Upcoming seminars

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

Coherence amplification by an autonomous quantum thermal machine

Seminar date and time: 
2016-09-21 14:30
Author: 
Juan MR Parrondo
Affiliation: 
Universidad Complutense de Madrid

We present a model for an autonomous quantum thermal machine comprised of two qubits that is capable of amplifying the coherence in a non-degenerate system by using only thermal resources. This novel method of coherent control allows for the interconversion between energy, both work and heat, and coherence.

 

Location: 
GIQ Seminar room

Course on "Some Elementary Remarks concerning Quantum versus Classical Statistical Physics"

Seminar date and time: 
2016-09-19 10:00 to 2016-09-21 11:30
Author: 
Jean Zinn-Justin

Dr. Zinn-Justin attended École Polytechnique for his undergraduate degree, graduating in 1964. He continued his research under Marcel Froissart at the University of Orsay, earning a Ph.D. in 1968. While Zinn-Justin has had a permanent position with the CEA-Saclay theory group, he has also held visiting positions as SUNY Stony-Brook, CERN, Princeton, Harvard, and MIT. 

Nonequilibrium thermodynamics in the strong coupling and non-Markovian regime based on a reaction coordinate mapping

Seminar date and time: 
2016-09-15 14:30
Author: 
Philipp Strasberg
Affiliation: 
Institut für Theoretische Physik, Technische Universität Berlin

We propose a method to study the thermodynamic behaviour of small systems beyond the weak coupling and Markovian approximation, which is different in spirit from conventional approaches. The idea is to redefine the system and environment such that the effective, redefined system is again coupled weakly to Markovian residual baths and thus, allows to derive a consistent thermodynamic framework for this new system-environment partition.

Location: 
GIQ Seminar room

Challenges in experimental certification in high dimensional entanglement

Seminar date and time: 
2016-09-13 14:30
Author: 
Marcus Huber
Affiliation: 
Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences (Vienna)

In this seminar I would like to present and discuss recent progress on the certification of high-dimensional entanglement. High dimensional entanglement promises to improve quantum communication protocols in numerous ways, but poses a number of challenges in its use. I will shortly present a couple of new techniques to quantify entanglement with only  limited access to measurements, and present various open problems in this context. The talk is based on past and upcoming experiments in this field [1,2], as well as a recent proposal [3]:

Location: 
GIQ Seminar room

Improved sensing with a single qubit

Seminar date and time: 
2016-07-13 14:30
Author: 
Pavel Sekatski
Affiliation: 
Institut für Theoretische Physik, Universitat Innbsbruck.

We consider frequency estimation with a arbitrary prior knowledge of the parameter. We demonstrate that a single sensing two-level system can act as a virtual multi-level system that offers increased precision in such a Bayesian frequency estimation scenario, and that allows one to estimate (arbitrary) large parameter values by avoiding phase wraps. This is achieved by making use of additional degrees of freedom or auxiliary systems not influenced by the sensing interaction.

Converse bounds for private communication over quantum channels

Seminar date and time: 
2016-07-07 15:30
Author: 
Mark Wilde
Affiliation: 
Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Center for Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803, USA

We establish several converse bounds on the private transmission capabilities of a quantum channel. The main conceptual development builds firmly on the notion of a private state [Horodecki et al., PRL 94, 160502 (2005)], which is a powerful, uniquely quantum method for simplifying the tripartite picture of privacy involving local operations and public classical communication to a bipartite picture of quantum privacy involving local operations and classical communication.

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