Scientific Series

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Quantum Computing with Noninteracting Particles

Alex Arkhipov Massachusetts Institute of Technology (MIT)
April 02, 2014

PIRSA:14040077
Quantum Physics
Scribble, Scribble

Isabella Stefanescu

April 02, 2014

PIRSA:14040117
Incompatibility of observables in quantum theory and other probabilistic theories
April 01, 2014

PIRSA:14040075
Quantum Physics
Fibonacci Anyons From Abelian Bilayer Quantum Hall States

Abolhassan Vaezi Cornell University
April 01, 2014

PIRSA:14040120
Condensed Matter
RG flows with N=1 supersymmetry

Henriette Elvang University of Michigan–Ann Arbor
April 01, 2014

PIRSA:14030074
High Energy Physics
The not-so-homogeneous universe

Phil Bull Queen Mary University of London
April 01, 2014

PIRSA:14040129
Astrophysics
Effective field theory for hydrodynamical systems

Alberto Nicolis Columbia University
March 28, 2014

PIRSA:14030121
High Energy Physics

Astrophysics
Possible Astrophysical Observables of Quantum Gravity Effects near Black Holes

Ue-Li Pen Canadian Institute for Theoretical Astrophysics (CITA)
March 27, 2014

PIRSA:14030115
General Relativity & Quantum Cosmology
Bungee jumping of black holes in AdS universe
March 27, 2014

PIRSA:14030108
General Relativity & Quantum Cosmology
The invasion of physics by information theory

Robert Spekkens Perimeter Institute for Theoretical Physics
March 26, 2014

PIRSA:14030085
Quantum Physics
GeV Gamma-Rays from the Central Milky Way and the Case for Annihilating Dark Matter

Tracy Slatyer Massachusetts Institute of Technology (MIT) - Department of Physics
March 26, 2014

PIRSA:14030120
High Energy Physics
Far from equilibrium energy flow in quantum critical systems
March 25, 2014

PIRSA:14030089
High Energy Physics

Quantum Computing with Noninteracting Particles

Alex Arkhipov Massachusetts Institute of Technology (MIT)
April 02, 2014

PIRSA:14040077
Quantum Physics
We introduce an abstract model of computation corresponding to an experiment in which identical, non-interacting bosons are sent through a non-adaptive linear circuit before being measured. We show that despite the very limited nature of the model, an exact classical simulation would imply a collapse of the polynomial hierarchy. Moreover, under plausible conjectures, a "noisy" approximate simulation would do the same. This gives evidence that quantum computers can sample a distribution that classical computers cannot even approximate, even when restricted to use no entanglement except that arising from particles being identical. We briefly discuss experimental prospects for realizing this model. This talk is based on The Computational Complexity of Linear Optics [STOC '11], which is joint work with Scott Aaronson.
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).
Incompatibility of observables in quantum theory and other probabilistic theories
April 01, 2014

PIRSA:14040075
Quantum Physics
We introduce a new way of quantifying the degrees of incompatibility of two observables in a probabilistic physical theory and, based on this, a global measure of the degree of incompatibility inherent in such theories. This opens up a flexible way of comparing probabilistic theories with respect to the nonclassical feature of incompatibility. We show that quantum theory contains observables that are as incompatible as any probabilistic physical theory can have. In particular, we prove that two of the most common pairs of complementary observables (position and momentum; number and phase) are maximally incompatible. However, if one adopts a more refined measure of the degree of incompatibility, for instance, by restricting the comparison to binary observables, it turns out that there are probabilistic theories whose inherent degree of incompatibility is greater than that of quantum theory. Finally, we analyze the noise tolerance of the incompatibility of a pair of observables in a CHSH-Bell experiment.
Fibonacci Anyons From Abelian Bilayer Quantum Hall States

Abolhassan Vaezi Cornell University
April 01, 2014

PIRSA:14040120
Condensed Matter
The possibility of realizing non-Abelian statistics and utilizing it for topological quantum computation (TQC) has generated widespread interest. However, the non-Abelian statistics that can be realized in most accessible proposals is not powerful enough for universal TQC. In this talk, I consider a simple bilayer fractional quantum Hall (FQH) system with the 1/3 Laughlin state in each layer, in the presence of interlayer tunneling. I show that interlayer tunneling can drive a continuous phase transition to an exotic non-Abelian state that contains the famous `Fibonacci' anyon, whose non-Abelian statistics is powerful enough for universal TQC. The analysis that I will present towards this result rests on startling agreements from a variety of distinct methods, including thin torus limits, effective field theories, and coupled wire constructions.

Next, I discuss the experimental aspects of our proposal and potential probes for the Fibonacci phase. I show that the charge gap remains open at the phase transition while the neutral gap closes. This raises the question of whether these exotic phases may have already been realized at nu=2/3 in bilayers, as past experiments may not have definitively ruled them out. Finally, I will discuss about the generalizations to multi-layer states as well as the duality between the interlayer pairing and interlayer tunneling problems.

Reference: arXiv:1403.3383
RG flows with N=1 supersymmetry

Henriette Elvang University of Michigan–Ann Arbor
April 01, 2014

PIRSA:14030074
High Energy Physics
The dilaton effective action plays a key role for the recent proof of the a-theorem by Schwimmer and Komargodski. In the presence of other massless modes, one may ask if this proof is affected. In particular, in renormalization group (RG) flows with N=1 supersymmetry, there is a natural massless partner of the dilaton, namely an axion field. I will discuss RG flows, the a-theorem, and the form of the N=1 supersymmetric dilaton-axion effective action and its physics.
The not-so-homogeneous universe

Phil Bull Queen Mary University of London
April 01, 2014

PIRSA:14040129
Astrophysics
The assumption of spatial homogeneity lies at the heart of the concordance cosmological model. But as I will discuss, truly solid empirical evidence for global (statistical) homogeneity is lacking, and tricky theoretical issues abound. I review a few recent advances in understanding the role inhomogeneity plays in cosmology, including some unexpected effects on light propagation, the death (and rebirth) of backreaction, and impending observational annoyances related to the lumpy local Universe. I'll also talk about some near-future observations that can give us a handle on these effects
Effective field theory for hydrodynamical systems

Alberto Nicolis Columbia University
March 28, 2014

PIRSA:14030121
High Energy Physics

Astrophysics
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.
Possible Astrophysical Observables of Quantum Gravity Effects near Black Holes

Ue-Li Pen Canadian Institute for Theoretical Astrophysics (CITA)
March 27, 2014

PIRSA:14030115
General Relativity & Quantum Cosmology
Recent implications of results from quantum information theory applied to black holes has led to the confusing conclusions that requires either abandoning the equivalence principle (e.g. the firewall picture), or the no-hair theorem (e.g. the fuzzball picture), or even more unpalatable options. The recent discovery of a pulsar orbiting a black hole opens up new possibilities for tests of theories of gravity. We examine possible observational effects of semiclassical quantum gravity in the vicinity of black holes, as probed by pulsars and event horizon telescope imaging of flares. Pulsar radiation is observable at wavelengths only two orders of magnitude shorter than the Hawking radiation, so precision interferometry of lensed pulsar images may shed light on the quantum gravitational processes and interaction of Hawking radiation with the spacetime near the black hole. This paper discusses the impact on the pulsar radiation interference pattern, which is observable through the modulation index in the foreseeable future, and discusses a possible classical limit of BHC.
Bungee jumping of black holes in AdS universe
March 27, 2014

PIRSA:14030108
General Relativity & Quantum Cosmology
C-metric describes uniformly accelerated black holes. We will review a global structure of these solutions especially in Lambda<0 context. It turns out that for an acceleration larger than the cosmological one the metric describes pairs of black holes "bungee jumping" into spacetime from AdS infinity.
The invasion of physics by information theory

Robert Spekkens Perimeter Institute for Theoretical Physics
March 26, 2014

PIRSA:14030085
Quantum Physics
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.
GeV Gamma-Rays from the Central Milky Way and the Case for Annihilating Dark Matter

Tracy Slatyer Massachusetts Institute of Technology (MIT) - Department of Physics
March 26, 2014

PIRSA:14030120
High Energy Physics
Past studies have identified a spatially extended excess of ~1-3 GeV gamma rays from the Galactic Center and inner Galaxy, consistent with the emission expected from annihilating thermal relic dark matter. I will describe recent improvements in the characterization of this signal, which demonstrate that it is spherically symmetric, centered on the Galactic Center, and with a spatial profile consistent with annihilation from a cusped NFW profile. The excess can be detected out to 10 degrees from the Galactic Center, which poses challenges for a millisecond pulsar origin; I will discuss the implications of a dark matter interpretation.
Far from equilibrium energy flow in quantum critical systems
March 25, 2014

PIRSA:14030089
High Energy Physics
We investigate far from equilibrium energy transport in strongly coupled quantum critical systems. Combining results from gauge-gravity duality, relativistic hydrodynamics, and quantum field theory, we argue that long-time energy transport after a local thermal quench occurs via a universal steady-state for any spatial dimensionality. This is described by a boosted thermal state. We determine the transport properties of this emergent steady state, including the average energy flow and its long-time fluctuations.

Title	Speaker(s)	Date	Talk Type	Info link
Quantum Computing with Noninteracting Particles	Alex Arkhipov	2014-04-02	Scientific Series	View details
Scribble, Scribble	Isabella Stefanescu	2014-04-02	Scientific Series	View details
Incompatibility of observables in quantum theory and other probabilistic theories		2014-04-01	Scientific Series	View details
Fibonacci Anyons From Abelian Bilayer Quantum Hall States	Abolhassan Vaezi	2014-04-01	Scientific Series	View details
RG flows with N=1 supersymmetry	Henriette Elvang	2014-04-01	Scientific Series	View details
The not-so-homogeneous universe	Phil Bull	2014-04-01	Scientific Series	View details
Effective field theory for hydrodynamical systems	Alberto Nicolis	2014-03-28	Scientific Series	View details
Possible Astrophysical Observables of Quantum Gravity Effects near Black Holes	Ue-Li Pen	2014-03-27	Scientific Series	View details
Bungee jumping of black holes in AdS universe		2014-03-27	Scientific Series	View details
The invasion of physics by information theory	Robert Spekkens	2014-03-26	Scientific Series	View details
GeV Gamma-Rays from the Central Milky Way and the Case for Annihilating Dark Matter	Tracy Slatyer	2014-03-26	Scientific Series	View details
Far from equilibrium energy flow in quantum critical systems		2014-03-25	Scientific Series	View details

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Quantum Computing with Noninteracting Particles

Scribble, Scribble

Incompatibility of observables in quantum theory and other probabilistic theories

Fibonacci Anyons From Abelian Bilayer Quantum Hall States

RG flows with N=1 supersymmetry

The not-so-homogeneous universe

Effective field theory for hydrodynamical systems

Possible Astrophysical Observables of Quantum Gravity Effects near Black Holes

Bungee jumping of black holes in AdS universe

The invasion of physics by information theory

GeV Gamma-Rays from the Central Milky Way and the Case for Annihilating Dark Matter

Far from equilibrium energy flow in quantum critical systems

Quantum Computing with Noninteracting Particles

Scribble, Scribble

Incompatibility of observables in quantum theory and other probabilistic theories

Fibonacci Anyons From Abelian Bilayer Quantum Hall States

RG flows with N=1 supersymmetry

The not-so-homogeneous universe

Effective field theory for hydrodynamical systems

Possible Astrophysical Observables of Quantum Gravity Effects near Black Holes

Bungee jumping of black holes in AdS universe

The invasion of physics by information theory

GeV Gamma-Rays from the Central Milky Way and the Case for Annihilating Dark Matter

Far from equilibrium energy flow in quantum critical systems