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

7 talksCollection Number C24036
Talk

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

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

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

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

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

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

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


GPTs and the probabilistic foundations of quantum theory  minicourse
7 talksCollection Number C24021Talk

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

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

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

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

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

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

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


Quantum Foundations
13 talksCollection Number C24008Talk

Quantum Foundations Lecture
Lucien Hardy Perimeter Institute for Theoretical Physics

Quantum Foundations Lecture
Lucien Hardy Perimeter Institute for Theoretical Physics

Quantum Foundations Lecture
Lucien Hardy Perimeter Institute for Theoretical Physics

Quantum Foundations Lecture
Lucien Hardy Perimeter Institute for Theoretical Physics

Quantum Foundations Lecture
Lucien Hardy Perimeter Institute for Theoretical Physics

Quantum Foundations Lecture
Lucien Hardy Perimeter Institute for Theoretical Physics

Quantum Foundations Lecture
Lucien Hardy Perimeter Institute for Theoretical Physics

Quantum Foundations Lecture
Lucien Hardy Perimeter Institute for Theoretical Physics


Causal Inference & Quantum Foundations Workshop
26 talksCollection Number C23017Talk

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 Saint Anselm 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 Institute for Quantum Optics and Quantum Information (IQOQI)  Vienna


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 AixMarseille University

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 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 Saint Anselm 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 University of Hong Kong (HKU)

The Logic of Physical Law
Stefan Wolf Università 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 Institute for Quantum Optics and Quantum Information (IQOQI)  Vienna


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
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


Quantum Theory (Core), PHYS 605, September 3 – October 4, 2024
7 talksCollection Number C24036The 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 Number C24021Classical 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 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