Upcoming seminars

Bell Tests: investigating ``spooky action at a distance’’ in the laboratory

Seminar date and time: 
2016-11-28 13:00
Author: 
Morgan Mitchell
Affiliation: 
ICFO

I will describe briefly the nature and status of Bell tests, from their origins in the discussions between Niels Bohr and Albert Einstein, to 2015’s three loophole-free Bell tests, to the current efforts to incorporate Bell tests in communications technologies.

Location: 
Sala d'actes Edifici C

Special geometric configurations in the state space and the extremal points of the entropy of quantum measurement

Seminar date and time: 
2016-11-23 14:30
Author: 
Anna Szymusiak
Affiliation: 
Jagiellonian University, Kraków

One of the many differences between classical and quantum world is that in the classical setup we can always perform a measurement that gives certain outcomes for all pure states. Thus one can interprete the randomness of the probability distribution of the measurement outcomes as a measure of 'quantumness' (with respect to given measurement) of the initial pure state. In the talk I would like to present some special geometric configurations in the state space corresponding to the states of minimal and maximal 'quantumness' and discuss possible relations between them.
 

Location: 
GIQ - Seminar room
Contact: 

Flexible resources for quantum metrology

Seminar date and time: 
2016-11-18 14:30
Author: 
Davide Orsucci
Affiliation: 
University of Innsbruck

Quantum metrology grants a quadratic advantage over classical approaches to parameter estimation exploiting entanglement and nonclassicality. Customarily, however, the hurdle of actually implementing the necessary quantum probe states and quantum measurements is usually not taken into account, and moreover in different metrological scenarios the required states and measurements vary.

Location: 
GIQ - Seminar room

Quantifying identical-particle entanglement

Seminar date and time: 
2016-10-24 15:30
Author: 
Enrico Sindici
Affiliation: 
University of Strathclyde

Indistinguishability of particles is a counterintuitive and highly non-classical feature of quantum systems which has proven challenging to relate to standard distinguishable-particle entanglement. Inter-particle entanglement of bosons and fermions, however, plays an important role in systems with particle number superselection rules, such as atom interferometers and cold atom systems. We introduce an entanglement measure aimed at quantifying inter-particle correlations in systems with a given symmetry with respect to particle exchange.

Location: 
GIQ - Seminar Room

Fundamental limitation on quantum broadcast networks

Seminar date and time: 
2016-10-24 14:30
Author: 
Stefan Bäuml
Affiliation: 
NTT Basic Research Laboratories, NTT Corporation,

The ability to distribute entanglement over complex quantum networks is an important step towards a quantum Internet. Recently, there has been significant theoretical effort by mainly focusing on the distribution of bipartite entanglement via a simple quantum network composed only of bipartite quantum channels. There are, however, a number of quantum information processing protocols based on multipartite entanglement, rather than bipartite one, which should be served more naturally by a quantum broadcast network, rather than such a simple network.

Location: 
GIQ - Seminar Room

A histories framework for contextuality and quantum computation

Seminar date and time: 
2016-10-18 14:30
Author: 
Leonardo Disilvestro
Affiliation: 
Univ Paris-Saclay, Telecom ParisTech

In this work, we use the sum-over-histories formulation of quantum theory (a generalisation of the idea of path integrals) in order to provide two frameworks: one framework for contextuality scenarios and one framework for a specific model of quantum computation known as Measurement-Based Quantum Computation (MBQC). Using both frameworks, we re-examine the role of contextuality in the speed-up that quantum computation offers.

Location: 
GIQ Seminar room

GICQFO Meeting: Nonclassical teleportation beyond average fidelity

Seminar date and time: 
2016-10-18 11:00
Author: 
Daniel Cavalcanti
Affiliation: 
ICFO

Quantum teleportation is one the cornerstones of quantum information science, serving as a primitive in several quantum information tasks. It has become a testbed for quantum information platforms, having been demonstrated with a variety of physical systems. The benchmark for quantum teleportation is the average fidelity between the input and output states of the process. According to this figure-of-merit not all entangled states can lead to the demonstration of quantum teleportation.

Location: 
GIQ Seminar room

How does a continuously measured qubit really evolve?

Seminar date and time: 
2016-10-13 14:30
Author: 
Luis Pedro García-Pintos
Affiliation: 
Institute for Quantum Studies, Chapman University, Orange, CA, USA.

We focus on the question of what a quantum system really did during a period of time over which it was continuously monitored. First, we consider the simultaneous monitoring of two noncommuting observables---as recently implemented by the Siddiqi group at UC Berkeley---and show the manifest violation of standard inequalities for testing Leggett-Garg macrorealism. Despite this apparent lack of realism, we then construct a realistic, but epistemically restricted, model that exactly reproduces the quantum results.

Location: 
GIQ - Seminar Room

Non convexity and non additivity of channel capacities

Seminar date and time: 
2016-10-05 14:30
Author: 
Krishnakumar Sabapathy
Affiliation: 
GIQ

 I will discuss some basic aspects of non-convexity and non-additivity of quantum channel capacities. We will briefly review some known results and discuss a recent paper which prove nonconvexity of the private and environment assisted capacities as shown in arXiv:1604.07974.

Location: 
GIQ - Seminar Room

Heat and work in sequential reservoirs

Seminar date and time: 
2016-09-22 14:30
Author: 
Juan MR Parrondo
Affiliation: 
Universidad Complutense de Madrid

We present a full quantum approach to sequential (also called collisional) reservoirs using scattering states. Our analysis leads to a Boltzmann equation that satisfies detailed balance and warrants thermalization when the velocity of the reservoir atoms is Maxwellian. This approach also clarifies the energetics of the interaction identifying the energy flow between the kinetic energy of the atom as heat.

Location: 
GIQ Seminar room

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