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Causal loops: Logically consistent correlations, time travel, and computation

Ämin Baumeler
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  • Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-1090 Vienna, Austria
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Published Online: 2019-02-06 | DOI: https://doi.org/10.1515/itit-2019-0005


Causal loops are loops in cause-effect relations, where, say for two events A, B, the event A is a cause of B and, vice versa, B is a cause of A. Such loops are traditionally ruled out due to potential logical problems, e. g., where an effect suppresses its own cause. Motivated by our current physical theories, we show that not only causal loops exist that are logically consistent, but that these loops are computationally tame and help to further investigate on the theoretical foundations of time travel. Causal loops do not necessarily pose problems from a logics, computer-science, and physics point of view. This opens their potential applicability in various fields from philosophy of language to computer science and physics.

Keywords: causality; fixed points; closed time-like curves; ∩UPcoUP

ACM CCS: Theory of computationModels of computationAbstract machinesTheory of computationComputational complexity and cryptographyComplexity theory and logicTheory of computationModels of computationQuantum computation theory


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About the article

Ämin Baumeler

Dr. Ämin Baumeler studied computer science at ETH Zurich, Switzerland. His master’s project on quantum cryptography was conducted at the Institute for Quantum Computing in Waterloo, Canada, under the supervision of Prof. Anne Broadbent. After having obtained the master’s degree from ETH, he started his PhD studies in the research group of Prof. Stefan Wolf at the Faculty of Informatics, Università della Svizzera italiana, Lugano, Switzerland. The research performed in his PhD studies are on causal structures, foundations of quantum theory, and complexity theory. After having obtained the PhD degree in 2016, he moved to Vienna to join Prof. Časlav Brukner’s group at the Institute for Quantum Optics and Quantum Information.

Received: 2019-01-22

Accepted: 2019-01-28

Published Online: 2019-02-06

Citation Information: it - Information Technology, ISSN (Online) 2196-7032, ISSN (Print) 1611-2776, DOI: https://doi.org/10.1515/itit-2019-0005.

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