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Processing quantum information with relativistic motion of atoms

Eduardo Martin-Martinez University of Waterloo
May 13, 2013

PIRSA:13050017
Quantum Physics
Entanglement at strongly-interacting quantum critical points in 2+1D

Roger Melko University of Waterloo
May 10, 2013

PIRSA:13050051
Quantum Physics
A gauge theory generalization of the fermion-doubling theorem

John McGreevy University of California, San Diego
May 10, 2013

PIRSA:13050050
High Energy Physics

Condensed Matter
Momentum polarization: an entanglement measure of topological spin and chiral central charge

Xiaoliang Qi Stanford University
May 10, 2013

PIRSA:13050047
Condensed Matter
Twisted Symmetry in Tensor Network States and Topological Order

Oliver Buerschaper Multiverse Computing (Germany)
May 10, 2013

PIRSA:13050048
Quantum Physics

Condensed Matter
Defects in Topologically Ordered Quantum Matter

Maissam Barkeshli University of California, Santa Barbara
May 10, 2013

PIRSA:13050053
Condensed Matter
Geometry and the entanglement spectrum in the fractional quantum Hall effect.
May 10, 2013

PIRSA:13050049
Condensed Matter
Topological Phases with of Bosons with Short Range Quantum Entanglement

Ashvin Vishwanath Harvard University
May 10, 2013

PIRSA:13050046
Condensed Matter
Spin-orbital quantum liquid on the honeycomb lattice

Philippe Corboz Universiteit van Amsterdam
May 09, 2013

PIRSA:13050045
Quantum Physics

Condensed Matter
Characterizing topological spin liquids using PEPS

Norbert Schuch Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
May 09, 2013

PIRSA:13050044
Quantum Physics
The effective field theory of general relativity, running couplings and Asymptotic Safety

John Donoghue University of Massachusetts Amherst
May 09, 2013

PIRSA:13050003
General Relativity & Quantum Cosmology
Emergence and Entanglement in Matrix Product States

Frank Verstraete Ghent University
May 09, 2013

PIRSA:13050043
Quantum Physics

Processing quantum information with relativistic motion of atoms

Eduardo Martin-Martinez University of Waterloo
May 13, 2013

PIRSA:13050017
Quantum Physics
We show that particle detectors, such as 2-level atoms, in non-inertial motion (or in gravitational fields) could be used to build quantum gates for the processing of quantum information. Concretely, we show that through suitably chosen non-inertial trajectories of the detectors the interaction Hamiltonian's time dependence can be modulated to yield arbitrary rotations in the Bloch sphere due to relativistic quantum effects. Ref. Phys. Rev. Lett. 110, 160501 (2013)
Entanglement at strongly-interacting quantum critical points in 2+1D

Roger Melko University of Waterloo
May 10, 2013

PIRSA:13050051
Quantum Physics
In two or more spatial dimensions, leading-order contributions to the scaling of entanglement entropy typically follow the "area" or boundary law. Although this leading-order scaling is non-universal, at a quantum critical point (QCP), the sub-leading behavior does contain universal physics. Different universal functions can be access through entangling regions of different geometries. For example, for polygonal shaped regions, quantum field theories have demonstrated that the subleading scaling is logarithmic, with a universal coefficient dependent on the number of vertices in the polygon. Although such universal quantities are routinely studied in non-interacting field theories, it often requires numerical simulation to access them in interacting theories. In this talk, I discuss quantum Monte Carlo (QMC) and numerical Linked-Cluster Expansion (NLCE) calculations of the Renyi entropies at the transverse-field Ising model QCP on the 2D square lattice. We calculate the universal coefficient of the vertex-induced logarithmic scaling term, and compare to non-interacting field theory calculations by Casini and Huerta. Also, we examine the shape dependence of the Renyi entropy for finite-size toroidal lattices with smooth boundaries. Such geometries provide a sensitive probe of the gapless wave function in the thermodynamic limit, and give new universal quantities that could be examined by future field-theoretical studies in 2+1D.
A gauge theory generalization of the fermion-doubling theorem

John McGreevy University of California, San Diego
May 10, 2013

PIRSA:13050050
High Energy Physics

Condensed Matter
This talk is about obstructions to symmetry-preserving regulators of quantum field theories in 3+1 dimensions. New examples of such obstructions can be found using the fact that 4+1-dimensional SPT states are characterized by their edge states.
(Based on work in progress with S.M. Kravec.)
Momentum polarization: an entanglement measure of topological spin and chiral central charge

Xiaoliang Qi Stanford University
May 10, 2013

PIRSA:13050047
Condensed Matter
Topologically ordered states are quantum states of matter with topological ground state degeneracy and quasi-particles carrying fractional quantum numbers and fractional statistics. The topological spin is an important property of a topological quasi-particle, which is the Berry phase obtained in the adiabatic self-rotation of the quasi-particle by . For chiral topological states with robust chiral edge states, another fundamental topological property is the edge state chiral central charge . In this paper we propose a new approach to compute the topological spin and chiral central charge in lattice models by defining a new quantity named as the momentum polarization. Momentum polarization is defined on the cylinder geometry as a universal subleading term in the average value of a "partial translation operator". We show that the momentum polarization is a quantum entanglement property which can be computed from the reduced density matrix, and our analytic derivation based on edge conformal field theory shows that the momentum polarization measures the combination of topological spin and central charge. Numerical results are obtained for two example systems, the non-Abelian phase of the honeycomb lattice Kitaev model, and the Laughlin state of a fractional Chern insulator described by a variational Monte Carlo wavefunction. The numerical results verifies the analytic formula with high accuracy, and further suggests that this result remains robust even when the edge states cannot be described by a conformal field theory. Our result provides a new efficient approach to characterize and identify topological states of matter from finite size numerics.
Twisted Symmetry in Tensor Network States and Topological Order

Oliver Buerschaper Multiverse Computing (Germany)
May 10, 2013

PIRSA:13050048
Quantum Physics

Condensed Matter
Defects in Topologically Ordered Quantum Matter

Maissam Barkeshli University of California, Santa Barbara
May 10, 2013

PIRSA:13050053
Condensed Matter
I will discuss recent advances in our understanding of extrinsic defects in topologically ordered states. These include line defects, where I will discuss recent developments in the classification of gapped boundaries between Abelian topological states, and various kinds of point defects, which host a rich set of topological physics. The extrinsic point defects provide a new way of realizing topologically protected ground state degeneracies, they carry projective non-abelian statistics even in an Abelian topological state and provide a new path towards universal topological quantum computation, they host a general class of topologically protected "parafermion" zero modes, and they provide an avenue towards distinguishing various symmetry-enriched topological phases. I will discuss several novel physical realizations of such point defects, and also a recent experimental proposal to realize such defects in conventional bilayer fractional quantum Hall systems.
Geometry and the entanglement spectrum in the fractional quantum Hall effect.
May 10, 2013

PIRSA:13050049
Condensed Matter
Fractional quantum hall states with nu = p/q have a characteristic geometry defined by the electric quadrupole moment of the neutral composite boson that is formed by "flux attachment" of q "flux quanta" (guiding-center orbitals) to p charged particles. This characterizes the "Hall viscosity". For FQHE states described by a conformal field theory with a Euclidean metric g_ab, the quadrupole moment is proportional to the "guiding-center spin" of the composite boson and the inverse metric. The geometry gives rise to dipole moments at external edges or internal "orbital entanglement cuts", and can be seen in the entanglement spectrum.
Topological Phases with of Bosons with Short Range Quantum Entanglement

Ashvin Vishwanath Harvard University
May 10, 2013

PIRSA:13050046
Condensed Matter
Spin-orbital quantum liquid on the honeycomb lattice

Philippe Corboz Universiteit van Amsterdam
May 09, 2013

PIRSA:13050045
Quantum Physics

Condensed Matter
The symmetric Kugel-Khomskii can be seen as a minimal model describing the interactions between spin and orbital degrees of freedom in certain transition-metal oxides with orbital degeneracy, and it is equivalent to the SU(4) Heisenberg model of four-color fermionic atoms. We present simulation results for this model on various two-dimensional lattices obtained with infinite projected-entangled pair states (iPEPS), an efficient variational tensor-network ansatz for two dimensional wave functions in the thermodynamic limit. We find a rich variety of exotic phases: while on the square and checkerboard lattices the ground state exhibits dimer-N\'eel order and plaquette order, respectively, quantum fluctuations on the honeycomb lattice destroy any order, giving rise to a spin-orbital liquid. Our results are supported from flavor-wave theory and exact diagonalization. Furthermore, the properties of the spin-orbital liquid state on the honeycomb lattice are accurately accounted for by a projected variational wave-function based on the pi-flux state of fermions on the honeycomb lattice at 1/4-filling. In that state, correlations are algebraic because of the presence of a Dirac point at the Fermi level, suggesting that the ground state is an algebraic spin-orbital liquid. This model provides a possible starting point to understand the recently discovered spin-orbital liquid behavior of Ba_3CuSb_2O_9. The present results also suggest to choose optical lattices with honeycomb geometry in the search for quantum liquids in ultra-cold four-color fermionic atoms.
Characterizing topological spin liquids using PEPS

Norbert Schuch Max Planck Institute for Gravitational Physics - Albert Einstein Institute (AEI)
May 09, 2013

PIRSA:13050044
Quantum Physics
Projected Entangled Pair States (PEPS) provide a local description of correlated many-body states. I will discuss how PEPS can be used to characterize topological spin liquids, in particular Resonating Valence Bond states. On the one hand, I will show how the symmetries in the local PEPS description allow to identify that these states appear as topologically degenerate ground states of local Hamiltonians. On the other hand, I will discuss how from exact diagonalization of the transfer operator one can extract both the topological order and the spin liquid nature of the ground state.
The effective field theory of general relativity, running couplings and Asymptotic Safety

John Donoghue University of Massachusetts Amherst
May 09, 2013

PIRSA:13050003
General Relativity & Quantum Cosmology
Effective field theory techniques allow reliable quantum calculations in general relativity at low energy. After a review of these techniques, I will discuss the attempts to define the gravitational corrections to running gauge couplings and to the couplings of gravity itself. I will also describe an attempt to understand the relation between the effective field theory and Asymptotic Safety in the region where they overlap.
Emergence and Entanglement in Matrix Product States

Frank Verstraete Ghent University
May 09, 2013

PIRSA:13050043
Quantum Physics

Title	Date	Collection	Type	Info
Processing quantum information with relativistic motion of atoms	2013‑05‑13	Perimeter Institute Quantum Discussions	Scientific Series	View details
Entanglement at strongly-interacting quantum critical points in 2+1D	2013‑05‑10	Emergence & Entanglement II 2013	Conference	View details
A gauge theory generalization of the fermion-doubling theorem	2013‑05‑10	Emergence & Entanglement II 2013	Conference	View details
Momentum polarization: an entanglement measure of topological spin and chiral central charge	2013‑05‑10	Emergence & Entanglement II 2013	Conference	View details
Twisted Symmetry in Tensor Network States and Topological Order	2013‑05‑10	Emergence & Entanglement II 2013	Conference	View details
Defects in Topologically Ordered Quantum Matter	2013‑05‑10	Emergence & Entanglement II 2013	Conference	View details
Geometry and the entanglement spectrum in the fractional quantum Hall effect.	2013‑05‑10	Emergence & Entanglement II 2013	Conference	View details
Topological Phases with of Bosons with Short Range Quantum Entanglement	2013‑05‑10	Emergence & Entanglement II 2013	Conference	View details
Spin-orbital quantum liquid on the honeycomb lattice	2013‑05‑09	Emergence & Entanglement II 2013	Conference	View details
Characterizing topological spin liquids using PEPS	2013‑05‑09	Emergence & Entanglement II 2013	Conference	View details
The effective field theory of general relativity, running couplings and Asymptotic Safety	2013‑05‑09	Quantum Gravity	Scientific Series	View details
Emergence and Entanglement in Matrix Product States	2013‑05‑09	Emergence & Entanglement II 2013	Conference	View details

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Format results

Processing quantum information with relativistic motion of atoms

Entanglement at strongly-interacting quantum critical points in 2+1D

A gauge theory generalization of the fermion-doubling theorem

Momentum polarization: an entanglement measure of topological spin and chiral central charge

Twisted Symmetry in Tensor Network States and Topological Order

Defects in Topologically Ordered Quantum Matter

Geometry and the entanglement spectrum in the fractional quantum Hall effect.

Topological Phases with of Bosons with Short Range Quantum Entanglement

Spin-orbital quantum liquid on the honeycomb lattice

Characterizing topological spin liquids using PEPS

The effective field theory of general relativity, running couplings and Asymptotic Safety

Emergence and Entanglement in Matrix Product States

Processing quantum information with relativistic motion of atoms

Entanglement at strongly-interacting quantum critical points in 2+1D

A gauge theory generalization of the fermion-doubling theorem

Momentum polarization: an entanglement measure of topological spin and chiral central charge

Twisted Symmetry in Tensor Network States and Topological Order

Defects in Topologically Ordered Quantum Matter

Geometry and the entanglement spectrum in the fractional quantum Hall effect.

Topological Phases with of Bosons with Short Range Quantum Entanglement

Spin-orbital quantum liquid on the honeycomb lattice

Characterizing topological spin liquids using PEPS

The effective field theory of general relativity, running couplings and Asymptotic Safety

Emergence and Entanglement in Matrix Product States