Quantum operations with indefinite time direction
Abstract
The fundamental dynamics of quantum particles is neutral with respect to the arrow of time. And yet, our experiments are not: we observe quantum systems evolving from the past to the future, but not the other way round. A fundamental question is whether it is possible, at least in principle, to conceive a broader set of operations that probe quantum processes in the backward direction, from the future to the past, or more generally, in a combination of the forward and backward directions. Here we introduce a mathematical framework for operations that are not constrained to a definite time direction. More generally, we introduce a set of multipartite operations that include indefinite time direction as well as indefinite causal order, providing a framework for potential extensions of quantum theory.
- Publication:
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Communications Physics
- Pub Date:
- December 2022
- DOI:
- 10.1038/s42005-022-00967-3
- arXiv:
- arXiv:2012.03859
- Bibcode:
- 2022CmPhy...5..190C
- Keywords:
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- Quantum Physics;
- Mathematical Physics
- E-Print:
- 7 + 21 pages, 4 figures