Quantum foundations concerns the conceptual and mathematical underpinnings of quantum theory. In particular, we search for novel quantum effects, consider how to interpret the formalism, ask where the formalism comes from, and how we might modify it. Research at Perimeter Institute is particularly concerned with reconstructing quantum theory from more natural postulates and reformulating the theory in ways that elucidate its conceptual structure. Research in the foundations of quantum theory naturally interfaces with research in quantum information and quantum gravity.
Format results

63 talksCollection NumberC24018
Talk


Tutorial: Causal Inference Meets Quantum Physics
Perimeter Institute for Theoretical Physics 
Counterfactual and Graphical Frameworks for Causal Modeling
University of Washington 

Modeling Latent Selection with Structural Causal Models
University of Amsterdam, Kortewegde Vries Institute for Mathematics 
Relating Wigner's Friend Scenarios to Nonclassical Causal Compatibility, Monogamy Relations, and Fine Tuning
Perimeter Institute for Theoretical Physics 
Zero Inflation as a Missing Data Problem: a Proxybased Approach
Johns Hopkins Whiting School of Engineering 


Quantum Theory (Core), PHYS 605, September 3 – October 4, 2024
14 talksCollection NumberC24036Talk

Lecture  Quantum Theory, PHYS 605
Perimeter Institute for Theoretical Physics 
Lecture  Quantum Theory, PHYS 605
Perimeter Institute for Theoretical Physics 
Lecture  Quantum Theory, PHYS 605
Perimeter Institute for Theoretical Physics 
Lecture  Quantum Theory, PHYS 605
Perimeter Institute for Theoretical Physics 
Lecture  Quantum Theory, PHYS 605
Perimeter Institute for Theoretical Physics 
Lecture  Quantum Theory, PHYS 605
Perimeter Institute for Theoretical Physics 
Lecture  Quantum Theory, PHYS 605
Perimeter Institute for Theoretical Physics 
Lecture  Quantum Theory, PHYS 605
Perimeter Institute for Theoretical Physics


GPTs and the probabilistic foundations of quantum theory  minicourse
7 talksCollection NumberC24021Talk

GPTs and the probabilistic foundations of quantum theory  Lecture
Susquehanna University 
GPTs and the probabilistic foundations of quantum theory  Lecture
Susquehanna University 
GPTs and the probabilistic foundations of quantum theory  Lecture
Susquehanna University 
GPTs and the probabilistic foundations of quantum theory  Lecture
Susquehanna University 
GPTs and the probabilistic foundations of quantum theory  Lecture
Susquehanna University 
GPTs and the probabilistic foundations of quantum theory  Lecture
Susquehanna University 
GPTs and the probabilistic foundations of quantum theory  Lecture
Susquehanna University


Quantum Foundations
13 talksCollection NumberC24008Talk

Quantum Foundations Lecture
Perimeter Institute for Theoretical Physics 
Quantum Foundations Lecture
Perimeter Institute for Theoretical Physics 
Quantum Foundations Lecture
Perimeter Institute for Theoretical Physics 
Quantum Foundations Lecture
Perimeter Institute for Theoretical Physics 
Quantum Foundations Lecture
Perimeter Institute for Theoretical Physics 
Quantum Foundations Lecture
Perimeter Institute for Theoretical Physics 
Quantum Foundations Lecture
Perimeter Institute for Theoretical Physics 
Quantum Foundations Lecture
Perimeter Institute for Theoretical Physics


Causal Inference & Quantum Foundations Workshop
26 talksCollection NumberC23017Talk

Welcome and Opening Remarks
Perimeter Institute for Theoretical Physics 
Tutorial 1
Perimeter Institute for Theoretical Physics 
Graphical models: fundamentals, origins, and beyond
University of Copenhagen 
Towards standard imsets for maximal ancestral graphs
University of Oxford 

Correlations from joint measurements in boxworld and applications to information processing
Institute for Quantum Optics and Quantum Information (IQOQI)  ViennaPIRSA:23040107 
Observational Equivalences Between Causal Structures with Latent Variables
Perimeter Institute for Theoretical Physics 


Quantizing Time
36 talksCollection NumberC21004Talk

Welcome and Opening Remarks

Saint Anselm College

ETH Zurich



KappaMinkowski: physics with noncommutative time
University of Naples Federico II 
Quantizing causation
Perimeter Institute for Theoretical Physics 
Noncausal PageWootters circuits
Institute for Quantum Optics and Quantum Information (IQOQI)  Vienna 
Quantum reference frames for space and spacetime
Institute for Quantum Optics and Quantum Information (IQOQI)  Vienna 

A New Perspective on Time Reversal Motivated by Quantum Gravity
Pennsylvania State University


Quantum Gravity 2020
22 talksCollection NumberC20031Talk

Welcome and Opening Remarks
Perimeter Institute for Theoretical Physics 
Approaches to Quantum Gravity: Key Achievements and Open Issues
MaxPlanckInstitut für Gravitationsphysik 
Quantum gravity from the loop perspective
AixMarseille University 
Lessons for quantum gravity from quantum information theory
Massachusetts Institute of Technology (MIT) 
Understanding of QG from string theory
Princeton University 
Progress in horizon thermodynamics
University of Cambridge 
Asymptotically Safe Amplitudes from the Quantum Effective Action
Radboud Universiteit Nijmegen 
The Remarkable Roundness of the Quantum Universe
Radboud Universiteit Nijmegen


Indefinite Causal Structure
26 talksCollection NumberC19049Talk


10 years of the quantum SWITCH: state of the art and new perspectives
University of Hong Kong (HKU) 
Cyclic quantum causal models and violations of causal inequalities
Université Libre de Bruxelles 
TBA
University of Waterloo 
Composing causal orderings
University of Oxford 
Quantum principle of relativity
University of Warsaw 

What happens when we quantize time?
Saint Anselm College


PSI 2019/2020  Quantum Theory (Branczyk/Dupuis)
14 talksCollection NumberC19038Talk








PSI 2019/2020  Quantum Theory (Dupuis)  Lecture 8
Perimeter Institute for Theoretical Physics


Foundations of Quantum Mechanics
17 talksCollection NumberC18020Talk

Welcome and Opening Remarks
Perimeter Institute for Theoretical Physics 


Local quantum operations and causality
Universidad Nacional Autónoma De Mexico (UNAM) 
Towards synthetic Euclidean quantum field theory
Universität Innsbruck 
Almost quantum correlations violate the norestriction hypothesis
Gdańsk University of Technology 
A deviceindependent approach to testing physical theories from finite data
National Cheng Kung University 
Quantum axiomatics à la carte
Susquehanna University


Algorithmic Information, Induction and Observers in Physics
17 talksCollection NumberC18007Talk


Quantum speedup in testing causal hypotheses
University of Hong Kong (HKU) 
The Logic of Physical Law
Università della Svizzera italiana 
When Causality Is Relaxed: Classical Correlations, Computation, and Time Travel
University of Vienna 
On the concepts of universality in physics and computer science
Universität Innsbruck 
A nogo theorem for observerindependent facts
Institute for Quantum Optics and Quantum Information (IQOQI)  Vienna 

Algorithmic information theory: a critical perspective
LudwigMaximiliansUniversitiät München (LMU)


Observers in Quantum and Foil Theories
11 talksCollection NumberC18006Talk


Compatibility of implicit and explicit observers in quantum theory and beyond
Institute for Quantum Optics and Quantum Information (IQOQI)  ViennaPIRSA:18040084 
From observers to physics via algorithmic information theory I
Institute for Quantum Optics and Quantum Information (IQOQI)  ViennaPIRSA:18040078 
From observers to physics via algorithmic information theory II
Institute for Quantum Optics and Quantum Information (IQOQI)  ViennaPIRSA:18040080 
Motility of the internalexternal cut as a foundational principle
Perimeter Institute for Theoretical PhysicsPIRSA:18040073 




Causalworlds
63 talksCollection NumberC24018Understanding causality is fundamental to science and inspires wideranging applications, yet there are several distinct notions of causation. Recently, there have been important developments on the role of causality in quantum physics, relativistic physics and their interplay. These have unearthed a plethora of fascinating open questions regarding the nature of causation, emergence of spacetime structure and the limits of quantum information processing. At the same time, causal reasoning has become an important tool in machine learning and statistics, with applications ranging from big data to healthcare. This conference brings together experts from different areas of physics working on questions related to causality, as well as selected researchers who bridge the gap between fundamental research and current industrial applications. The aim of the conference is to provide a venue for crosspollination of these ideas through scientific exchange between these communities. The conference will focus on the following facets of causality:
• Quantum and classical causal inference
• Indefinite causal order and quantum reference frames
• Causality in quantum field theory and quantum gravity
• Experiments and applications of causality
:: :: ::
Important dates
Paper submission deadline: 24 May 2024 // 31 May 2024
Paper notification: 3 July 2024 Registration deadline (with application for financial assistance): 18 July 2024
Registration deadline: 28 August 2024
Conference: 1620 September 2024 Update: The submission deadline has been extended to 31st May 2024 for
papers which clearly justify their relevance for the following three
topics: 1) classical causal inference, 2) causality in relativistic physics (including quantum field theory and quantum gravity) and 3) experiments in causality. As we have received a sufficiently high number of submissions on the remaining topics (particularly indefinite causality and quantum causal models), the original deadline of 24th May still holds for submissions in this category. :: :: ::
Call for Abstracts
Prospective speakers can submit a paper for a contributed talk (in person or online) and/or a poster (in person only) via the Call for Abstracts. The Call for Abstracts is now open! Submissions for a talk will automatically be considered for a poster if not accepted for a talk.:: :: ::
Invited Speakers
Jessica Bavaresco (University of Geneva)
Cyril Branciard (CNRS, University Grenoble Alpes)
Rafael Chaves (Federal University of Rio Grande do Norte)
Giulio Chiribella (The University of Hong Kong)
Doreen Fraser (University of Waterloo)
AnneCatherine de la Hamette (IQOQI Vienna)
Ciarán Lee (Spotify)
Tein van der Lugt (University of Oxford)
Joris M. Mooij (University of Amsterdam)
Mio Murao (University of Tokyo)
Alejandro PozasKerstjens (University of Geneva)
Huw Price (Trinity College, Cambridge)
Renato Renner (ETH Zürich)
Thomas Richardson (University of Washington)
Sally Shrapnel (The University of Queensland)
Sumati Surya (Raman Research Institute)
Rainer Verch (University of Leipzig)
:: :: ::
Programme Committee
V Vilasini (ETH Zürich & Inria, University Grenoble Alpes) (PC Chair)
Augustin Vanrietvelde (Télécom Paris) (PC Cochair)
Alastair Abbott (Inria, University Grenoble Alpes)
Časlav Brukner (IQOQI Vienna & University of Vienna)
Eric Cavalcanti (Griffith University)
Chris Fewster (University of York)
Lucien Hardy (Perimeter Institute)
Hlér Kristjánsson (Perimeter Institute & IQC & Université de Montréal)
Giulia Rubino (University of Bristol)
Nitica Sakharwade (Università degli Studi di Napoli Federico II)
Robert Spekkens (Perimeter Institute)
Jacopo Surace (Perimeter Institute)
Elie Wolfe (Perimeter Institute)
LinQing Chen (ETH Zürich & IQOQI Vienna)
Hippolyte Dourdent (ICFO Barcelona)
Tamal Guha (University of Hong Kong)
Robin Lorenz (Quantinuum, Oxford)
Maria Papageorgiou (IQOQI Vienna)
Nicola Pinzani (Université libre de Bruxelles)
MarcoTúlio Quintino (Sorbonne Université, Paris)
MarcOlivier Renou (Inria ParisSaclay & CPHT, École polytechnique)
David Schmid (ICTQT, University of Gdańsk)
John Selby (ICTQT, University of Gdańsk)
Akihito Soeda (National Institute of Informatics, Tokyo)
Matthew Wilson (University College London)
:: :: ::
Scientific Organizers
Hlér Kristjánsson (Perimeter Institute & IQC & Université de Montréal) (Chair)
V Vilasini (ETH Zürich & Inria, University Grenoble Alpes)
Robert Spekkens (Perimeter Institute)
Lucien Hardy (Perimeter Institute)
Elie Wolfe (Perimeter Institute)
Jacopo Surace (Perimeter Institute)
Marina Maciel Ansanelli (Perimeter Institute)
Yìlè Yīng (Perimeter Institute)
María Ciudad Alañón (Perimeter Institute)
Daniel Centeno Díaz (Perimeter Institute)
Khushi Gandhi (Perimeter Institute & University of Waterloo):: :: ::
Previous editions:
Causalworlds 2022: The interface between quantum and relativistic causality, foundations and practicalities
Organised at ETH Zürich in 2022. Website: https://causalworlds.ethz.ch/" 
Quantum Theory (Core), PHYS 605, September 3 – October 4, 2024
14 talksCollection NumberC24036The aim of the first part is to present a brief overview of selected topics in quantum theory. Schrodinger, Heisenberg and Interaction picture is discussed and applied to study time evolution. Density matrix and Feynman path integral are introduced. The second part of the course derives the Feynman rules for scalar quantum field theory and introduces renormalization. Instructor: Bindiya Arora / Dan Wohns Students who are not part of the PSI MSc program should review enrollment and course format information here: https://perimeterinstitute.ca/graduatecourses 
GPTs and the probabilistic foundations of quantum theory  minicourse
7 talksCollection NumberC24021Classical probability theory makes the (mostly, tacit) assumption that any two random experiments can be performed jointly. This assumption seems to fail in quantum theory. A rapidly growing literature seeks to understand QM by placing it in a much broader mathematical landscape of ``generalized probabilistic theories", or GPTs, in which incompatible experiments are permitted. Among other things, this effort has led to (i) a better appreciation that many "characteristically quantum" phenomena (e.g., entanglement) are in fact generic to nonclassical probabilistic theories, (ii) a suite of reconstructions of (mostly, finitedimensional) QM from small packages of assumptions of a probabilistic or operational nature, and (iii) a clearer view of the options available for generalizing QM. This course will offer a survey of this literature, starting from scratch and concluding with a discussion of recent developments.
Mathematical prerequisites: finitedimensional linear algebra, ideally including tensor products and duality, plus some exposure to category theory (though I will briefly review this material as needed).
Scheduling note: There will be 5 lectures from March 1226, then a gap of two weeks before the final 2 lectures held April 16 & 18.
Format: Inperson only; lectures will be recorded for PIRSA but not live on Zoom.


Causal Inference & Quantum Foundations Workshop
26 talksCollection NumberC23017Recently we have seen exciting results at the intersection of quantum foundations and the statistical analysis of causal hypotheses by virtue of the centrality of latent variable models to both fields.
In this workshop we will explore how academics from both sides can move the shared frontiers forward. Towards that end, we are including extensive breakout collaboration opportunities in addition to formal presentations. In order to make concrete progress on problems pertinent to both communities, we have selected the topic of causal models with restricted cardinality of the latent variables as a special focus for this workshop.
Sponsorship for this workshop has been provided by:
Territorial Land Acknowledgement
Perimeter Institute acknowledges that it is situated on the traditional territory of the Anishinaabe, Haudenosaunee, and Neutral peoples.
Perimeter Institute is located on the Haldimand Tract. After the American Revolution, the tract was granted by the British to the Six Nations of the Grand River and the Mississaugas of the Credit First Nation as compensation for their role in the war and for the loss of their traditional lands in upstate New York. Of the 950,000 acres granted to the Haudenosaunee, less than 5 percent remains Six Nations land. Only 6,100 acres remain Mississaugas of the Credit land.
We thank the Anishinaabe, Haudenosaunee, and Neutral peoples for hosting us on their land.

Quantizing Time
36 talksCollection NumberC21004 
Quantum Gravity 2020
22 talksCollection NumberC20031 
Indefinite Causal Structure
26 talksCollection NumberC19049There has been a surge of interest in indefinite causal structure the idea that cause and effect can no longer be sharply distinguished. Motivated both by experimentation with quantum switches and quantum gravity there can be situations in which there is no matterofthefact as to what the causal structure of spacetime is. This meeting will bring together workers in Quantum Foundations and Quantum Gravity in both theoretical experimental physics to discuss the state of the art of current research and set new directions for this emerging subdiscipline.

PSI 2019/2020  Quantum Theory (Branczyk/Dupuis)
14 talksCollection NumberC19038PSI 2019/2020  Quantum Theory (Branczyk/Dupuis) 
Foundations of Quantum Mechanics
17 talksCollection NumberC18020The foundations of quantum mechanics have been revitalized in the past few decades by three developments: (i) the influence of quantum computation and quantum information theory (ii) studies of the interplay between quantum theory and relativity particularly the analysis of indefinite causal structure and (iii) proposals to reconstruct quantum theory from basic axioms. There have also been very interesting developments in understanding and classifying no=locality and contextuality using tools from sheaf theory and cohomology as well as operator algebras and category theory. The International Congress of Mathematical Physics is a natural forum for the discussion of these topics. In the past there have been satellite workshops on topics like Operator algebras and quantum statistical mechanics which also address fundamental issues. The modern study of quantum foundations is very much influenced and informed by mathematics: sheaf theory and cohomology category theory information theory convex analysis in addition to the continuing interest in operator algebras and functional analysis. The aim of the workshop is to bring together researchers who have made substantial contribution to the recent developments. The workshop will be held at Perimeter Institute over a five day period from July 30

Algorithmic Information, Induction and Observers in Physics
17 talksCollection NumberC18007Our universe is of astonishing simplicity: almost all physical observations can in principle be described by a few theories that have short mathematical descriptions. But there is a field of computer science which quantifies simplicity namely algorithmic information theory (AIT). In this workshop we will discuss emerging connections between AIT and physics some of which have recently shown up in fields like quantum information theory and thermodynamics. In particular AIT and physics share one goal: namely to predict future observations given previous data. In fact there exists a gold standard of prediction in AIT called Solomonoff induction which is also applied in artificial intelligence. This motivates us to look at a broader question: what is the role of induction in physics? For example can quantum states be understood as Bayesian states of belief? Can physics be understood as a computation in some sense? What is the role of the observer i.e. the agent that is supposed to perform the predictions? These and related topics will be discussed by a diverse group of researchers from different disciplines.

Observers in Quantum and Foil Theories
11 talksCollection NumberC18006Foil theories sometimes called mathematically rigorous science fiction describe ways the world could have been were it not quantum mechanical. Our understanding of quantum theory has been deepened by contrasting it with these alternatives. So far observers in foil theories have only been modeled implicitly for example via the recorded probabilities of observing events. Even when multiagent settings are considered these agents tend to be compatible in the classical sense that they could always compare their observations. Scenarios where agents and their memories are themselves modeled as physical systems within the theory (and could in particular measure each other as in Wigner's friend experiment) have not yet been considered. In this workshop we will investigate which foil theories allow for the existence of explicit observers and whether they allow for paradoxes in multiagent settings such as those found in quantum theory. We will also investigate which interpretations of quantum theory would equally well interpret the foil theories and which interpretations are truly quantum. We will gain a deeper understanding of how this can happen by discussing appropriate definitions observers in these theories and seeing how such observers learn about their environment.