Published: 18th September 2021
DOI: 10.4204/EPTCS.343
ISSN: 2075-2180


Proceedings 18th International Conference on
Quantum Physics and Logic
Gdansk, Poland, and online, 7-11 June 2021

Edited by: Chris Heunen and Miriam Backens

Conditional Distributions for Quantum Systems
Arthur J. Parzygnat
Generators and Relations for Real Stabilizer Operators
Justin Makary, Neil J. Ross and Peter Selinger
Negative Translations of Orthomodular Lattices and Their Logic
Wesley Fussner and Gavin St. John
Relating Measurement Patterns to Circuits via Pauli Flow
Will Simmons
Bennett and Stinespring, Together at Last
Chris Heunen and Robin Kaarsgaard
Restricted Hidden Cardinality Constraints in Causal Models
Beata Zjawin, Elie Wolfe and Robert W. Spekkens
Diagrammatic Differentiation for Quantum Machine Learning
Alexis Toumi, Richie Yeung and Giovanni de Felice
Generators and Relations for Un(Z[1/2,i])
Xiaoning Bian and Peter Selinger
CPM Categories for Galois Extensions
James Hefford and Stefano Gogioso
Quantum Algorithms and Oracles with the Scalable ZX-calculus
Titouan Carette, Yohann D'Anello and Simon Perdrix
Generators and Relations for the Group On(Z[1/2])
Sarah Meng Li, Neil J. Ross and Peter Selinger
Causality in Higher Order Process Theories
Matt Wilson and Giulio Chiribella
The Sheaf-Theoretic Structure of Definite Causality
Stefano Gogioso and Nicola Pinzani


This volume contains the proceedings of the 18th International Conference on Quantum Physics and Logic (QPL 2021), June 7-11, 2021 online at the International Centre for Theory of Quantum Technologies (ICTQT) at the University of Gdańsk, Poland and was attended by 768 registered participants.

QPL is a conference that brings together researchers working on mathematical foundations of quantum physics, quantum computing, and related areas, with a focus on structural perspectives and the use of logical tools, ordered algebraic and category-theoretic structures, formal languages, semantical methods, and other computer science techniques applied to the study of physical behaviour in general. Work that applies structures and methods inspired by quantum theory to other fields (including computer science) was also welcome.

Previous QPL events were held in Paris (2020, online), Orange (2019), Halifax (2018), Nijmegen (2017), Glasgow (2016), Oxford (2015), Kyoto (2014), Barcelona (2013), Brussels (2012), Nijmegen (2011), Oxford (2010), Oxford (2009), Reykjavik (2008), Oxford (2006), Chicago (2005), Turku (2004), and Ottawa (2003).

The QPL conference program included four invited lectures:

It also included two invited tutorials:

As well as four invited industry talks:

The conference program also included 37 scheduled and 32 unscheduled contributed talks, as well as 29 posters, chosen from a record 122 total submissions. They were selected by the program committee, which was chaired by Miriam Backens and Chris Heunen. The other members of the program committee were Antonio Acín, Bárbara Amaral, Pablo Arrighi, Jonathan Barrett, Alessandro Bisio, Anne Broadbent, Ulysse Chabaud, Bob Coecke, Alejandro Díaz-Caro, Ross Duncan, Yuan Feng, Alexandru Gheorghiu, Stefano Gogioso, Teiko Heinosaari, Matthew Hoban, Kohei Kishida, Aleks Kissinger, Ravi Kunjwal, Ciarán Lee, Matt Leifer, Martha Lewis, Shane Mansfield, Simon Martiel, Hector Miller-Bakewell, Mio Murao, Gláucia Murta, Ognyan Oreshkov, Prakash Panangaden, Simon Perdrix, Lídia del Rio, Julien Ross, Mehrnoosh Sadrzadeh, Ana Belén Sainz, John H. Selby, Rui Soares Barbosa, Rob Spekkens, Isar Stubbe, Benoît Valiron, Jamie Vicary, John van de Wetering, Alexander Wilce, Mingsheng Ying, Vladimir Zamdzhiev, and Margherita Zorzi.

Each submission was thoroughly refereed, and reviewers delivered detailed and insightful comments and suggestions. The program chairs thank all the program committee members and all the additional reviewers for their excellent service.

There were three submission categories at QPL 2021: original contributions, consisting of a 5-12 page extended abstract, shorter extended abstracts of work published or submitted elsewhere, and poster-only submissions. This volume contains papers corresponding to a selection of the original contributions.

At each QPL conference, an award for the best student paper is given at the discretion of the program committee. Papers eligible for the award are those where all the authors are students (or at an equivalent career stage) at the time of submission. This year's best student paper award went to Will Simmons of Cambridge Quantum Computing for the paper Relating measurement patterns to circuits via Pauli flow and Pauli Dependency DAGs.

The local organizers were John H. Selby, Ana Belén Sainz, Ewa Kaszewska, and Marcin Górzny. The inclusivity and safety team were Dominic Horsman, Shane Mansfield, and Ana Belén Sainz. The website managers were Hector Miller-Bakewell and Marcin Górzny. The steering committee for the QPL conference series consists of Bob Coecke, Prakash Panangaden, and Peter Selinger. The conference enjoyed financial support from: Cambridge Quantum Computing, Google, and the Institute for Quantum Computing (IQC) at the University of Waterloo.

The PC chairs,

Miriam Backens (University of Birmingham) and Chris Heunen (University of Edinburgh).