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

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 University of ErlangenNuremberg

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 University of Vienna



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


Formulating and Finding HigherOrder Interference
9 talksCollection Number C16018Talk




Does relativistic causality constrain interference phenomena?
Markus Müller Institute for Quantum Optics and Quantum Information (IQOQI)  Vienna






Time in Cosmology
14 talksCollection Number C16016Talk

Welcome and Opening Remarks

Marina Cortes Institute for Astrophysics and Space Sciences

Lee Smolin Perimeter Institute for Theoretical Physics

Neil Turok University of Edinburgh



The origin of arrows of time II

Sean Carroll California Institute of Technology (Caltech)  Division of Physics Mathematics & Astronomy

Marina Cortes Institute for Astrophysics and Space Sciences

Tim Koslowski Technical University of Applied Sciences WürzburgSchweinfurt


The origin of arrows of time II cont.

Sean Carroll California Institute of Technology (Caltech)  Division of Physics Mathematics & Astronomy

Marina Cortes Institute for Astrophysics and Space Sciences

Tim Koslowski Technical University of Applied Sciences WürzburgSchweinfurt


Testing time asymmetry in the early universe

Brian Keating University of California, San Diego

Andrew Liddle University of Lisbon

Richard Muller University of California, Berkeley


The fate of the big bang

Abhay Ashtekar Pennsylvania State University

Neil Turok University of Edinburgh


Time as Organization – Downward Caustation, Structure and Complexity I
Barbara Drossel Technische Universität Darmstadt

Time as Organization – Downward Caustation, Structure and Complexity II

Stuart Kauffman Santa Fe Institute

George Ellis University of Cape Town



Concepts and Paradoxes in a Quantum Universe
44 talksCollection Number C16015Talk


Finally making sense of Quantum Mechanics, part 1
Yakir Aharonov Chapman University

How to count one photon and get a(n average) result of 1000...
Aephraim Steinberg University of Toronto


The Quantum Tip of the TwoVector Iceberg
Avshalom Elitzur Israeli Institute for Advanced Research

The arrow of time for continuous quantum measurements
Andrew Jordan University of Rochester

Observation of AharonovBohm effect with quantum tunneling
Yutaka Shikano Institute for Molecular Science, National Institutes of Natural Sciences



Concepts and Paradoxes
11 talksCollection Number C16008Talk






Sudden Sharp Forces and Nonlocal Interactions
Yakir Aharonov Chapman University

Protective Measurement and Ergodicity
Yakir Aharonov Chapman University



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

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 
Formulating and Finding HigherOrder Interference
9 talksCollection Number C16018Formulating and Finding HigherOrder Interference


Concepts and Paradoxes in a Quantum Universe
44 talksCollection Number C16015Concepts and Paradoxes in a Quantum Universe


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

Partitions in quantum theory
Augustin Vanrietvelde Télécom Paris
The standard perspective on subsystems in quantum theory is a bottomup, compositional one: one starts with individual "small" systems, viewed as primary, and composes them together to form larger systems. The topdown, decompositional perspective goes the other way, starting with a "large" system and asking what it means to partition it into smaller parts. In this talk, I will 1/ argue that the adoption of the topdown perspective is the key to progress in several current areas of foundational research; and 2/ present an integrated mathematical framework for partitions into three or more subsystems, using subC* algebras. Concerning the first item, I will explain how the topdown perspective becomes crucial whenever the way in which a quantum system is partitioned into smaller subsystems is not unique, but might depend on the physical situation at hand. I will display how that precise feature lies at the heart of a flurry of current hot foundational topics, such as quantum causal models, Wigner's friend scenarios, superselection rules, quantum reference frames, and debates over the implementability of the quantum switch. Concerning the second item, I will argue that partitions in (finitedimensional) quantum theory can be naturally pinned down using subC* algebras. Building on simple illustrative examples, I will discuss the oftenoverlooked existence of nonfactor C*algebras, and how it leads to numerous subtleties  in particular a generic failure of local tomography. I will introduce a sound framework for quantum partitions that overcomes these challenges; it is the first topdown framework that allows to consider three or more subsystems. Finally, as a display of this framework's technical power, I will briefly present how its application to quantum causal modelling unlocked the proof that all 1D quantum cellular automata admit causal decompositions.
(This is joint work with Octave Mestoudjian and Pablo Arrighi. This talk is complementary to my Causalworlds 2024 presentation, which will focus on the issue of causal decompositions.)

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