Preface

This volume contains the proceedings of the 12th International Workshop on Quantum Physics and Logic (QPL 2015), which was held July 15--17, 2015 at Oxford University.

The goal of the QPL workshop series is to bring together researchers working on mathematical foundations of quantum physics, quantum computing, spatio-temporal causal structures, and related areas such as computational linguistics. Of particular interest are topics that use logical tools, ordered algebraic and category-theoretic structures, formal languages, semantical methods and other computer science methods for the study of physical behaviour in general. Earlier workshops in this series, with the same acronym under the name ``Quantum Programming Languages'', were held in Ottawa (2003), Turku (2004), Chicago (2005), and Oxford (2006). The first QPL under the new name Quantum Physics and Logic was held in Reykjavik (2008), followed by Oxford (2009 and 2010), Nijmegen (2011), Brussels (2012), Barcelona (2013), and Kyoto (2014).

The workshop program includes four invited lectures:

• Dan Browne (University College London): "Contextual qubit models from Wigner functions".
• Paul Busch (University of York): "Quantum measurement uncertainty: reading Heisenberg's mind or invoking his spirit?".
• Chris Douglas (University of Oxford): "Topological defects and anyon teleportation"
• Lucien Hardy (Perimeter Institute): "Probabilistic general relativity with agency in an operational framework".

The workshop will be preceded by two days of tutorials:

• Dan Browne (University College London): "Teleportation and Measurement-based computation".
• Paul Busch (University of York): "Quantum uncertainty".
• Oscar Dahlsten (University of Oxford): "Entropy and majorisation in generalised probabilistic theories".
• Pawel Sobocinski (University of Southampton): "Graphical linear algebra".

In addition, there were 37 contributed talks and 16 posters. They were selected by a program committee whose members were John Baez, Dan Browne, Giulio Chiribella, Bob Coecke, Ross Duncan, Tobias Fritz, Simon Gay, Ichiro Hasuo, Chris Heunen (co-chair), Matty Hoban, Bart Jacobs, Viv Kendon, Matt Leifer, Prakash Panangaden, Dusko Pavlovic, Simon Perdrix, Mehrnoosh Sadrzadeh, Peter Selinger (co-chair), Rob Spekkens, Bas Spitters, Isar Stubbe, Jamie Vicary (co-chair), and Mingsheng Ying.

Each submission was refereed by at least three reviewers, who 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. This volume contains papers corresponding to a selection of the contributed talks. In addition, this volume also contains a paper by Furber and Jacobs, corresponding to a talk given at QPL 2013, which had been omitted from the QPL 2013 proceedings due to an editorial oversight.

The local organizers were Destiny Chen, Chris Heunen, and Jamie Vicary.

The steering committee for the QPL workshop series consists of Bob Coecke, Prakash Panangaden, and Peter Selinger.

The workshop enjoyed partial support from the TRUCE project, supported by the European Commision, and the Centre for Quantum Mathematics and Computation at the University of Oxford, supported by the Engineering and Physical Sciences Research Council, and by the Department of Computer Science of the University of Oxford.

September 2015,
Chris Heunen, Peter Selinger, and Jamie Vicary.