Upcoming seminars

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.

Beating the shot-noise limit at finite temperatures with many-body systems

Seminar date and time: 
2016-03-16 14:30
Author: 
Mohammad Mehboudi
Affiliation: 
GIQ - UAB

Parameter estimation in strongly correlated systems is gaining an increasing attention, due to the crucial role of the value of such parameters in determining the (phase) behaviour of many body systems. In this work we deal with the estimation of coupling constants of such systems at finite temperatures. To this end we use tools from quantum metrology and find the ultimate precision of estimation allowed by quantum mechanics.

Markovianization of tripartite quantum states and its application to distributed quantum computation

Seminar date and time: 
2016-03-11 15:30
Author: 
Eyuri Wakakuwa
Affiliation: 
The University of Electro-Communications, Chofu (Japan)

We introduce a task that we call Markovianization, in which a tripartite quantum state is transformed to an approximate quantum Markov chain by a random unitary operation on one of the three subsystems. We consider an asymptotic limit of infinite copies and vanishingly small error, and define the Markovianizing cost as the minimum cost of randomness per copy required for the task.

The second law of quantum thermodynamics as an equality

Seminar date and time: 
2016-03-11 14:30
Author: 
Jonathan Oppenheim
Affiliation: 
University College London

The traditional second law of thermodynamics says that the average amount of work required to change one state into another while in contact with a heat reservoir,  must be at least as large as the change in free energy of the system. Here, we consider a fine-grained notion of the free energy, and show that in terms of it, the second law can be written as an equality. We also obtain a generalisation of the Jarzynski fluctuation theorem which holds for arbitrary initial states, not just the case of an initial thermal state. These can be derived from a fully quantum parent identity.

Channel adapted decoding strategies based on complementarity

Seminar date and time: 
2016-02-25 15:30
Author: 
Alvaro Piedrafita
Affiliation: 
ETH

Focus on recovering classical and phase information is a structured way of decoding. This complementarity decoder has shown high performance when tested with different kinds of codes, outperforming strategies based on recovering from errors. We hope that the structured nature of the recovery operation might lead to implementable decoding schemes.

Heisenberg-Weyl basis observables and their application in entanglement detection

Seminar date and time: 
2016-02-25 14:30
Author: 
Claudio Kloeckl
Affiliation: 
UAB - GIQ

Bloch vectors provide a very useful geometrical representation of quantum states for characterizing their properties. We establish a new basis of observables constructed by a suitable combination of the non-Hermitian generalization of the Pauli matrices, the Heisenberg-Weyl operators. This allows us to identify a (Hermitian) Bloch representation for an arbitrary density operator of finite, as well as infinite dimensional systems in terms of complete set of Heisenberg-Weyl observables.

Lecture on asymptotic geometric analysis

Seminar date and time: 
2016-02-24 14:30
Author: 
Cécilia Lancien
Affiliation: 
UAB - GIQ and Institut Camille Jordan, Université Claude Bernard Lyon 1

This lecture will revolve round some applications of asymptotic geometric analysis (fancy name, but don't worry it's not so terrible as it sounds!) in quantum information theory. Depending on the preferences of the audience, the main focus of the lecture could be on one of the following topics:

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