Scientific Series

Displaying 3169 - 3180 of 5012

Hardness of correcting errors on a stabilizer code

Pavithran Iyer
January 22, 2014

PIRSA:14010099
Quantum Information
Does the Quantum Particle know its own Energy?

Rafael Sorkin
Perimeter Institute for Theoretical Physics
January 21, 2014

PIRSA:14010106
Quantum Foundations
Boundaries and Defects in 4d N=4 SYM

Masahito Yamazaki
University of Tokyo
January 21, 2014

PIRSA:14010086
Quantum Fields and Strings
Paying the price of naturalness with a supersymmetric twin Higgs

Kiel Howe
Stanford University
January 21, 2014

PIRSA:14010105
Condensed Matter
The McV black hole and the scalar theories that support it

Michele Fontanini
January 21, 2014

PIRSA:14010082
Cosmology
Gaugino physics of split supersymmetry spectrum at the LHC and future proton colliders

Sunghoon Jung
Korea Institute for Advanced Study
January 16, 2014

PIRSA:14010103
Particle Physics
Entanglement farming: Harnessing the properties of fixed points in quantum evolution

Eduardo Martin-Martinez
Institute for Quantum Computing (IQC)
January 15, 2014

PIRSA:14010104
Quantum Information
Beyond the Standard Paradigm

Paul Langacker
Institute for Advanced Study (IAS)
January 15, 2014

PIRSA:13010116
Particle Physics
Noncontextuality without determinism and admissible (in)compatibility relations: revisiting Specker's parable.

Ravi Kunjwal
Funds for Scientific Research - FNRS
January 14, 2014

PIRSA:14010102
Quantum Foundations
Simulating the Universe(s)

Matthew Johnson
York University
January 14, 2014

PIRSA:14010101
Cosmology
The computational power of matchgates and the XY interaction on arbitrary graphs

Daniel Brod
Universidade Federal Fluminense
January 08, 2014

PIRSA:14010085
Quantum Information
Scale-free primordial cosmology

Anna Ijjas
Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
December 19, 2013

PIRSA:13120063
Cosmology

Hardness of correcting errors on a stabilizer code

Pavithran Iyer
January 22, 2014

PIRSA:14010099
Quantum Information
Problems in computer science are often classified based on the scaling of the runtimes for algorithms that can solve the problem. Easy problems are efficiently solvable but often in physics we encounter problems that take too long to be solved on a classical computer. Here we look at one such problem in the context of quantum error correction. We will further show that no efficient algorithm for this problem is likely to exist. We will address the computational hardness of a decoding problem, pertaining to quantum stabilizer codes considering independent X and Z errors on each qubit. Much like classical linear codes, errors are detected by measuring certain check operators which yield an error syndrome, and the decoding problem consists of determining the most likely recovery given the syndrome. The corresponding classical problem is known to be NP-Complete, and a similar decoding problem for quantum codes is known to be NP-Complete too. However, this decoding strategy is not optimal in the quantum setting as it does not take into account error degeneracy, which causes distinct errors to have the same effect on the code. Here, we show that optimal decoding of stabilizer codes is computationally much harder than optimal decoding of classical linear codes, it is #P-Complete.
Does the Quantum Particle know its own Energy?

Rafael Sorkin
Perimeter Institute for Theoretical Physics
January 21, 2014

PIRSA:14010106
Quantum Foundations
If a wave function does not describe microscopic reality then what does? Reformulating quantum mechanics in path-integral terms leads to a notion of ``precluded event" and thence to the proposal that quantal reality differs from classical reality in the same way as a set of worldlines differs from a single worldline. One can then ask, for example, which sets of electron trajectories correspond to a Hydrogen atom in its ground state and how they differ from those of an excited state. We address the analogous questions for simple model that replaces the electron by a particle hopping (in discrete time) on a circular lattice.
Boundaries and Defects in 4d N=4 SYM

Masahito Yamazaki
University of Tokyo
January 21, 2014

PIRSA:14010086
Quantum Fields and Strings
We discuss boundary conditions and domain walls in 4d N=4 SYM, focusing on those preserving 4 supercharges. Along the way we revisit the old problem of the quantum-corrected moduli space of 3d N=2 theories.
Paying the price of naturalness with a supersymmetric twin Higgs

Kiel Howe
Stanford University
January 21, 2014

PIRSA:14010105
Condensed Matter
What is the price of naturalness? In minimal extensions of the standard model, stringent limits on new colored particles and measurements of Higgs properties from the LHC severely challenge the hypothesis of naturalness of the electroweak scale. However, these measurements also provide unprecedented guidance in exploring non-minimal models of new electroweak physics. The supersymmetric twin Higgs provides a concrete example where few-percent level tuning remains compatible with superpartner limits and Higgs physics as well as gauge coupling unification and other successes of the MSSM. Studying such models in detail is crucial to understanding the role naturalness will play as a motivating principle for future searches at the 13 TeV LHC and beyond.
The McV black hole and the scalar theories that support it

Michele Fontanini
January 21, 2014

PIRSA:14010082
Cosmology
Systems in which the local gravitational attraction is coupled to the expansion of the Universe have been studied since the early stages of General Relativity as the pioneering works of McVittie show. In this talk I start reviewing the McVittie black hole solution and its variable mass generalization from a classical fluid approach to understand its properties. I then move to a field theoretical analysis to investigate the scalar theories that support such black holes.
Gaugino physics of split supersymmetry spectrum at the LHC and future proton colliders

Sunghoon Jung
Korea Institute for Advanced Study
January 16, 2014

PIRSA:14010103
Particle Physics
Discovery of the Higgs boson and lack of discovery of superpartners in the first run at LHC are both predictions of split supersymmetry with thermal dark matter. We discuss what it would take to find gluinos at hadron supercolliders, including the LHC at 14 TeV center of mass energy, and future pp colliders at 100 TeV and 200 TeV. We generalize the discussion by re-expressing the search capacity in terms of gluino to lightest superpartner mass ratio, and apply results to other scenarios, such as gauge mediation and mirage mediation. In those models, distinctive gaugino mass ratios arise at leading order, but can be significantly modified by large logarithmic quantum corrections from split spectrum.
Entanglement farming: Harnessing the properties of fixed points in quantum evolution

Eduardo Martin-Martinez
Institute for Quantum Computing (IQC)
January 15, 2014

PIRSA:14010104
Quantum Information
We show that in certain generic circumstances the state of light of an optical cavity traversed by beams of atoms is naturally driven towards a non-thermal metastable state. This state can be such that successive pairs of unentangled particles sent through the cavity will reliably emerge significantly entangled thus providing a renewable source of quantum entanglement. Significant for possible experimental realizations is the fact that this entangling fixed point state of the cavity can be reached largely independently of the initial state in which the cavity was prepared. Our results suggest that reliable entanglement farming on the basis of such a fixed point state should be possible also in various other experimental settings, namely with the to-be-entangled particles replaced by arbitrary qudits and with the cavity replaced by a suitable reservoir system.
Beyond the Standard Paradigm

Paul Langacker
Institute for Advanced Study (IAS)
January 15, 2014

PIRSA:13010116
Particle Physics
I reexamine the current situation in particle and neutrino physics from a top-down perspective, discussing such underlying issues as uniqueness versus environment, minimality versus remnants, and naturalness versus tuning.
Noncontextuality without determinism and admissible (in)compatibility relations: revisiting Specker's parable.

Ravi Kunjwal
Funds for Scientific Research - FNRS
January 14, 2014

PIRSA:14010102
Quantum Foundations
The purpose of this talk is twofold: First, following Spekkens, to motivate noncontextuality as a natural principle one might expect to hold in nature and introduce operational noncontextuality inequalities motivated by a contextuality scenario first considered by Ernst Specker. These inequalities do not rely on the assumption of outcome-determinism which is implicit in the usual Kochen-Specker (KS) inequalities. We argue that they are the appropriate generalization of KS inequalities, serving as a test for the possibility of noncontextual explanations of experimental data. This is very much in the spirit of Bell inequalities, which provide theory-independent tests for local hidden variable explanations of experimental data without relying on the assumption of outcome-determinism. The second purpose is to point out a curious feature of quantum theory, motivated by the connections between (in)compatibility and (non)contextuality: namely, that it admits all conceivable (in)compatibility relations between observables.
Simulating the Universe(s)

Matthew Johnson
York University
January 14, 2014

PIRSA:14010101
Cosmology
The theory of eternal inflation in an inflaton potential with multiple vacua predicts that our universe is one of many bubble universes nucleating and growing inside an ever-expanding false vacuum. The collision of our bubble with another could provide an important observational signature to test this scenario. In this talk I will describe an algorithm for accurately computing the cosmological observables arising from bubble collisions directly from the Lagrangian of a single scalar field. This represents the first fully-relativistic set of predictions from an ensemble of scalar field models giving rise to eternal inflation, and I will describe on-going phenomenological studies and observational searches.
The computational power of matchgates and the XY interaction on arbitrary graphs

Daniel Brod
Universidade Federal Fluminense
January 08, 2014

PIRSA:14010085
Quantum Information
Matchgates are a restricted set of two-qubit gates known to be classically simulable when acting on nearest-neighbor qubits on a path, but universal for quantum computation when the gates can also act on more distant qubits. In this talk, I will address the power of matchgates when they can act on pairs of qubits according to the edges of arbitrary graphs. Specifically, we show that matchgates are universal on any connected graph other than a path or a cycle, and that they are classically simulable on a cycle. We also prove that the same dichotomy holds for the XY interaction, a proper subset of matchgates that arises naturally in some implementations of quantum computing. This is based on a joint work with Ernesto Galvão and another with Andrew Childs.
Scale-free primordial cosmology

Anna Ijjas
Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
December 19, 2013

PIRSA:13120063
Cosmology
The large-scale structure of the universe suggests that the physics underlying its early evolution is scale-free. In this talk, using a hydrodynamic approach, I will discuss how the scale-free principle restores predictive power and makes it possible to evaluate inflationary models and to compare them with alternative cosmologies.

Title	Speaker(s)	Date	Talk Type	Info link
Hardness of correcting errors on a stabilizer code	Pavithran Iyer	2014-01-22	Scientific Series	View details
Does the Quantum Particle know its own Energy?	Rafael Sorkin	2014-01-21	Scientific Series	View details
Boundaries and Defects in 4d N=4 SYM	Masahito Yamazaki	2014-01-21	Scientific Series	View details
Paying the price of naturalness with a supersymmetric twin Higgs	Kiel Howe	2014-01-21	Scientific Series	View details
The McV black hole and the scalar theories that support it	Michele Fontanini	2014-01-21	Scientific Series	View details
Gaugino physics of split supersymmetry spectrum at the LHC and future proton colliders	Sunghoon Jung	2014-01-16	Scientific Series	View details
Entanglement farming: Harnessing the properties of fixed points in quantum evolution	Eduardo Martin-Martinez	2014-01-15	Scientific Series	View details
Beyond the Standard Paradigm	Paul Langacker	2014-01-15	Scientific Series	View details
Noncontextuality without determinism and admissible (in)compatibility relations: revisiting Specker's parable.	Ravi Kunjwal	2014-01-14	Scientific Series	View details
Simulating the Universe(s)	Matthew Johnson	2014-01-14	Scientific Series	View details
The computational power of matchgates and the XY interaction on arbitrary graphs	Daniel Brod	2014-01-08	Scientific Series	View details
Scale-free primordial cosmology	Anna Ijjas	2013-12-19	Scientific Series	View details

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