New article: Emerging Dynamics Arising From Quantum Mechanics

Quantum Information Group @ CBPF

Title: Emerging Dynamics Arising From Quantum Mechanics

Authors: Cristhiano Duarte (UFMG), Gabriel Dias Carvalho (CBPF), Nadja K. Bernades (UFMG), Fernando de Melo (CBPF)

Link: https://arxiv.org/abs/1705.01604

Abstract: 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…

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Master dissertation defense @ CBPF: Pedro Correia — 05.05, 14h00

Quantum Information Group @ CBPF

This Friday, Pedro Correia, student at the qig@CBPF, will defend his master dissertation.
The dissertation title is “Entanglement in Coarse-grained Systems”, and it contains results on: i) coarse-grained entanglement dynamics in spin-chains, and ii) coarse-grained entanglement in micro-macro systems, with an application to the measurement problem. The details of the defense talk are below. Everyone is invited to attend it.
Boa defesa, Pedrinho!

Title: Entanglement in Coarse-grained Systems

Candidate: Pedro Correia (qig@CBPF)

Dissertation Committee: Marcelo Sarandy (UFF), Roberto Sarthour (CBPF), Gabriel Aguilar (UFRJ), Raul Vallejos (CBPF), and Fernando de Melo (CBPF).

Coordinates: Auditorium 6th floor, CBPF. 05.05, 14h00.

Abstract: In the present work we investigate the behavior of entanglement in coarse-grained systems. Our approach is basically composed of two parts.
In the first, we construct a coarse graining map that describes the entanglement dynamics in a spin-chain considering a “blurred” detection of the system. In the second part we derive…

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Talk @UFF, Carlos Eduardo R. de Souza, Friday May 5th, 11.00

This week’s talk at the Infoptics group at UFF will be given by Carlos Eduardo Rodrigues de Souza (UFF), who’ll talk on “Compressão de ruído em um oscilador paramétrico ótico com vórtices óticos” on Friday, May 5th, 11.00, in room A5-01. All are welcome! Please see an abstract below. Read the rest of this entry »


“Quantum Bayesian networks: the physics of nonlocal events”

Here is the announcement of the third event of the series: “Quantum Bayesian networks: the physics of nonlocal events”. The last one in Natal was great!

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Dear colleagues,

We are organising a workshop on quantum networks sponsored by the Foundational Questions Institute (FQXI) under the project “Quantum Bayesian networks: the physics of nonlocal events”. This will the last in a series of three workshops, the first of which took place in Barcelona (http://qbnetworks.icfo.eu/), and the second in Natal, Brazil (http://iip.ufrn.br/eventsdetail.php?inf===QTUVkM).

The workshop will take place at the Department of Computer Science (http://www.cs.ox.ac.uk) at the University of Oxford, UK on 1st-4th August 2017.

The workshop webpage is: http://www.cs.ox.ac.uk/qnetworks2017

We have the following invited speakers:

Fabio Costa (University of Queensland)
Robin Evans (University of Oxford)
Lucien Hardy (Perimeter Institute)
Matt Leifer (Chapman University)
Ognyan Oreshkov (University of Oxford)
Jacques Pienaar (IIP Natal, Brazil)
Stefano Pironio (Université Libre de Bruxelles)
Ana Belén Sainz (Perimeter Institute)
Philip Walther (University of Vienna)
Stephanie Wehner (Delft University of Technology)

In addition, we anticipate accepting additional contributed talks and posters (deadline 28th May 2017). Abstract submission is open at https://easychair.org/conferences/?conf=qnetworks2017.

Registration will be opening shortly so please check back in the coming days to register. We are also offering limited financial support to students and postdoctoral researchers. Please consult the workshop website for details.

Background: Causality is a crucial concept for our understanding of nature. In relativity, the objective properties of a system are dictated by the causal relations between events in spacetime. While quantum mechanical predictions comply with relativity, objective properties do not satisfy the same causal relations—the phenomenon known as non-locality. Quantum mechanics is consistent with special relativity at an operational level but appears to violate it at an ontological level. This reveals a deep subtlety in the way that quantum theory and relativity co-exist. Understanding this subtlety will be crucial to understanding how physical theories lead to a notion of things happening through the language of causality. The aim of the workshop is to explore all these different concepts, bringing together researchers interested in causality within quantum physics.

We look forward to seeing you in Oxford!

Antonio Acín
Rafael Chaves
Matty Hoban


Talk @UFF, Gabriel Bié Alves, Friday April 7th, 11:00

Next Friday, April 7th, at 11:00 in room A5-01, we’ll have our next group seminar at the Infoptics group at UFF. Gabriel Bié Alves, now here at UFF, will talk about “Amplificação de valores fracos e metrologia quântica”. All are welcome! Please see an abstract below. Read the rest of this entry »


New article: Coarse graining a non-Markovian collisional model

Title: Coarse graining a non-Markovian collisional model

Authors: Nadja K. Bernardes, Andre R. R. Carvalho, C. H. Monken, and Marcelo F. Santos

Journal reference: Phys. Rev. A 95, 032117 (2017)

Media cover: Time, Randomness, and Correlations in a Quantum Model

Abstract: The dynamics of systems subjected to noise is called Markovian in the absence of memory effects, i.e., when its immediate future depends only on its present. Time correlations in the noise source may generate non-Markovian effects that, sometimes, can be erased by appropriately coarse graining the time evolution of the system. In general, the coarse-graining time tCG is taken to be much larger than the correlation time τ but no direct relation between them is established. Here we analytically obtain a relation between tCG and τ for the dynamics of a qubit subjected to a time-correlated environment. Our results can be applied in principle to any distribution of the environmental correlations and can be tested through a collisional model where the qubit sequentially interacts with correlated qutrits.


Talk@UFF, 31/3, 11:00, Vasilis Kiosses (UFG)

Next Friday (31/3) at 11:00, Room A5-01, we’ll be resuming the quantum information/quantum optics talks at our Infoptics group. This week we’ll have Vasilis Kiosses (UFG) talking about “Spin and localization of relativistic fermions and uncertainty relations”. All are welcome to attend! Please see below for an abstract. Read the rest of this entry »