Upcoming seminars

Coherence power of quantum evolutions

Seminar date and time: 
2015-12-18 14:30
Author: 
María García Díaz
Affiliation: 
Ulm

The structure of the environment in which an open system is embedded determines its coherence capabilities. Whether these can result in any functional advantage remains an open question. The resource theory of coherence is a convenient framework to investigate these issues. Through the definition of the coherence power we will explore the ability of unitary operators to generate coherence. We will also introduce non-unitary time evolutions as quantum channels whose coherence capabilities it would be of interest to compute.

 

Criticality and general quantum correlations:
 Reasons to study quantum discord

Seminar date and time: 
2015-12-02 14:30
Author: 
Steve Campbell
Affiliation: 
School of Mathematics and Physics, Queen's University Belfast

The study of quantum correlations has significantly progressed in recent years. An interesting measure proposed, and one that still proves divisive, is the quantum discord. In this talk I will show some advantages that arise when discord and discord inspired measures of general quantum correlations are carefully put to good use. In particular when examining inherently quantum mechanical phenomena, i.e. quantum phase transitions in simple spin models.

Ultimate Limits of quantum metrology assisted by error correction and fast control

Seminar date and time: 
2015-11-24 14:30
Author: 
Michalis Skotiniotis
Affiliation: 
Institute for Theoretical Physics, University of Innsbruck

We consider ultimate limits on how precise a parameter, such as frequency or magnetic field strength, can be estimated in the presence of general noise.  We show that the usage of full quantum control, in particular of auxiliary systems and fast continuous quantum error correction, allows one to improve the achievable accuracy. When an overall Hamiltonian description is appropriate, we find that a quadratic improvement (Heisenberg scaling) is achievable for all kinds of noise except noise generated by the Hamiltonian to be estimated.

Non-local order in a fermionic chain with extended correlated hopping

Seminar date and time: 
2015-11-19 14:30
Author: 
Julia Stasińska
Affiliation: 
Postdoctoral Researcher ICFO - The Institute of Photonic Sciences

I will discuss a non-standard Hubbard model with next-nearest-neighbour correlated hopping which describes ultracold fermions in a one-dimensional, spin-dependent, optical lattice. We provide an exact non-trivial, solution to this many-body model, which is independent of known exact solutions in 1-d systems. The solution reveals the general properties of this system for arbitrary filling: exact and asymmetric spin-charge separation, a gapless spectrum of lowest energy excitations, a spin-gap and a non-vanishing string correlator, which signals the presence of the non-local order.

Location: 
(Sala de Graus II to be confirmed)
Contact: 
julia.stasinska@icfo.es

Quantum capacities for nice channels

Seminar date and time: 
2015-11-16 14:30
Author: 
Marius Junge
Affiliation: 
University of Illinois at Urbana-Champaign, Department of Mathematics.

In this talk we will combine vNa and operator space tools to give estimates for the regularized and potential capacity of a channel. Joint with Gao and Laracurente

Location: 
(To be announced on Monday)
Contact: 
mariusjunge@gmail.com

Verifying multipartite entanglement in semi-device independent settings.

Seminar date and time: 
2015-11-12 14:30
Author: 
Will McCutcheon
Affiliation: 
University of Bristol, Faculty of Engineering

We'll discuss an entanglement verification protocol that allows any party in a network to check if a source is distributing a genuinely multipartite entangled state, even in the presence of distrustful parties and loss. The protocol remains secure against dishonest behavior of the source and other parties, including the use of system imperfections to their advantage. We demonstrate the verification protocol in a three- and four-party setting using polarization-entangled photons, thus highlighting its potential for realistic quantum communication and networking applications.

Stahl's Theorem (aka BMV Conjecture): Insights and Intuition on its Proof and Applications

Seminar date and time: 
2015-11-04 14:30
Author: 
Fabien Clivaz
Affiliation: 
University of Geneva

The Bessis-Moussa-Villani conjecture states that the trace of exp(A-tB) is, as a function of the real variable t, the Laplace transform of a positive measure, where A and B are hermitian matrices. The long standing conjecture was recently proven by Stahl and streamlined by Eremenko. We report on that proof and recall the significance of the result when approximating the energy of perturbed quantum mechanical systems.

Converting quantum resources: the cases of coherence, discord, and entanglement

Seminar date and time: 
2015-11-03 14:30
Author: 
Gerardo Adesso
Affiliation: 
University of Nottingham

Coherence, discord-type correlations, and entanglement are all fundamental manifestations of quantum theory and are all useful resources for certain quantum technological tasks. In this talk I show how these different signatures of quantumness can be converted into each other and interpreted under a common framework. I first review the rigorous mapping between discord-type measures and entanglement measures by means of premeasurement interactions, recently implemented experimentally.

Pages

Campus d'excel·lència internacional U A B