List of talks organised by speaker

We currently have videos of 59 talks by 46 different speakers.

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# Samson Abramsky, University of Oxford

Categorical quantum mechanics: The "monoidal" approach
January 2008, Categories, Logic and Foundations of Physics I
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Information flow in physics, geometry, logic and computation V: A tale of dependence and separation
March 2008, Clifford Lectures 2008
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# Howard Barnum, Los Alamos National Laboratory

(No title)
March 2008, Logic, Physics and Quantum Information Theory
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# John Barrett, University of Nottingham

Knots and links in braided quantum field theory
August 2008, Categories, Logic and Foundations of Physics III
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I will explain some aspects of braided quantum field theory: how it is a generating function of knots and links, and also a little about the relation to 3d quantum gravity.

# Bruce Bartlett, University of Sheffield

Aspects of duality in 2-categories
May 2008, Categories, Logic and Foundations of Physics II
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The notion of ‘duality’ plays an important role in quantum algebra and topological quantum field theory, as has been particularly emphasized by Baez and Dolan. One aspect of this is the idea of duals for morphisms in a 2-category, which is a generalization of the idea of rigidity in monoidal categories. I will introduce the notion of an ‘even-handed structure’ on a 2-category as a coherent means of turning right adjoints into left adjoints, and explain how this works in various examples such as fusion categories, braided monoidal categories, 2-Hilbert spaces and derived categories having a ‘trivial Serre functor’.

# Luca Bernardinello, University of Milan-Biocca

On orthomodular posets generated by transition systems
July 2008, Quantum Physics and Logic 2008
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# Paolo Bertozzini, Thammasat University

Categories of spectral geometries
May 2008, Categories, Logic and Foundations of Physics II
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In A. Connes' non-commutative geometry, "spaces" are described "dually" as spectral triples. We provide an overview of some of the notions that we deem necessary for the development of a categorical framework in the context of spectral geometry, namely: (a) several notions of morphism of spectral geometries, (b) a spectral theory for commutative full C*-categories, (c) a tentative definition of strict-n-C*-categories, (d) spectral geometries over C*-categories. If time will allow, we will speculate on possible applications to foundational issues in quantum physics: categorical covariance, spectral quantum space-time and modular quantum gravity.

# Edward Blakey, University of Oxford

Computational complexity in non-Turing models of computation: the what, the why and the how
July 2008, Quantum Physics and Logic 2008
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# Dan Browne, University College London

Measurement-based quantum computation
March 2008, Logic, Physics and Quantum Information Theory
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# Eugenia Cheng, University of Sheffield

The periodic table of n-categories
January 2009, Categories, Logic and Foundations of Physics IV
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Degenerate n-categories are those whose lowest k dimensions are trivial, for some k>0. These can be thought of as the categorical analogue of loop spaces. The resulting multiplicative structures are interesting in their own right, and fit into a table known as the ''periodic table of n-categories''. The table has various interesting patterns observable in low-dimensions and conjectured in general by Baez and Dolan. The structures that arise in this way include monoids and commutative monoids, as well as monoidal, braided, and symmetric monoidal categories. We will outline the main ideas behind the Periodic Table, its patterns and predictions, including the crucial stabilisation property which lead Baez and Dolan to conjecture a beautiful universal property to characterise higher-dimensional tangles. The talk will be introductory, in some sense a sequel to Tom Leinster's introduction to n-categories that precedes it. Beyond this no knowledge of n-categories will be assumed.

# Bob Coecke, University of Oxford

A survey of categorical quantum mechanics
March 2008, Logic, Physics and Quantum Information Theory
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Tutorial: the quantum formalism
August 2008, Categories, Logic and Foundations of Physics III
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Classical versus quantum — in pictures
March 2008, Clifford Lectures 2008
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# Louis Crane, Kansas State University

Relational topology and quantum gravity
January 2008, Categories, Logic and Foundations of Physics I
Video
We explore arguments for replacing the absolute point set by a sheaf over the site of observation as a foundation for quantum gravity. Time permitting, we consider apparent geometry as a formulation for relational geometry.

Model categories in quantum gravity
August 2008, Categories, Logic and Foundations of Physics III
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We examine a plausible physical hypothesis which would allow us to model quantum regions as differential graded Hopf algebras or as differential graded categories.

# Yannick Delbecque, McGill University

Quantum higher types
July 2008, Quantum Physics and Logic 2008
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# Ellie D'Hondt, Free University of Brussels

Classical knowledge for quantum security
July 2008, Quantum Physics and Logic 2008
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# Andreas Doering, Imperial College London

Tutorial: conceptual issues in quantum theory
August 2008, Categories, Logic and Foundations of Physics III
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# Fay Dowker, Imperial College London

Dynamical logic
May 2008, Categories, Logic and Foundations of Physics II
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Despite the high regard in which physicists hold General Relativity, the spacetime nature of reality has not yet fully been taken to heart in addressing the question of the interpretation of quantum mechanics. Partial progress was made by Dirac and Feynman by casting the dynamical content of quantum theory in terms of a Sum Over (spacetime) Histories (SOH). Recently it has been suggested that this SOH is part of an interpretive framework in which the rules of inference that are used to reason about physical reality are themselves subject to dynamical law. Just as General Relativity showed that geometry is not fixed and absolute, so Quantum Mechanics may be telling us that “logic” is not a fixed background but part of physics.

# Ross Duncan, University of Oxford

Classical structures, MUBs, and pretty pictures
January 2008, Categories, Logic and Foundations of Physics I
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The logic of complementary observables
March 2008, Clifford Lectures 2008
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Interacting quantum observables
July 2008, ICALP 2008
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# Bill Edwards, University of Oxford

Toy quantum categories
July 2008, Quantum Physics and Logic 2008
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# Jeff Egger, University of Edinburgh

Monoidal categories and enriched dagger categories
, Seminars
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# Chris Fewster, University of York

The locally covariant approach to quantum field theory in curved spacetimes
August 2008, Categories, Logic and Foundations of Physics III
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A long-established guiding principle for quantum field theory in curved spacetimes is that it should be formulated in a local and geometrically covariant way. Recently, Brunetti, Fredenhagen and Verch have given an elegant formulation of this principle in categorical terms: a theory should be understood as a functor from a category of spacetimes to a category of star-algebras. This conceptual clarification is at the heart of a number of important results for QFT in general spacetimes, such as a proof of the spin-statistics theorem and the perturbative construction of interacting QFT. This talk reviews the locally covariant approach and some of its applications, and also describes joint work with Verch that refines and sharpens the framework.

# Jonathan Grattage, University of Grenoble

QML in 15 minutes
July 2008, Quantum Physics and Logic 2008
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# Keith Hannabuss, University of Oxford

Categories and non-associative C*-algebras in quantum field theory
August 2008, Categories, Logic and Foundations of Physics III
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# Lucien Hardy, Perimeter Institute

The causaloid approach to quantum theory and quantum gravity
March 2008, Logic, Physics and Quantum Information Theory
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Quantum theory is probabilistic but has fixed causal structure. General relativity is deterministic but has non-fixed causal structure. It seems that a theory of quantum gravity will inherit the radical features of these two less fundamental theories. Thus, we expect it to be probabilistic and have non-fixed causal structure. In this talk I present a framework, the causaloid formalism, for such theories.

# Chris Heunen, University of Nijmegen

A topos for algebraic quantum theory
January 2008, Categories, Logic and Foundations of Physics I
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Motivated by Bohr's idea that the empirical content of quantum physics is accessible only through classical physics, we show how a C*-algebra A induces a topos in which the amalgamation of all its commutative subalgebras comprises a single commutative C*-algebra. According to the constructive Gelfand duality theorem of Banaschewski and Mulvey, the latter has an internal spectrum X in the topos, which plays the role of a quantum phase space of the system. States on A become probability integrals on X, and self-adjoint elements of A define functions from X to the pertinent internal real numbers (the interval domain), allowing for a state-proposition pairing. Thus the quantum theory defined by A is turned into a classical theory by restriction to its associated topos.

# Basil Hiley, Birkbeck College London

Towards a quantum geometry: groupoids, Clifford algebras and shadow manifolds
May 2008, Categories, Logic and Foundations of Physics II
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I will present some ideas, which although not yet formulated in terms of categories, uses the spirit of category theory especially as articulated by Lawvere. Starting from first principles, I follow Kauffman in making distinctions between two aspects of each indivisible sub-process and then order these processes to form a groupoid, which is then generalised into what I call an algebra of process. The resulting algebra is shown to be isomorphic to a hierarchy of orthogonal Clifford algebras, which, of course, include the Pauli and Dirac algebras. I then exploit the minimal left and right ideals to map from the algebra of process to a vector space inducing a light cone structure thus inverting the usual approach since here the vector space inherits its structure from the fundamental processes. Although I am working with the algebra of process, all of this is still within the conceptual framework used by Clifford himself, namely, classical physics. I then present an argument to generalise this structure to include symplectic Clifford algebras enabling us to introduce the Heisenberg group. Using the techniques applied to orthogonal CAs, I am able to show that the idempotents of this algebra map onto the points of an underlying manifold. Since the symplectic group acts in (x, p) phase space algebra, quantum mechanics demands that this structure is non-commutative and it is this feature that produces shadow manifolds. I will discuss the significance of these results.

# Chris Isham, Imperial College London

Topos theory in the formulation of theories of physics
January 2008, Categories, Logic and Foundations of Physics I
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# Peter Johnstone, University of Cambridge

Topos-theoretic models of the continuum
May 2008, Categories, Logic and Foundations of Physics II
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We survey a number of different approaches to modelling the continuum in a topos, with particular reference to such questions as whether the real line should be viewed as a space or a locale, the ring-theoretic properties of the continuum, and whether it is sensible to require that all real functions should be continuous or even smooth.

# Tom Leinster, University of Glasgow

An introduction to n-categories
January 2009, Categories, Logic and Foundations of Physics IV
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I will give an beginners' introduction to n-categories. First I'll explain roughly what an n-category is, and talk about some of the dreams that first led people to want to develop a theory of n-categories. Then I'll go into more detail, leading up to a description of the state of the art and of some of the difficulties involved in trying to make those dreams come true. This is a completely introductory talk, for those who know nothing about n-categories. Experts will be bored senseless.

# Lorenzo Maccone, University of Pavia

A quantum solution to the arrow-of-time dilemma
July 2008, Quantum Physics and Logic 2008
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# Keye Martin, Naval Research Laboratory

The mechanics of information
March 2008, Logic, Physics and Quantum Information Theory
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Domain theory and the causal structure of spacetime II
March 2008, Clifford Lectures 2008
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A domain-theoretic model of qubit channels
July 2008, ICALP 2008
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How to randomly flip a quantum bit
July 2008, Quantum Physics and Logic 2008
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# Paul-André Melliès, Université Paris Diderot

Quantum groupoids and logical dualities
May 2008, Categories, Logic and Foundations of Physics II
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# Ieke Moerdijk, Utrecht University

Infinity categories and infinity operads
January 2009, Categories, Logic and Foundations of Physics IV
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We discuss some aspects of the simplicial theory of infinity-categories which originates with Boardman and Vogt, and has recently been developed by Joyal, Lurie and others. The main purpose of the talk will be to present an extension of this theory which covers infinity-operads. It is based on a modification of the notion of simplicial set, called “dendroidal set”. One of the main results is that the category of dendroidal sets carries a monoidal Quillen model structure, in which the fibrant objects are precisely the infinity-operads, and which contains the Joyal model structure for infinity-categories as a localization. The lecture is partly based on joint work with Ittay Weiss, Clemens Berger, and Denis-Charles Cisinski.

# Prakash Panangaden, McGill University

The physics of anyons for computer scientists
March 2008, Logic, Physics and Quantum Information Theory
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I give a simple account of the Hall effect and the quantum Hall effect. I give a short account of the spin-statistics theorem and the changes that happen in 2 dimensions which allows for the appearance of anyons.

Domain theory and the causal structure of spacetime I
March 2008, Clifford Lectures 2008
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# Éric Paquette, McGill University

Categories and quantum computating with anyons
March 2008, Logic, Physics and Quantum Information Theory
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During this talk I will present the categorical structures necessary to describe anyons; more precisely, the structures that capture the concepts of charges, braids, twist and fusion rules together with the way these structures are used to translate the kinematics of the anyons into the Hilbert space language used to describe quantum computation. We will also present one of the simplest models of non-abelian anyons, the Fibonacci anyons, and explain how to build a set of gates which is universal for quantum computation within this model.

Topological quantum computing with anyons
January 2009, Categories, Logic and Foundations of Physics IV
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In nature one observes that in three space dimensions particles are either symmetric or antisymmetric under interchange. In two dimensions, however, a whole continuum of phases is possible; "Anyon" is a term that describes quasi-particles in 2 dimensions that can acquire any phase when two or more of them are interchanged. Such peculiar property permits one to encode information in topological features of a system composed of many anyons. It has been suggested that such topological excitations could be used for robust quantum computation.

# Simone Perdrix, University of Oxford

Bases in diagrammatic quantum protocols
August 2008, Categories, Logic and Foundations of Physics III
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Partial observation of quantum Turing machine and weaker well-formedness condition
July 2008, Quantum Physics and Logic 2008
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# Terry Rudoloph, Imperial College London

Quantum computing, matrix permanents and why Bob Coecke isn't the only person who gets to do quantum mechanics by drawing trivial-looking graphs
July 2008, Quantum Physics and Logic 2008
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What is the vector space content of what we say? … a categorical approach to distributed meaning
August 2008, Categories, Logic and Foundations of Physics III
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# Peter Selinger, Dalhousie University

Finite-dimensional Hilbert spaces are complete for dagger compact closed categories
July 2008, Quantum Physics and Logic 2008
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# Rob Spekkens, University of Cambridge

The power of epistemic restrictions in axiomatizing quantum theory: from trits to qutrits
, Seminars
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It is common to assert that the discovery of quantum theory overthrew our classical conception of nature. But what, precisely, was overthrown? Providing a rigorous answer to this question is of practical concern, as it helps to identify and analyze quantum technologies that outperform their classical counterparts. It is also of significance for modern physics, where the challenge of applying quantum theory in new realms or moving beyond quantum theory necessitates a deep understanding of the principles upon which it is based. In this talk, I demonstrate that a large part of quantum theory can be obtained from a single innovation relative to classical theories, namely, that there is a fundamental restriction on the sorts of statistical distributions over classical states that can be prepared. This restriction implies a fundamental limit on the amount of knowledge that any observer can have about the classical state. I will consider in particular the case of an arbitrary number of 3-state classical systems, or trits, and I will show that using a particular sort of statistical restriction that appeals to the symplectic structure of the classical state space, one can reproduce the predictions of the stabilizer formalism for qutrits. I will end with a few speculations about the conceptual innovations that might underlie phenomena that can't be derived from a statistical restriction and what might be the origin of the restriction.

# Isar Stubbe, University of Antwerp

Principally-generated modules on a quantale
January 2009, Categories, Logic and Foundations of Physics IV
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Let $Q$ be a quantale, and $\rm{Mod}(Q)$ the locally ordered category of $Q$-modules and $Q$-module morphisms. Using splittings of idempotents and adjunctions in $\rm{Mod}(Q)$, I shall define the 'principal elements' of a given $Q$-module; a 'principally generated' $Q$-module is then one "with enough principal elements". Applying this to a module over the two-element chain, i.e. a complete lattice, will give a familiar notion. I shall explain how, in general, this is related to the theory of ordered (!) sheaves over $Q$. When $Q$ is moreover involutive, it makes sense to speak of ‘principally symmetric’ $Q$-modules; this then is related to sheaves over $Q$. Time permitting, I shall say a word or two on 'Hilbert $Q$-modules' too.

# Benoit Valiron, University of Ottawa

On quantum and probabilistic linear lambda calculi
July 2008, Quantum Physics and Logic 2008
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# Jamie Vicary, University of Oxford

A categorical framework for the quantum harmonic oscillator
January 2008, Categories, Logic and Foundations of Physics I
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I will describe a categorical approach to the construction of symmetric Fock space, the state space of the quantum harmonic oscillator. Many of the conventional mathematical tools used to study this system — such as raising and lowering operators, and coherent states — emerge naturally from the category theory, and satisfy the usual equations. However, the formalism is more general than the conventional approach, and I will describe how to construct an infinite variety of 'exotic' Fock spaces. I will finish with the question: "Where has the 'quantumness' come from?"

Categorical formulation of finite-dimensional C*-algebras
July 2008, Quantum Physics and Logic 2008
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I describe how dagger-Frobenius monoids in the category of finite-dimensional Hilbert spaces are the same as finite-dimensional C*-algebras.

# Steve Vickers, Imperial College London

Locales via bundles
August 2008, Categories, Logic and Foundations of Physics III
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Locale theory, a "point-free" approach to topology, can be understood as viewing topological spaces as the spaces of models for logical theories of a particular kind. It has been found effective in a variety of fields, including pure mathematics (deriving from algebraic geometry) and computer science (notably in Abramsky's thesis). One of its most compelling virtues is that it interacts well with constructive mathematics, including the internal mathematics of toposes. In fact, it has a more satisfactory body of constructively valid results than does ordinary point-set topology. Locales have also appeared in the topos approaches to quantum mechanics of Isham and Doering at Imperial and (more explictly) of Heunen, Landsman and Spitters at Nijmegen. Locales have been motivated in a variety of ways, but the path to the constructive virtues can be long and stony. I shall outline a conceptual development in terms of bundles, and going back to a technical result described by Joyal and Tierney in 1984 and known even earlier. Essentially it says that bundles over a space X are equivalent to topological spaces in the internal mathematics of "bundles of sets" (local homeomorphisms) over X. This fits an intuition that "bundle" means a space (the fibre) parametrized by points of the base space. However, there are simple examples to show that this cannot work with a point-set approach to topology - essentially because arbitrary bundles cannot be approximated closely enough by local homeomorphisms. Instead, spaces must be replaced by locales. A key notion is that of "geometric" reasoning, preserved under pullback of bundles, that is more restricted than topos-valid reasoning. It is hoped that the topos-internal reasoning of the Imperial and Nijmegen groups, insofar as it is geometric, can be expressed more intuitively as fibrewise reasoning for bundles.

# Alex Wilce, Susquehanna University

Information processing in convex operational theories: cloning, broadcasting, information-disturbance, bit commitment
July 2008, Quantum Physics and Logic 2008
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# Simon Willerton, University of Sheffield

Two 2-traces
August 2008, Categories, Logic and Foundations of Physics III
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In a monoidal category there is a notion of a trace for certain types of endomorphisms — for example the trace of an endomorphism of a finite dimensional vector space. In a monoidal bicategory there are two different notions of trace for endomorphisms which in various cases are 'dual'; I will describe these traces diagrammatically. Several examples from assorted areas will be given and I hope that the audience will come up with some more.

# Andreas Winter, Bristol University

The mother of all protocols: quantum coding for dummies
July 2008, Quantum Physics and Logic 2008
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# Jon Yard, Caltech

(No title)
March 2008, Logic, Physics and Quantum Information Theory
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