032112
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