Upcoming seminars

Higher order interference versus quantum theory

Seminar date and time: 
2016-07-07 14:30 to 15:30
Author: 
Howard Barnum
Affiliation: 
University of New Mexico and Leibniz University Hannover

We (Ududec, Barnum, and Emerson) adapt Rafael Sorkin's hierarchy of
orders of interference in physical theories to the framework of
"general probabilistic theories", defining a notion of k-path
interference experiment and of k-th order coherence in such theories
and showing that k-th order interference in such an experiment is
equivalent to k-th order coherence between faces of the state spaces
associated with paths in the experiment. We also show that
Jordan-algebraic theories have at most second-order interference (the

Operator space and its application to Bell and steering inequalities

Seminar date and time: 
2016-07-06 14:30 to 15:30
Author: 
Zhi Yin
Affiliation: 
Wuhan University

The idea of the operator space is to quantize Banach  space, where the completely bounded map plays an important role. Due to Junge and his coauthors groundbreaking work, operator space theory was used to derive Bell inequalities with unbounded violation. In this seminar, we will recall their approach and introduce our work in steering inequalities.

No-go Conversion Witness for Two-Qudit Systems

Seminar date and time: 
2016-06-01 14:30
Author: 
Debasis Sarkar
Affiliation: 
Department of Applied Mathematics, University of Calcutta

Conversion witness provides a way to detect possible state transformation without computing monotone. The idea is a generalization to the idea of entanglement monotone. Recently, in New.J.Phys. \textbf{17}(2015) 093013 Girard et.al., have computed the form of conversion witness. We have extended the computational technique to cover more general orthogonally invariant class of states and compute the form of conversion witness. In this lecture, we will provide  few examples regarding state conversion using the new class of witnesses.

Location: 
GIQ Seminar room

Large-N-approximated field theory for multipartite entanglement

Seminar date and time: 
2016-05-31 14:30
Author: 
Giuseppe Florio
Affiliation: 
Dipartimento di Meccanica, Matematica e Management, Politecnico di Bari

We will study the properties of multipartite entanglement by adopting the concepts and tools of classical statistical mechanics. In order to explore the rich landscape that ensues, we shall make use of techniques that are based on the analysis of diagrams that naturally arise when one considers a high-temperature expansion of the distribution function of the measure of multipartite entanglement (the potential of multipartite entanglement). Unfortunately, the evaluation of the contributions of different kinds of graphs and their resummation is not a simple task.

Location: 
GIQ Seminar room

Random approximation schemes for quantum spin chains without momentum

Seminar date and time: 
2016-05-25 14:30
Author: 
Sofyan Iblisdir
Affiliation: 
University of Barcelona

A Monte Carlo exchange scheme for matrix product states is presented. It is meant as a tool towards a better understanding of mesoscopic spin chains with complex energy landscapes. The scheme is easy to implement; it operates on ensembles of configurations and couples Euclidean evolution with Metropolis moves. The resulting Markov chains are irreducible, aperiodic, sweep a compact configuration space, and half of them are reversible. As a result, eventual convergence to global minima of energy is guaranteed.

Location: 
GIQ Seminar room

The size of macroscopic superpositions is dictated by quantum mechanics itself

Seminar date and time: 
2016-05-18 14:30
Author: 
Michail Skoteiniotis
Affiliation: 
UAB - GIQ

There is nothing in the principles of quantum mechanics that excludes the possibility of preparing macrsocopic objects (such as cats, mugs, or even planets) in a superposition of two, or more, classically distinct states.  And yet we never observe such macroscopic superpositions in our everyday experience.

Location: 
GIQ seminar room

Quantum violation of the pigeonhole principle and the nature of quantum correlations

Seminar date and time: 
2016-05-12 14:30
Author: 
Sandu Popescu
Affiliation: 
Institute for Quantum Studies, Chapman University & University of Bristol

The pigeonhole principle: “If you put three pigeons in two pigeon-holes, at least two of the pigeons end up in the same hole,” is an obvious yet fundamental principle of nature as it captures the very essence of counting. Here however we show that in quantum mechanics this is not true! We find instances when three quantum particles are put in two boxes, yet no two particles are in the same box.  

Location: 
GIQ Seminar room

Entropy production and the arrow of time: how to design an optimal Maxwell's demon

Seminar date and time: 
2016-05-11 14:30 to 15:30
Author: 
Juan MR Parrondo
Affiliation: 
Universidad Complutense de Madrid

The relationship between entropy production and irreversibility can be made quantitative using the Kullbak-Leibler divergence between a process and its time reversal. This relationship allows one to bound or estimate the energy transfer between a system and its surroundings just by measuring how irreversibly the system behaves. I will show two applications of this result. The first is a technique to detect if a stationary process is consuming energy or not, something of relevance in biophysics.

Location: 
GIQ seminar room

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