,
Thomas Ehrhard
,
Claudia Faggian
Creative Commons Attribution 4.0 International license
Quantum Bayesian networks [Henson et al., 2014] provide a mathematical formalism to describe causal relations, to analyse correlations, and to predict the probabilities of measurement outcomes, in systems involving both classical and quantum data. They generalize Pearl’s Bayesian networks [Pearl, 2009] - prominent graphical models for classical probabilistic reasoning and inference. The goal of this paper is to bring compositional principles and a typing discipline into this setting. A key feature of our compositional semantics is that when all causes are classical, it coincides with the standard factor-based semantics of Bayesian networks, while in the purely quantum case it reduces to tensor networks. We then propose a typed formalism based on linear logic proof-nets, where types ensure well-behaved composition of systems, and which we prove sound and complete with respect to quantum Bayesian networks.
@InProceedings{diguardia_et_al:LIPIcs.FSCD.2026.16,
author = {Di Guardia, R\'{e}mi and Ehrhard, Thomas and Faggian, Claudia},
title = {{Quantum Bayesian Networks: Compositionality and Typing via Linear Logic}},
booktitle = {11th International Conference on Formal Structures for Computation and Deduction (FSCD 2026)},
pages = {16:1--16:23},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-433-8},
ISSN = {1868-8969},
year = {2026},
volume = {378},
editor = {Pfenning, Frank},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.FSCD.2026.16},
URN = {urn:nbn:de:0030-drops-263668},
doi = {10.4230/LIPIcs.FSCD.2026.16},
annote = {Keywords: Quantum Bayesian Networks, Quantum Causal Models, Bayesian Networks, Proof-Nets, Linear Logic}
}