Seminars
June 22nd, 2017 NADJA K. BERNARDES, Federal University of Minas Gerais ROMAN ORÚS, Johannes Gutenberg-Universität, Mainz
MARCO TULIO QUINTINO, Université de Genève

NADJA K. BERNARDES ’Emerging Dynamics Arising From Quantum Mechanics’

Physics dares to describe Nature from elementary particles all the way up to cosmological objects like cluster of galaxies and black holes. Although a unified description for all this spectrum of events is desirable, an one-theory-fits-all would be highly impractical. To not get lost in unnecessary details, effective descriptions are mandatory. Here we analyze what are the dynamics that may emerge from a fully quantum description when one does not have access to all the degrees of freedom of a system. More concretely, we describe the properties of the dynamics that arise from Quantum Mechanics if one has only access to a coarse grained description of the system. We obtain that the effective channels are not necessarily of Kraus form, due to correlations between accessible and non-accessible degrees of freedom, and that the distance between two effective states may increase under the action of the effective channel. We expect our framework to be useful for addressing questions such as the thermalization of closed quantum systems, and the description of measurements in quantum mechanics.


ROMÁN ORÚS ’Tensor Networks for Quantum Matter: Basics, News and Prospects’

Tensor network states have established themselves as the natural language based on entanglement to describe and numerically simulate quantum many-body systems. In this talk I will first provide a long introduction to what tensor network states are, as well as to some of their related numerical methods. An overall perspective on the field will also be provided. Then, I will review recent progress on this topic conducted in my group. In particular, I will focus on the study of (i) 2d topological order, and (ii) Kagome Heisenberg antiferromagnets on a field, but other relevant developments may also be briefly discussed. Finally, I will discuss future research directions including the role of tensor networks in AdS/CFT, lattice gauge theories, many-body localization, and other recent ideas.


MARCO TULIO QUINTINO ’Device-Independent Certification of a General Measurement Incompatibility Structure’

Incompatibility of quantum measurements lies in the core of quantum mechanics and it is a fundamental ingredient for many quantum information protocols. In this talk we explore the concept of Joint Measurability and Bell nonlocality to analyse measurement incompatibility in a device independent way. In simple words, a set of measurements is called jointly measurable if they can be measured simultaneously, i.e. , if there exists a single measurement that can be used to recover the information about all the measurements in the set as marginals. Standard violation of a Bell inequality certifies measurement incompatibility but it does not state anything about the incompatibility structure of the measurements. For instance, one cannot ensure pairwise incompatibility just with a standard violation of a three measurement Bell inequality. In our work we construct a systematic method to certify a general joint measurability structure in a device independent way. We illustrate these methods by analysing the scenario of three choices of measurements per party, by presenting new Bell inequalities that certify some particulars joint measurability structures, and by discussing an interesting phenomenon where one can certify pairwise incompatibility but one cannot say which pair is incompatible. We end the talk by presenting results on semi-device independent certification of a general joint measurability structure by exploring Einstein-Podolski-Rosen-steering nonlocality.


Seminar, June 22, 2017, 14:30. Blue Lecture Room

Hosted by Prof. Antonio Acín and Prof. Maciej Lewenstein

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