Colloquium

609 talks

S001

Collection TypeSeries

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Displaying 325 - 336 of 609

Quantum thermalization and many-body Anderson localization

David Huse Princeton University
April 30, 2014

PIRSA:14040066
Quantum Foundations
Conformal Standard Model

Krzysztof Meissner University of Warsaw

April 23, 2014

PIRSA:14040061
Exact Classical Simulation of the Quantum-Mechanical GHZ Distribution

Gilles Brassard Université de Montréal
April 16, 2014

PIRSA:14040060
Quantum Information
The computational power of quantum walk

Andrew Childs University of Waterloo

April 11, 2014

PIRSA:14040135
Almost quantum correlations

Antonio Acin Institute of Photonic Sciences (ICFO)

April 09, 2014

PIRSA:14040065
Scribble, Scribble

Isabella Stefanescu

April 02, 2014

PIRSA:14040117
Effective field theory for hydrodynamical systems

Alberto Nicolis Columbia University
March 28, 2014

PIRSA:14030121
Quantum Fields and Strings

Cosmology
The invasion of physics by information theory

Robert Spekkens Perimeter Institute for Theoretical Physics
March 26, 2014

PIRSA:14030085
Quantum Foundations
Exact results in supersymmetric gauge theories in various dimensions

Sara Pasquetti University of Milan
March 19, 2014

PIRSA:14030084
Particle Physics
Black Holes- the Harmonic Oscillators of the 21st Century

Andrew Strominger Harvard University
March 12, 2014

PIRSA:14030104
Quantum Fields and Strings
The Unreasonable Effectiveness Of Quantum Physics in Modern Mathematics

Robbert Dijkgraaf Institute for Advanced Study (IAS)
March 05, 2014

PIRSA:14030083
Mathematical physics
À la recherche du temps perdu - Templeton Frontiers Colloquia

Flavio Mercati University of Naples Federico II
February 26, 2014

PIRSA:14020100
Quantum Gravity

Quantum thermalization and many-body Anderson localization

David Huse Princeton University
April 30, 2014

PIRSA:14040066
Quantum Foundations
Progress in physics and quantum information science motivates much recent study of the behavior of strongly-interacting many-body quantum systems fully isolated from their environment, and thus undergoing unitary time evolution. What does it mean for such a system to go to thermal equilibrium? I will explain the Eigenstate Thermalization Hypothesis (ETH), which posits that each individual exact eigenstate of the system's Hamiltonian is at thermal equilibrium, and which appears to be true for most (but not all) quantum many-body systems. Prominent among the systems that do not obey this hypothesis are quantum systems that are many-body Anderson localized and thus do not constitute a reservoir that can thermalize itself. When the ETH is true, one can do standard statistical mechanics using the `single-eigenstate ensembles', which are the limit of the microcanonical ensemble where the `energy window' contains only a single many-body quantum state. These eigenstate ensembles are more powerful than the traditional statistical mechanical ensembles, in that they can also "see" the quantum phase transition in to the localized phase, as well as a rich new world of phases and phase transitions within the localized phase.
Conformal Standard Model

Krzysztof Meissner University of Warsaw

April 23, 2014

PIRSA:14040061

I will describe a proposal of an enlargement of the Standard Model based on a softly broken conformal symmetry. It contains the usual particles of the SM with right-chiral neutrinos and predicts two new particles: a scalar mixing with the usual Higgs and a naturally weakly coupled axion. I will argue that the Planck scale should be treated as a real physical scale and discuss the hierarchy problem and renormalization from this point of view. I will show that the model does not need any intermediate scales and can be viable up to the Planck scale (in distiction to the Standard Model). I will present experimental predictions of the model.
Exact Classical Simulation of the Quantum-Mechanical GHZ Distribution

Gilles Brassard Université de Montréal
April 16, 2014

PIRSA:14040060
Quantum Information
John Bell has shown that the correlations entailed by quantum mechanics cannot be reproduced by a classical process involving non-communicating parties. But can they be simulated with the help of bounded communication? This problem has been studied for more than twenty years and it is now well understood in the case of bipartite entanglement. However, the issue was still widely open for multipartite entanglement, even for the simplest case, which is the tripartite Greenberger-Horne-Zeilinger (GHZ) state. We give an exact simulation of arbitrary independent von Neumann measurements on general n-partite GHZ states. Our protocol requires O(n^2) bits of expected communication between the parties, and O(n log n) expected time is sufficient to carry it out in parallel. Furthermore, we need only an expectation of O(n) independent unbiased random bits, with no need for the generation of continuous real random variables nor prior shared random variables. In the case of equatorial measurements, we improve earlier results with a protocol that needs only O(n log n) bits of communication and O(log^2 n) parallel time. At the cost of a slight increase in the number of bits communicated, these tasks can be accomplished with a constant expected number of rounds.
The computational power of quantum walk

Andrew Childs University of Waterloo

April 11, 2014

PIRSA:14040135

Quantum computers have the potential to solve certain problems dramatically faster than classical computers. One of the main quantum algorithmic tools is the notion of quantum walk, a quantum mechanical analog of random walk. I will describe quantum algorithms based on this idea, including an optimal algorithm for evaluating Boolean formulas and one of the best known algorithms for simulating quantum dynamics. I will also show how quantum walk can be viewed as a universal model of quantum computation.
Almost quantum correlations

Antonio Acin Institute of Photonic Sciences (ICFO)

April 09, 2014

PIRSA:14040065

Quantum theory is successfully tested in any experimental lab every day. Apart from its experimental validity, quantum theory also constitutes a robust theoretical framework: small variations of its formalism often lead to highly implausible consequences, such as violation of the no-signalling principle or a significant increase of the computational power. In fact, it has been argued that quantum theory may represent an island in theory space. We show that, at the level of correlations, quantum theory may not be as special as initially thought. In order to do so, we define the set of almost quantum correlations and prove that this set is (i) strictly larger than the set of quantum correlations but (ii) satisfies most of the information principles introduced to characterize quantum correlations, such as local orthogonality, macroscopic locality, no advantage for nonlocal computation or non-trivial communication complexity. We also provide numerical evidence that the set is compatible with information causality. Finally, we briefly discuss how the set of almost quantum correlations naturally emerges in the consistent histories approach to quantum physics.
Scribble, Scribble

Isabella Stefanescu

April 02, 2014

PIRSA:14040117

The live performance of a drawing contains information, expression and meaning that a finished drawing does not. Part performance, part demonstration, Isabella Stefanescu’s talk will explore the artistic challenges in creating performance pieces with the Euphonopen, an assemblage of hardware and software designed to map the characteristic mark making gestures of an artist to sound. Various stages of the Euphonopen project have been presented at SIGGRAPH (2010), Concordia University Live Electroacoustic Colloquium (2011), McGill University Time Forms Conference (2013).
Effective field theory for hydrodynamical systems

Alberto Nicolis Columbia University
March 28, 2014

PIRSA:14030121
Quantum Fields and Strings

Cosmology
I will review a recently proposed formalism that describes fluids and superfluids in effective field theory terms. I will then focus on applying this formalism to peculiar string-like objects that exist in fluid systems: vortex lines and vortex rings. These do not obey Newton's second law, and, as a consequence, their behavior is highly counterintuitive. I will describe how effective field theory provides us with an optimal tool to understand how they move and how they interact with one another and with sound.
The invasion of physics by information theory

Robert Spekkens Perimeter Institute for Theoretical Physics
March 26, 2014

PIRSA:14030085
Quantum Foundations
When we think of a revolution in physics, we usually think of a physical theory that manages to overthrow its predecessor. There is another kind of revolution, however, that typically happens more slowly but that is often the key to achieving the first sort: it is the discovery of a novel perspective on an existing physical theory. The use of least-action principles, symmetry principles, and thermodynamic principles are good historical examples. It turns out that we can refine our understanding of many of these principles by characterizing certain properties of physical states as resources. I will discuss some of the highlights of two resource theories: the resource theory of asymmetry, which characterizes the relations among quantum states that break a symmetry; and the resource theory of athermality, which characterizes the relations among quantum states that deviate from thermal equilibrium. In particular, I will discuss how Noether's theorem does not capture all of the consequences of symmetries of the dynamics, and how the second law of thermodynamics does not capture all of the constraints on thermodynamic transitions. Finally, I will show that both asymmetry and athermality are informational resources, and that rehabilitated versions of Noether's theorem and the second law can both be understood as constraints on data processing. Considerations such as these---as well as evidence from other fronts of the invasion---make a compelling case for the revolutionary cause of reconceiving physics from an information-theoretic perspective.
Exact results in supersymmetric gauge theories in various dimensions

Sara Pasquetti University of Milan
March 19, 2014

PIRSA:14030084
Particle Physics
One of the central challenges in theoretical physics is to develop non-perturbative methods to describe quantitatively the dynamics of strongly coupled quantum fields. Much progress in this direction has been made for theories with a higher degree of symmetry, such as conformal symmetry or supersymmetry. In recent years the method of localisation has allowed to obtain a great deal of exact results for supersymmetric gauge theories in various dimensions which has led to the discovery of new surprising correspondences such as the celebrated Alday-Gaiotto-Tachikawa correspondence. I will review some recent results which indicate that partition functions of supersymmetric theories formulated on compact manifolds can be expressed in terms of a small set of fundamental building blocks.
Black Holes- the Harmonic Oscillators of the 21st Century

Andrew Strominger Harvard University
March 12, 2014

PIRSA:14030104
Quantum Fields and Strings
In the twentieth century, many problems across all of physics were solved by perturbative methods which reduced them to harmonic oscillators. Black holes are poised to play a similar role for the problems of twenty-first century physics. They are at once the simplest and most complex objects in the physical universe. They are maximally complex in that the number of possible microstates, or entropy, of a black hole is believed to saturate a universal bound. They are maximally simple in that, according to Einstein's theory, they are featureless holes in space characterized only by their mass, charge and angular momentum. This dual relation between simplicity and complexity, as expressed in black holes, has recently been successfully applied to problems in a disparate variety of physical systems. I will give an introduction to the subject intended for a general audience.
The Unreasonable Effectiveness Of Quantum Physics in Modern Mathematics

Robbert Dijkgraaf Institute for Advanced Study (IAS)
March 05, 2014

PIRSA:14030083
Mathematical physics
Mathematics has proven to be "unreasonably effective" in understanding nature. The fundamental laws of physics can be captured in beautiful formulae. In this lecture I want to argue for the reverse effect: Nature is an important source of inspiration for mathematics, even of the purest kind. In recent years ideas from quantum field theory, elementary particles physics and string theory have completely transformed mathematics, leading to solutions of deep problems, suggesting new invariants in geometry and topology, and, perhaps most importantly, putting modern mathematical ideas in a `natural’ context.
À la recherche du temps perdu - Templeton Frontiers Colloquia

Flavio Mercati University of Naples Federico II
February 26, 2014

PIRSA:14020100
Quantum Gravity
Augustine of Hippo declared he knew what time is until someone asked him. After 16 centuries we still largely ignore the true essence of time, but we made definite progress in studying its properties. The most striking, and somewhat intuitively (and tragically) obvious one is the irreversibility of its flow. And yet, our fundamental theories are time-reversal invariant, they do not distinguish between past and future. This is usually accounted for by assuming an immensely special initial condition of the Universe, dressed with statistical arguments. In this talk, I will show how an irreversible behaviour, and with it a growth of complexity and information, can emerge from time-reversal invariant laws, without assuming any special initial condition and without thermodynamical arguments. This phenomenon is present in General Relativity, our most advanced theory of the Universe. This irreversibility will also allow me to propose a solution of another puzzle associated with time, namely the incompatibility between the quantum and the general-relativistic notions of time.

Title	Speaker(s)	Date	Talk Type	Info
Quantum thermalization and many-body Anderson localization	David Huse	2014-04-30	Scientific Series	View details
Conformal Standard Model	Krzysztof Meissner	2014-04-23	Scientific Series	View details
Exact Classical Simulation of the Quantum-Mechanical GHZ Distribution	Gilles Brassard	2014-04-16	Scientific Series	View details
The computational power of quantum walk	Andrew Childs	2014-04-11	Scientific Series	View details
Almost quantum correlations	Antonio Acin	2014-04-09	Scientific Series	View details
Scribble, Scribble	Isabella Stefanescu	2014-04-02	Scientific Series	View details
Effective field theory for hydrodynamical systems	Alberto Nicolis	2014-03-28	Scientific Series	View details
The invasion of physics by information theory	Robert Spekkens	2014-03-26	Scientific Series	View details
Exact results in supersymmetric gauge theories in various dimensions	Sara Pasquetti	2014-03-19	Scientific Series	View details
Black Holes- the Harmonic Oscillators of the 21st Century	Andrew Strominger	2014-03-12	Scientific Series	View details
The Unreasonable Effectiveness Of Quantum Physics in Modern Mathematics	Robbert Dijkgraaf	2014-03-05	Scientific Series	View details
À la recherche du temps perdu - Templeton Frontiers Colloquia	Flavio Mercati	2014-02-26	Scientific Series	View details

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