[quantum-info] Talks (one today!) and Visitors

[William Matthews]

If you notice something you feel is missing from this mail,
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------ This week ------

-- Talks --

Monday, Nov 29nd, 12:30pm to 1:30pm, IQC, RAC1 Room 2009,
Mark Wilde, McGill University
Title: Entanglement boosts quantum turbo codes
Abstract: One of the unexpected breakdowns in the existing theory of quantum serial turbo coding is that a quantum convolutional encoder cannot simultaneously be recursive and non-catastrophic.  These properties are essential for a quantum turbo code to have an unbounded minimum distance and for its iterative decoding algorithm to converge, respectively.  Here, we show that the entanglement-assisted paradigm gives a theoretical and practical "turbo boost" to these codes, in the sense that an entanglement-assisted quantum (EAQ) convolutional encoder can possess both of the aforementioned desirable properties, and simulation results indicate that entanglement-assisted turbo codes can operate reliably in a noise regime 5.5 dB beyond that of standard quantum turbo codes.  Entanglement is *the* resource that enables a convolutional encoder to satisfy both properties because an encoder acting on only information qubits, classical bits, gauge qubits, and ancilla qubits cannot simultaneously satisfy them.  We give several examples of EAQ convolutional encoders that are both recursive and non-catastrophic and detail their relevant parameters.  Finally, simulation results demonstrate that interleaved serial concatenation of EAQ convolutional encoders leads to a powerful code construction with excellent performance on a memoryless depolarizing channel.

Tuesday, Nov 30th, 4:00 pm, PI, Room 301
Giacomo Mauro D'Ariano - Universita degli Studi di Pavia
Abstract: I will review some recent advances on the line of deriving quantum field theory from pure quantum information processing. The general idea is that there is only Quantum Theory (without quantization rules), and the whole Physics---including space-time and relativity---is emergent from the processing. And, since Quantum Theory itself is made with purely informational principles, the whole Physics must be reformulated in information-theoretical terms. Here's the TOC of the talk: a) Very short review of the informational axiomatization of Quantum Theory; b) How space-time and relativistic covariance emerge from the quantum computation; c) Special relativity without space: other ideas; d) Dirac  equation derived as information flow (without the need of Lorentz covariance); e) Information-theoretical meaning of inertial mass and Planck constant; f) Observable consequences (at the Planck scale?); h) What about Gravity? Three alternatives as a start for a brainstorming.

Wednesday, Dec 1st, 2:00 pm, PI, Room 405,
Sergey Bravyi - IBM T. J. Watson Research Center
Abstract: Quantum error correcting codes and topological quantum order (TQO) are inter-connected fields that study non-local correlations in highly entangled many-body quantum states. In this talk I will argue that each of these fields offers valuable techniques for solving problems posed in the other one. First, we will discuss the zero-temperature stability of TQO and derive simple conditions that guarantee stability of the spectral gap and the ground state degeneracy under generic local perturbations. These conditions thus can be regarded as a rigorous definition of TQO. Our results apply to any quantum spin Hamiltonian that can be written as a sum of geometrically local commuting projectors on a D-dimensional lattice. This large class of Hamiltonians includes Levin-Wen string-net models and Kitaev's quantum double models. Secondly, we derive upper bounds on the parameters of quantum codes with local check operators and discuss the implications for feasibility of a quantum self-correcting memory.

-- Visitors --

Giacomo Mauro D'Ariano (Universita degli Studi di Pavia) is visiting PI
until December 2nd 
hosted by Giulio Chiribella

Sergey Bravyi (IBM T. J. Watson Research Center) will be visiting PI
November 30th 2010 through December 2nd 2010
hosted by Lucien Hardy

Xie Chen (MIT) is visiting PI
November 29th 2010 through December 3rd 2010
hosted by Zhengfeng Ji

Oliver Buerschaper (Max-Planck-Institut für Quantenoptik)
December 4th 2010 through December 11th 2010
hosted by Michele Mosca

Patrick Hayden (McGill University) is visiting PI
until December 15th
hosted by Neil Turok

------ Upcoming (next 4 weeks - not exhaustive!) ------

-- Talks --

Monday, Dec 6th, 4:00 pm, PI, Room 301
Oliver Buerschaper
"Classifying Topological Order: Dualities and Hierarchies"

Wednesday, Dec 7th, 2:00pm, PI, Room 405
David Cory
Colloquium (Title TBA)

-- Visitors --

Lianao Wu (University of the Basque Country)
December 6th 2010 through December 18th 2010 
hosted by Daniel Gottesman