Conference

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Protected edge modes without symmetry

Michael Levin University of Chicago
May 06, 2013

PIRSA:13050026
Quantum Fields and Strings
Emergent Fermionic Strings in Bosonic He4 Crystal

Baskaran Ganapathy Institute of Mathematical Sciences
May 06, 2013

PIRSA:13050025
Condensed Matter
Topological Order with a Twist: Ising Anyons from an Abelian Model

Hector Bombin PsiQuantum Corp.
May 06, 2013

PIRSA:13050024
Quantum Information
Quantum spin liquid phases in the absence of spin-rotation symmetry

Yong-Baek Kim University of Toronto
May 06, 2013

PIRSA:13050023
Condensed Matter
TQFTs and Topological Phases of Matter

Zhenghan Wang Microsoft Corporation
May 06, 2013

PIRSA:13050022
Mathematical physics
3d boson topological insulators and quantum spin liquids

Senthil Todadri Massachusetts Institute of Technology (MIT) - Department of Physics
May 06, 2013

PIRSA:13050021
Condensed Matter
Diluted Magnetism in Iridates: Studies of Rh-doped Sr2Ir2O4

Pat Clancy University of Toronto
April 25, 2013

PIRSA:13040137
Condensed Matter
Higgs Boson in Condensed Matter: From Polaron to Topological Insulator
April 25, 2013

PIRSA:13040132
Particle Physics

Condensed Matter
Tensor Networks: an Overview

Lukasz Cincio Los Alamos National Laboratory
April 25, 2013

PIRSA:13040131
Quantum Information
New Neutron Scattering Results on the Enigmatic Ground State of the Pyrochlore Magnet Tb2Ti2O7

Katharina Fristsch McMaster University
April 25, 2013

PIRSA:13040136
Condensed Matter
Absence of Pauling's Residual Entropy in Dy2Ti2O

Jan Kycia University of Waterloo
April 25, 2013

PIRSA:13040130
Condensed Matter
The Quantum von Neumann Architecture and the Future of Quantum Computing with Superconducting Circuits

Matteo Mariantoni Institute for Quantum Computing (IQC)

April 25, 2013

PIRSA:13040135

Protected edge modes without symmetry

Michael Levin University of Chicago
May 06, 2013

PIRSA:13050026
Quantum Fields and Strings
Some 2D quantum many-body systems with a bulk energy gap support gapless edge modes which are extremely robust. These modes cannot be gapped out or localized by general classes of interactions or disorder at the edge: they are "protected" by the structure of the bulk phase. Examples of this phenomena include quantum Hall states and 2D topological insulators, among others. Recently, much progress has been made in understanding protected edge modes in non-interacting fermion systems. However, less is known about the interacting case. A basic problem is to predict, for general interacting systems, when such edge modes are present or absent, and to identify the different physical mechanisms that underlie their stability. In this talk, I will discuss this problem in the simplest case: interacting fermion systems without any symmetry.
Emergent Fermionic Strings in Bosonic He4 Crystal

Baskaran Ganapathy Institute of Mathematical Sciences
May 06, 2013

PIRSA:13050025
Condensed Matter
Large zero point motion of light atoms in solid Helium 4 leads to several anomalous properties, including a supersolid type behavior. We suggest an `anisotropic quantum melted' atom density wave model for solid He4 with hcp symmetry. Here, atoms preferentially quantum melt along the c-axis and maintain self organized crystallinity and confined dynamics along ab-plane. This leads to profound consequences: i) statistics transmutation of He4 atoms into fermions for c-axis dynamics, arising from restricted one dimensional motion and hard core repulsion, ii) resulting `fermionic strings' undergo Peierls instability (an atom density wave formation) in a staggered fashion and help regain the original hcp crystal symmetry, iii) `particle-hole' type excitations iv) emergence of `confined' `half atom' domain wall excitations, and so on. Known anomalies of solid He4 gets a natural qualitative explanation in the present scenario.
Topological Order with a Twist: Ising Anyons from an Abelian Model

Hector Bombin PsiQuantum Corp.
May 06, 2013

PIRSA:13050024
Quantum Information
Anyon models can be symmetric under some permutations of their topological charges. One can then conceive topological defects that, under monodromy, transform anyons according to a symmetry. We study the realization of such defects in the toric code model, showing that a process where defects are braided and fused has the same outcome as if they were Ising anyons.
Quantum spin liquid phases in the absence of spin-rotation symmetry

Yong-Baek Kim University of Toronto
May 06, 2013

PIRSA:13050023
Condensed Matter
We investigate possible quantum spin liquid phases in the presence of a variety of spin-rotational-symmetry breaking perturbations. Projective symmetry group analysis on slave-particle representations is used to understand possible spin liquid phases on the Kagome lattice. The results of this analysis are used to make connections to the exiting and future experiments on Herbertsmithites. Applications to other systems are also discussed.
TQFTs and Topological Phases of Matter

Zhenghan Wang Microsoft Corporation
May 06, 2013

PIRSA:13050022
Mathematical physics
In two spatial dimensions, there is a good correspondence between TQFTs and topological phases of matter for spin systems. I will discuss this correspondence in one and three spatial dimensions for spin systems. If time permits, I will also discuss the situation for fermion systems.
3d boson topological insulators and quantum spin liquids

Senthil Todadri Massachusetts Institute of Technology (MIT) - Department of Physics
May 06, 2013

PIRSA:13050021
Condensed Matter
I will discuss recent work on 3d Symmetry Protected Topological (SPT) phases of bosonic systems, and their implications for understanding the more exotic quantum spin liquid phases. First I will describe various characterizations of these 3d SPT phases, in particular their surface effective theories and (when applicable) bulk electromagnetic response. Next I will show how this understanding leads to several new insights into the theory of both 2d and 3d quantum spin liquids. Finally I will provide an explicit construction of several 3d SPT phases in a system of `coupled layers'. This includes a 3d SPT state that is beyond the existing cohomology classification of such states.
Diluted Magnetism in Iridates: Studies of Rh-doped Sr2Ir2O4

Pat Clancy University of Toronto
April 25, 2013

PIRSA:13040137
Condensed Matter
The physics of iridium-based 5d transition metal oxides has attracted significant interest due to the potential for exotic magnetic and electronic ground states driven by strong spin-orbit coupling effects. Among the most extensively studied iridates is the layered perovskite Sr2IrO4, which was recently proposed as the first experimental realization of a novel Jeff=1/2 spin-orbital Mott insulating state. Intriguing similarities between Sr2IrO4 and La2CuO4, the parent compound of the high-Tc cuprates, have also led to speculation that it may be possible to induce superconductivity in this system through chemical doping. We have investigated the magnetic properties of the doped system Sr2Ir1-xRhxO4 using a combination of resonant magnetic x-ray scattering (RMXS), resonant inelastic x-ray scattering (RIXS), and x-ray absorption spectroscopy (XAS) techniques. These measurements reveal the effect of Rh-doping on the magnetic structure, phase diagram, and characteristic magnetic excitations of Sr2IrO4, and provide fundamental information about the role of quenched Rh impurities.
Higgs Boson in Condensed Matter: From Polaron to Topological Insulator
April 25, 2013

PIRSA:13040132
Particle Physics

Condensed Matter
In this talk I will briefly review the polaron physics, which has helped theorists to conceive the BCS theory of conventional superconductors as well as experimentalists to discover high temperature superconductors in the cuprates. Specifically I will talk about how charge carriers obtain their
masses from coupling to the phonon field in one, two, three or higher dimensions. More recently, there is increasing interest in topological insulators where a gap can be opened which may suggest new version of Higgs mechanism in condensed matter.
Tensor Networks: an Overview

Lukasz Cincio Los Alamos National Laboratory
April 25, 2013

PIRSA:13040131
Quantum Information
Tensor network algorithms provide highly competitive tools for analyzing ground state properties of quantum lattice models in one and two spatial dimensions. The most notable examples involve matrix product states, projected entangled pair states and multiscale entanglement renormalization ansatz. The key underlying idea of all the approaches is to decompose a quantum many-body state into a carefully chosen network of tensors.
In this talk I will give an introduction to the subject and show how tensor networks can be used to characterize topological order.
New Neutron Scattering Results on the Enigmatic Ground State of the Pyrochlore Magnet Tb2Ti2O7

Katharina Fristsch McMaster University
April 25, 2013

PIRSA:13040136
Condensed Matter
The ground state of the candidate spin liquid pyrochlore magnet Tb2Ti2O7 (TTO) has been long debated. Despite theoretical expectations of magnetic order below ~1K based on classical Ising-like Tb3+ spins, earlier muSR and neutron scattering experiments showed no long range order down to 50mK. This motivated two theoretical scenarios to account for the apparently disordered ground state: a quantum spin ice scenario and a non-magnetic singlet ground state. I will discuss new neutron scattering measurements on TTO that show short range spin correlations developing below ~ 0.5 K with a (½, ½, ½) ordering wavevector, and a concomitant opening of a spin gap across most of the Brillouin zone. Our measurements also refine the crystal field ground state for Tb3+ in TTO and in its sister, “soft” spin ice compound Tb2Sn2O7.
Absence of Pauling's Residual Entropy in Dy2Ti2O

Jan Kycia University of Waterloo
April 25, 2013

PIRSA:13040130
Condensed Matter
The discovery of the spin-ice phase in Dy2Ti2O7 numbers among the most significant findings in magnetic materials in over a decade. The spin-ice model is based on an elegant analogy to Pauling’s model of geometrical frustration in water ice, and predicts the same residual entropy, as confirmed by numerous measurements. Melko, den Hertog and Gingras, with numerical work using a loop algorithm to speed up equilibration times, were able to determine an ordering for this system. This had not been seen experimentally observed by several groups. I will present new experimental results for the specific heat of Dy2Ti2O7, demonstrating why previous measurements were unable to correctly capture its low temperature behaviour. By carefully tracking the flow of heat into and out of the material, we observe a non-vanishing specific heat at low temperatures indicating the residual entropy does not actually agree with the Pauling value.
The Quantum von Neumann Architecture and the Future of Quantum Computing with Superconducting Circuits

Matteo Mariantoni Institute for Quantum Computing (IQC)

April 25, 2013

PIRSA:13040135

Superconducting quantum circuits have made significant advances over the past decade, allowing more complex and integrated circuits that perform with good fidelity. We have recently implemented a machine comprising seven quantum channels, with three superconducting resonators, two phase qubits, and two zeroing registers. I will explain the design and operation of this machine, first showing how a single microwave photon |1> can be prepared in one resonator and coherently transferred between the three resonators [1]. I will then demonstrate how this machine can be used as the quantum-mechanical analog of the von Neumann computer architecture, which for a classical computer comprises a central processing unit and a memory holding both instructions and data. The quantum version comprises a quantum central processing unit (quCPU) that exchanges data with a quantum random-access memory (quRAM) integrated on one chip, with instructions stored on a classical computer [2]. Finally, I will demonstrate that the quantum von Neumann machine provides one unit cell of a two-dimensional qubit-resonator array that can be used for surface code quantum computing. This will allow the realization of a scalable, fault-tolerant quantum processor with the most forgiving error rates to date [3].
[1] M. Mariantoni et al., Nature Physics 7, 287-293 (2011)
[2] M. Mariantoni et al., Science 334, 61-65 (2011)
[3] A. G. Fowler, M. Mariantoni, J. M. Martinis, and A. N. Cleland, Phys. Rev. A 86, 032324 (2012)

Title	Speaker(s)	Date	Talk Type	Info link
Protected edge modes without symmetry	Michael Levin	2013-05-06	Conference	View details
Emergent Fermionic Strings in Bosonic He4 Crystal	Baskaran Ganapathy	2013-05-06	Conference	View details
Topological Order with a Twist: Ising Anyons from an Abelian Model	Hector Bombin	2013-05-06	Conference	View details
Quantum spin liquid phases in the absence of spin-rotation symmetry	Yong-Baek Kim	2013-05-06	Conference	View details
TQFTs and Topological Phases of Matter	Zhenghan Wang	2013-05-06	Conference	View details
3d boson topological insulators and quantum spin liquids	Senthil Todadri	2013-05-06	Conference	View details
Diluted Magnetism in Iridates: Studies of Rh-doped Sr2Ir2O4	Pat Clancy	2013-04-25	Conference	View details
Higgs Boson in Condensed Matter: From Polaron to Topological Insulator		2013-04-25	Conference	View details
Tensor Networks: an Overview	Lukasz Cincio	2013-04-25	Conference	View details
New Neutron Scattering Results on the Enigmatic Ground State of the Pyrochlore Magnet Tb2Ti2O7	Katharina Fristsch	2013-04-25	Conference	View details
Absence of Pauling's Residual Entropy in Dy2Ti2O	Jan Kycia	2013-04-25	Conference	View details
The Quantum von Neumann Architecture and the Future of Quantum Computing with Superconducting Circuits	Matteo Mariantoni	2013-04-25	Conference	View details

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