Upcoming seminars

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

Dependent Component Analysis

Seminar date and time: 
2016-04-28 14:30
Author: 
Janis Nötzel
Affiliation: 
GIQ - UAB

We present an information-theoretic analysis of a question right at the heart of unsupervised learning approaches:
Assume we are collecting a number K of observations about some event E from K different agents. Can we infer E from them without exactly knowing the behaviour of each of the agents? We model this task by letting the events be distributed according to a distribution p and the task is to estimate p under unknown and independent noise. It turns out that this task is feasible if

Location: 
GIQ Seminar room

Quantum walks

Seminar date and time: 
2016-04-27 14:30
Author: 
Mark Hillery
Affiliation: 
Department of Physics, Hunter College of CUNY

A quantum walk is a quantum version of a classical random walk.  The walk can take place on a line or on a more general structure, a graph.  There are three different versions of quantum walks, coined walks and scattering walks, both of which are discrete-time walks, and continuous-time walks.  Quantum walks have proven useful in search problems, where the task is to find a particular, marked vertex in a graph, and a quantum walk can find such a vertex with a quantum speedup.

Location: 
GIQ seminar room

Achievable Rates in Cognitive Quantum Interference Channel

Seminar date and time: 
2016-04-20 14:30
Author: 
Zahra Baghali Khanian
Affiliation: 
UAB - GIQ

In the classical setting, cognitive radio channel is defined as an interference channel in which some senders obtain the encoded messages of the other senders and plan to transmit. We define a generalization of classical cognitive radio channel as a quantum interference channel with two classical inputs and two quantum outputs in which Sender 2 (cognitive sender) obtains the encoded message of Sender 1 in a non-casual manner.

Location: 
GIQ seminar room

Quantification of bound entanglement in two-qutrit states

Seminar date and time: 
2016-03-16 15:30
Author: 
Gael Sentís Herrera
Affiliation: 
Centros de Bizkaia

A bipartite system may be in an entangled state albeit its partially transposed density matrix has only nonnegative eigenvalues. Such states are known to be bound-entangled -no singlet entanglement can be distilled from them-, and constitute a subject of continued interest in quantum information. As bound-entangled states in general are highly mixed the exact quantification of their entanglement in terms of established entanglement measures has remained an open question, and only numerical bounds were known.

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