Upcoming seminars

Quantum versus classical correlations in Gaussian states

Seminar date and time: 
2010-07-08 13:00 to 14:00
Author: 
Gerardo Adesso
Affiliation: 
University of Nottingham

Quantum discord, a measure of genuinely quantum correlations, is generalized to continuous variable systems. For all two-mode Gaussian states, we calculate analytically the quantum discord and a related measure of classical correlations, solving an optimization over all Gaussian measurements. Almost all two-mode Gaussian states are shown to have quantum correlations, while for separable states, the discord is smaller than unity. For a given amount of entanglement, it admits tight upper and lower bounds.

Location: 
IFAE seminar room

On Quantum Channels

Seminar date and time: 
2010-06-28 09:00 to 2010-07-02 11:00
Author: 
Vittorio Giovannetti
Affiliation: 
Scuola Normale Superiore (Pisa, Italy)

These lectures are meant to provide an introduction to the theory of quantum channels, their basic properties and their applications in quantum information theory. Specifically after  reviewing some  basic facts on quantum systems, we will derive the fundamental structure of quantum channels introducing the notion of Stinespring and Kraus representation, and the Choi-Jamiolkowski isomorphism. A formal derivation of master equation evolution will also be presented. The notion of quantum capacities will then be introduced and analyzed with examples.

Location: 
aula C5b/029 / IFAE seminar room

Levitated Nano-dielectrics in the Quantum Regime

Seminar date and time: 
2010-06-17 13:00
Author: 
Oriol Romero-Isart
Affiliation: 
Max-Planck-Institut für Quantenoptik, Garching

We propose to optically levitate a dielectric nano-dielectric inside a high-finesse optical cavity in order to couple its mechanical center-of-mass motion to the optical cavity field. This opto-mechanical system has the unique feature of not

Location: 
Sala de Graus II

Zero-error capacities of quantum channels

Seminar date and time: 
2010-05-12 13:00 to 14:00
Author: 
Andreas Winter
Affiliation: 
University of Bristol & National University of Singapore

Quantum channels have all sorts of capacities: classical, quantum, private, etc. In addition, the capacity typically changes in the presence of additional resources, such as feedback, shared entanglement, etc. Very recently, quite a lot of progress was made regarding the limit of perfect communication in the above settings, at finite block length.

Location: 
Sala de Graus II (UAB, Edifici Cn)

Quantum Information and Collective Systems: Factorization vs. Frustration, Long-Distance Entanglement, and Bell Inversion Laws

Seminar date and time: 
2010-04-29 14:00 to 15:00
Author: 
Fabrizio Illuminati
Affiliation: 
Dipartimento di Matematica e Informatica, Università di Salerno

I will review some recent work carried out in Salerno on the investigation of quantum many-body systems from the viewpoint of quantum information theory. I will discuss ground state factorization and its use as a diagnostic tool to probe quantum frustrated systems. I will then review the phenomenon of long-distance entanglement in quantum spin models, some possible generalizations, and schemes of implementation in coupled cavity arrays and optical lattices.

Location: 
IFAE seminar room

Coherent transport in presence of disorder and nonlinearity

Seminar date and time: 
2010-04-13 08:30 to 09:30
Author: 
Thomas Wellens
Affiliation: 
University of Freiburg

In general, transport of waves in disordered media cannot fully be  described as a simple diffusion process, since wave interference  effects lead to a reduction or even complete suppression of the  diffusion constant (weak or strong localization) and the appearance of  a coherent backscattering peak. This talk presents a diagrammatic theory for treating the impact of  nonlinearities on these coherent transport effects. In particular, the conditions under which nonlinear effects diminish or enhance the  height of the coherent backscattering peak are discussed.

Location: 
IFAE seminar room

An area law for the entropy of low-energy states

Seminar date and time: 
2010-04-06 12:30 to 13:30
Author: 
Lluis Masanes
Affiliation: 
ICFO

It is often observed in the ground state of spatially-extended quantum systems with local inter-actions that the entropy of a large region is proportional to its surface area. In some cases, this area law is corrected with a logarithmic factor. This contrasts with the fact that in almost all states of the Hilbert space, the entropy of a region is proportional to its volume.

Location: 
IFAE seminar room

Quantum discrimination of Gaussian channels and technological applications

Seminar date and time: 
2010-03-05 15:00 to 16:00
Author: 
Stefano Pirandola
Affiliation: 
MIT & University of York

The optimal discrimination of two Gaussian channels is a central problem in quantum information theory. In this talk we discuss how the use of quantum entanglement can reduce the error probability which affects this statistical problem, giving a dramatic advantage over the use of classical light in the regime of few photons.

This enhancement is exploited in two non-trivial tasks: the detection of low-reflectivity targets (quantum illumination [1,2]) and the readout of digital memories (quantum reading [3]).

Location: 
Sala de Graus II (Campus UAB), first floor at tower C5, close to CREAF

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