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

26 talksCollection Number C23017
Talk

Welcome and Opening Remarks
Elie Wolfe Perimeter Institute for Theoretical Physics

Tutorial 1
Robert Spekkens Perimeter Institute for Theoretical Physics

Graphical models: fundamentals, origins, and beyond
Steffen Lauritzen University of Copenhagen

Towards standard imsets for maximal ancestral graphs
Robin Evans University of Oxford


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



Quantizing Time
36 talksCollection Number C21004Talk

Welcome and Opening Remarks

Alexander Smith Dartmouth College

Flaminia Giacomini ETH Zurich



KappaMinkowski: physics with noncommutative time
Flavio Mercati University of Naples Federico II

Quantizing causation
Robert Spekkens Perimeter Institute for Theoretical Physics

Noncausal PageWootters circuits
Veronika Baumann Institute for Quantum Optics and Quantum Information (IQOQI)  Vienna

Quantum reference frames for space and spacetime
Časlav Brukner Vienna Center for Quantum Science and Technology


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


Quantum Gravity 2020
22 talksCollection Number C20031Talk

Welcome and Opening Remarks
Bianca Dittrich Perimeter Institute for Theoretical Physics

Approaches to Quantum Gravity: Key Achievements and Open Issues
Hermann Nicolai MaxPlanckInstitut für Gravitationsphysik

Quantum gravity from the loop perspective
Alejandro Perez Centre de Physique Théorique

Lessons for quantum gravity from quantum information theory
Daniel Harlow Massachusetts Institute of Technology (MIT)

Understanding of QG from string theory
Herman Verlinde Princeton University

Progress in horizon thermodynamics
Aron Wall University of Cambridge

Asymptotically Safe Amplitudes from the Quantum Effective Action
Frank Saueressig Radboud Universiteit Nijmegen

The Remarkable Roundness of the Quantum Universe
Renate Loll Radboud Universiteit Nijmegen


Indefinite Causal Structure
26 talksCollection Number C19049Talk


10 years of the quantum SWITCH: state of the art and new perspectives
Giulio Chiribella The University of Hong Kong (HKU)

Cyclic quantum causal models and violations of causal inequalities
Ognyan Oreshkov Université Libre de Bruxelles

TBA
Laura Henderson University of Waterloo

Composing causal orderings
Aleks Kissinger University of Oxford

Quantum principle of relativity
Andrzej Dragan University of Warsaw


What happens when we quantize time?
Alexander Smith Dartmouth College


PSI 2019/2020  Quantum Theory (Branczyk/Dupuis)
14 talksCollection Number C19038Talk








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


Foundations of Quantum Mechanics
17 talksCollection Number C18020Talk

Welcome and Opening Remarks
Lucien Hardy Perimeter Institute for Theoretical Physics



Local quantum operations and causality
Robert Oeckl Universidad Nacional Autónoma De Mexico (UNAM)

Towards synthetic Euclidean quantum field theory
Tobias Fritz Universität Innsbruck

Almost quantum correlations violate the norestriction hypothesis
Ana Belen Sainz Gdańsk University of Technology

A deviceindependent approach to testing physical theories from finite data
YeongCherng Liang National Cheng Kung University

Quantum axiomatics à la carte
Alexander Wilce Susquehanna University


Algorithmic Information, Induction and Observers in Physics
17 talksCollection Number C18007Talk


Quantum speedup in testing causal hypotheses
Giulio Chiribella The University of Hong Kong (HKU)

The Logic of Physical Law
Stefan Wolf Universit della Svizzera italiana


On the concepts of universality in physics and computer science
Gemma De Las Cuevas Universität Innsbruck

A nogo theorem for observerindependent facts
Časlav Brukner Vienna Center for Quantum Science and Technology


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


Observers in Quantum and Foil Theories
11 talksCollection Number C18006Talk

Wavefunction branches as a foundation for constructing foil theories
Jess Riedel NTT Research
PIRSA:18040082 
Compatibility of implicit and explicit observers in quantum theory and beyond
Thomas Galley Institute for Quantum Optics and Quantum Information (IQOQI)  Vienna
PIRSA:18040084 
From observers to physics via algorithmic information theory I
Markus Müller Institute for Quantum Optics and Quantum Information (IQOQI)  Vienna
PIRSA:18040078 
From observers to physics via algorithmic information theory II
Markus Müller Institute for Quantum Optics and Quantum Information (IQOQI)  Vienna
PIRSA:18040080 
Motility of the internalexternal cut as a foundational principle
Robert Spekkens Perimeter Institute for Theoretical Physics
PIRSA:18040073 

Quantum theory cannot consistently describe the use of itself
Renato Renner ETH Zurich  Institut für Theoretische Physik
PIRSA:18040085 


Lecture Series on Operational General Relativity
6 talksCollection Number C17054Talk

Operational General Relativity  Lecture 1
Lucien Hardy Perimeter Institute for Theoretical Physics

Operational General Relativity  Lecture 2
Lucien Hardy Perimeter Institute for Theoretical Physics

Operational General Relativity  Lecture 3
Lucien Hardy Perimeter Institute for Theoretical Physics

Operational General Relativity  Lecture 4
Lucien Hardy Perimeter Institute for Theoretical Physics

Operational General Relativity  Lecture 5
Lucien Hardy Perimeter Institute for Theoretical Physics

Operational General Relativity  Lecture 6
Lucien Hardy Perimeter Institute for Theoretical Physics


Talk

Semisimple Hopf algebras and fusion categories
Cesar Galindo Universidad de los Andes

The Hopf C*algebraic quantum double models  symmetries beyond group theory
Andreas Bauer Freie Universität Berlin

Modular categories and the Witt group
Michael Mueger Radboud Universiteit Nijmegen

Topological Quantum Computation
Eric Rowell Texas A&M University

Gapped phases of matter vs. Topological field theories
Davide Gaiotto Perimeter Institute for Theoretical Physics

An Introduction to Hopf Algebra Gauge Theory
Derek Wise FriedrichAlexanderUniversität ErlangenNürnberg

Kitaev lattice models as a Hopf algebra gauge theory
Catherine Meusburger University of ErlangenNuremberg

Topological defects and highercategorical structures
Jurgen Fuchs Karlstad University


Contextuality: Conceptual Issues, Operational Signatures, and Applications
23 talksCollection Number C17027Talk

Welcome and Opening Remarks
Robert Spekkens Perimeter Institute for Theoretical Physics

Quantum Mechanics in a New Key
Simon Kochen Princeton University

What do we learn about quantum theory from KochenSpecker quantum contextuality?
Adan Cabello Universidad de Sevilla

Noncontextuality: how we should define it, why it is natural, and what to do about its failure
Robert Spekkens Perimeter Institute for Theoretical Physics

Towards a mathematical theory of contextuality
Samson Abramsky University of Oxford

KochenSpecker contextuality: a hypergraph approach with operational equivalences
Ana Belen Sainz Gdańsk University of Technology

The contextual fraction as a measure of contextuality
Shane Mansfield University of Edinburgh

Nonlocality and contextuality as finetuning
Eric Cavalcanti Griffith University


Experimental Quantum Foundations
5 talksCollection Number C16034Talk

Direct experimental reconstruction of the Bloch sphere

Michael Mazurek Institute for Quantum Computing (IQC)

Matthew Pusey University of York


Singlephoton test of HyperComplex Quantum Theories
Lorenzo Procopio Universität Wien



Experimental implementation of quantumcoherent mixtures of causal relations
Robert Spekkens Perimeter Institute for Theoretical Physics


Causal Inference & Quantum Foundations Workshop
26 talksCollection Number C23017Recently 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 Number C21004 
Quantum Gravity 2020
22 talksCollection Number C20031 
Indefinite Causal Structure
26 talksCollection Number C19049There 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 Number C19038PSI 2019/2020  Quantum Theory (Branczyk/Dupuis) 
Foundations of Quantum Mechanics
17 talksCollection Number C18020The 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 Number C18007Our 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 Number C18006Foil 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.

Lecture Series on Operational General Relativity
6 talksCollection Number C17054Lecture Series on Operational General Relativity 
Hopf Algebras in Kitaev's Quantum Double Models: Mathematical Connections from Gauge Theory to Topological Quantum Computing and Categorical Quantum Mechanics
18 talksCollection Number C17029The Kitaev quantum double models are a family of topologically ordered spin models originally proposed to exploit the novel condensed matter phenomenology of topological phases for faulttolerant quantum computation. Their physics is inherited from topological quantum field theories, while their underlying mathematical structure is based on a class of Hopf algebras. This structure is also seen across diverse fields of physics, and so allows connections to be made between the Kitaev models and topics as varied as quantum gauge theory and modified strong complementarity. This workshop will explore this shared mathematical structure and in so doing develop the connections between the fields of mathematical physics, quantum gravity, quantum information, condensed matter and quantum foundations.

Contextuality: Conceptual Issues, Operational Signatures, and Applications
23 talksCollection Number C170272017 marks 50 years since the seminal 1967 article of Kochen and Specker proving that quantum theory fails to admit of a noncontextual model. Despite the fact that the KochenSpecker theorem is one of the seminal results concerning the foundations of quantum theory, there has never been a large conference dedicated to the subject. The 50year anniversary of the theorem seems an opportune time to remedy this oversight. Furthermore, in the last decade, there have been tremendous advances in the field. New life has been breathed into the subject as old conceptual issues have been reexamined from a new informationtheoretic perspective. Importantly, there has been great progress in making the notion of noncontextuality robust to noise and therefore experimentally testable. Finally, there is mounting evidence that the resource that powers many quantum advantages for information processing is contextuality. In particular, it has been shown to underlie the possibility of universal quantum computation. Many groups worldwide are actively engaged in advancing our knowledge on each of these fronts and in deepening our understanding of the distinction between quantum and classical theories through the lens of contextuality. Through this conference, we aim to bring together leading researchers in the field in order to develop a broader perspective on the issues, draw connections between different approaches, foster a more cohesive community, and set objectives for future research.

Experimental Quantum Foundations
5 talksCollection Number C16034Experimental Quantum Foundations