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# Video Library

Since 2002 Perimeter Institute has been recording seminars, conference talks, and public outreach events using video cameras installed in our lecture theatres.  Perimeter now has 7 formal presentation spaces for its many scientific conferences, seminars, workshops and educational outreach activities, all with advanced audio-visual technical capabilities.  Recordings of events in these areas are all available On-Demand from this Video Library and on Perimeter Institute Recorded Seminar Archive (PIRSA)PIRSA is a permanent, free, searchable, and citable archive of recorded seminars from relevant bodies in physics. This resource has been partially modelled after Cornell University's arXiv.org.

## Quasi-Topological Quantum Error Correction Codes

Wednesday May 31, 2017
Speaker(s):

Existing proposals for topological quantum computation have encountered

difficulties in recent years in the form of several obstructing'' results.

These are not actually no-go theorems but they do present some serious

obstacles. A further aggravation is the fact that the known topological

error correction codes only really work well in spatial dimensions higher

than three. In this talk I will present a method for modifying a higher

## Donaldson-Thomas transformations for moduli spaces of local systems on surfaces

Wednesday May 31, 2017
Speaker(s):

Kontsevich and Soibelman defined Donaldson-Thomas invariants of a 3d Calabi-Yau category with a stability condition. Any cluster variety gives rise to a family of such categories. Their DT invariants are encapsulated in single formal automorphism of the cluster variety, called the DT-transformation. An oriented surface S with punctures, and a finite number of special points on the boundary give rise to a moduli space, closely related to the moduli space of PGL(m)-local systems on S, which carries a canonical cluster Poisson variety structure.

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## Topological Boundary Modes from Quantum Electronics to Classical Mechanics

Wednesday May 31, 2017
Speaker(s):

Over the past several years, our understanding of topological electronic phases of matter has advanced dramatically.   A paradigm that has emerged is that insulating electronic states with an energy gap fall into distinct topological classes.   Interfaces between different topological phases exhibit gapless conducting states that are protected topologically and are impossible to get rid of.   In this talk we will discuss the application of this idea to the quantum Hall effect, topological insulators,  topological superconductors and the quest for Majorana fermions in c

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## Using quantum computing techniques to detect dark matter axions

Tuesday May 30, 2017
Speaker(s):

Quantum non-demolition measurements performed using qubit-based artificial atoms may enable the next generation of higher mass dark matter axion search experiments.  These QND measurements can precisely determine the amplitude of the photon wave sourced by the dark matter axions while placing the back reaction noise into the phase quadrature.

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## The Alleged Small-Scale Problems of LambdaCDM

Tuesday May 30, 2017

The Lambda Cold Dark Matter framework successfully accounts for observational constraints on large (> 1 Mpc) scales, from the clustering of galaxies to the angular dependence of the Cosmic Microwave Background to the structure and matter content of galaxy clusters. On the scale of individual galaxies and, in particular, of dwarf systems much fainter than the Milky Way, a number of apparent conflicts with LCDM expectations have been reported.

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Thursday May 25, 2017
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## Ba3Yb2Zn5O11: A model system for anisotropic exchange on the breathing pyrochlore lattice

Thursday May 25, 2017
Speaker(s):

In this talk we present a study of the “breathing” pyrochlore compound Ba3Yb2Zn5O11. Due to the nearly decoupled nature of its tetrahedral units, this compound serves as an ideal testbed for exploring the nature of anisotropic exchange in a theoretically and experimentally tractable rare-earth system. The relevant low-energy model of the Yb3+ tetrahedra is parametrized by four anisotropic exchange constants and is capable of reproducing the inelastic neutron scattering data, specific heat, and magnetic susceptibility with high fidelity.

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## Experimental evidence for field induced emergent clock anisotropies in the XY pyrochlore Er2Ti2O7

Thursday May 25, 2017
Speaker(s):

The XY pyrochlore Er2Ti2O7 has garnered much attention due to the possibility that its ground state selection could originate from an order-by-disorder mechanism [1,2]. However, recently, theoretical work has exploited the fact that the symmetry breaking in this system is a rare case of high discrete symmetry (Z6) [3]. This work studied the effect of a magnetic field on the Z6 symmetry breaking and predicted rich and controllable magnetothermodynamic properties.

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## Understanding the Emergence of Chiral Spin Liquids in Mott Insulators

Thursday May 25, 2017
Speaker(s):

In recent years, there has been a resurgence of interest in the study of chiral spin liquids (CSLs), topologically ordered states of matter that are closely related to the celebrated fractional quantum Hall states. This resurgence has been driven by the introduction of exact parent Hamiltonians and a number of numerical studies that have identified CSLs in local spin models. However, our understanding of how and why these states emerge is still lacking.

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## Many-body physics in a trapped ion quantum simulator

Thursday May 25, 2017
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Many-body quantum systems are often hard to simulate on a computer, due to the computational complexity generated by non-classical correlations or entanglement between parts of these systems. An alternate platform is to experimentally simulate non-trivial quantum models on synthetic quantum matter composed of cold atomic systems. These systems exhibit excellent quantum coherence properties due to their isolation from environment, and hence faithfully evolve in time under the prescribed quantum Hamiltonian.

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## Next Public Lecture

Check back for details on the next lecture in Perimeter's Public Lectures Series