Quantum Information Seminars

Quantum Double Cluster States

Speaker: 
Courtney Brell
Event Date and Time: 
Tue, 2012-08-28 09:30 - 11:00
Location: 
Hennings 318
Local Contact: 
Robert Raussendorf
Intended Audience: 
Graduate
The toric code and the cluster state are related in a few ways. Perhaps most straightforwardly, the toric code state can be prepared by single qubit measurements on a cluster state. The cluster state can also be used to implement topologically protected computation by simulating the braiding of topological defects in the toric code. The toric code is the simplest member of a family of models called the Kitaev quantum double models. This is a class of lattice spin models whose excitations are described by anyons.

Computation from Correlation: Putting Bell inequality violation to work

Speaker: 
Dan Browne, University College London (UK)
Event Date and Time: 
Mon, 2012-08-27 15:00 - 16:30
Location: 
Hennings 309B
Local Contact: 
Robert Raussendorf
Intended Audience: 
Graduate
The violation of Bell inequalities is perhaps the most striking example of the incompatibility of quantum physics and the classical world. Measurements on separated entangled quantum particles can be correlated in ways provably impossible if the measurements are described by any local hidden variable model. Quantum information aims to exploit the non-classical features of quantum mechanics for new technologies.

Quantum simulator using atoms and photons in a hollow core fiber

Speaker: 
L. C. Kwek, University of Singapore
Event Date and Time: 
Fri, 2012-07-20 13:30 - 14:30
Location: 
Hennings 309B
Local Contact: 
Robert Raussendorf
Intended Audience: 
Graduate
To circumvent the limitations of conventional computers in tackling complex physical processes, Richard Feynman proposed nearly thirty years ago a means of using well-understood quantum systems called quantum simulators (or quantum emulators) to emulate similar, but otherwise poorly understood, quantum systems. Among the various physical systems that could be used to build a quantum simulator, one possibility is the use of regular arrays of atoms or ions that are held in place by laser fields.

Conservation law induced limitations to quantum measurements

Speaker: 
Leon Loveridge (University of York/ UK)
Event Date and Time: 
Mon, 2012-02-27 14:00 - 15:00
Location: 
Hennings 318
Local Contact: 
Robert Raussendorf
Intended Audience: 
Graduate
The theorem of Wigner, Araki and Yanase (WAY) demonstrates that there are constraints to quantum measurements when there is an additive conserved quantity (on the Hilbert space of the system and measuring apparatus) that does not commute with the observable we wish to measure. The original theorem applied only to a restricted class of observables and conserved quantities. I'll review this theorem and its role in quantum information/computation and discuss some recent generalisations, in particular to the case of position measurements which respect the conservation of linear momentum.

Local additivity of the minimum entropy output of a quantum channel

Speaker: 
Gilad Gour (U Calgary)
Event Date and Time: 
Wed, 2012-02-22 14:00 - 15:00
Location: 
Hennings 309B
Local Contact: 
Robert Raussendorf
Intended Audience: 
Graduate
An important open problem in quantum information concerns with the question whether entanglement between signal states can help to send classical information on quantum channels. Recently, Hasting proved that entanglement does help by finding a counter-example for the long standing additivity conjecture that the minimum von-Neumann entropy output of a quantum channel is additive under taking tensor products. In this talk I will show that the minimum von-Neumann entropy output of a quantum channel is locally additive.

Optimal perfect quantum secret sharing schemes via stabilizer quantum error correcting codes and "twirling" of symplectic structures

Speaker: 
Vlad Georghiu (University of Calgary)
Event Date and Time: 
Wed, 2012-02-08 14:00 - 15:00
Location: 
Hennings 309B
Local Contact: 
Robert Raussendorf
Intended Audience: 
Graduate

 

Black Holes, Quantum information, and unitary evolution

Speaker: 
Steve Giddings (UC Santa Barbara)
Event Date and Time: 
Fri, 2012-01-13 10:00 - 11:00
Location: 
Hennings 309B
Local Contact: 
Gordon Semenoff, R. Raussendorf
Intended Audience: 
Graduate
If black hole evolution respects quantum mechanics, it should be possible to describe it in terms of unitary evolution on a Hilbert space comprising subsystems. Since such evolution must apparently violate usual locality, we seek evolution laws that generalize those of quantum field theory. I will describe some modest attempts to characterize such evolution, in a maximally conservative fashion, guided by considerations of quantum information theory and other physical constraints. A broader framework is suggested, with localization replaced by tensor factorization of Hilbert space.
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