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

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 an equation of motion for entanglement in 2×D systems, when the second subsystem undergoes an arbitrary channel. Finally, considering as the channel in this equation the coarse-graining map created in the first part, we are able to investigate the measurement process, when a detector (macroscopic object) interacts with a quantum system. Then we see how entanglement behaves as the detector increases.

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New article: Vestiges of quantum oscillations in the open evolution of semiclassical states

Title: Vestiges of quantum oscillations in the open evolution of semiclassical states

Author: Alfredo M. Ozorio de Almeida (qig@CBPF)

Link: https://arxiv.org/abs/1703.08533

Abstract: A single wave component of a quantum particle can in principle be detected by the way that it interferes with itself, that is, through the local wave function correlation. The interpretation as the expectation of a local translation operator allows this measure of quantum wavyness to be followed through the process of decoherence in open quantum systems. This is here assumed to be Markovian, determined by Lindblad operators that are linear in position and momentum. The limitation of small averaging windows and even smaller correlation lengths simplifies the semiclassical theory for the evolving local correlation. Its spectrum has a peak for each classical momentum, subjected to Gaussian broadening with decoherence. These spectral lines can be clearly resolved even after the Wigner function has become positive: The correlations located far from caustics seem to be the last vestige of quantum oscillations.

QM Talks@CBPF: Alex Bouvrie — 29.03, 16h00

We resume our series of seminars with a talk by Alex Bouvrie, a postdoc here in the qig@cbpf. Indeed, Alex has just being awarded a new postdoc fellowship (PCI), which will allow him to stay a little longer with us. Luckly for us!

This time he’ll tell us about his latest results on composite fermions, and how the entanglement between them explains some features of experiments producing  Bose-Einstein condensates with fermions… got confused? Check out the details of his talk below,  and see you there!

 

Title: Quantum information in ultracold interacting Fermi gases

Speaker: Alex Bouvrie (CBPF)

Coordinates: room 601C, CBPF. 29.03, 16h00

Abstract: Recently the quantum information group of the CBPF showed that the application of the composite bosons theory [1] to ultracold  interacting Fermi gases is remarkable [2,3]. The effects of the underlying fermionic structure of composite bosons (molecules made from two fermions) formed in two-component Fermi gases, are well described by this theory in the strong binding regime and are reflected in experimentally measurable observables  [2]. For example, the fraction of ground state molecules in an interacting Fermi gas, i.e. the (Bose-Einstein) condensate fraction, depends on the entanglement created by the Feshbach induced interaction between the fermions that make up the molecules. Different fermion species interact via Feshbach resonance and fermion pairs interact among them via Pauli principle or fermion exchange interaction. Ultracold interacting Fermi gases are, therefore, strongly correlated (entangled) systems. In this seminar we will present our latests results [1] and show that the theory of composite bosons can be a useful tool to theoretically describe these quantum correlations. We will also show that Pauli correlations between fermion pairs (molecules) are essential to preserve the quantum coherence of the condensate in beam-splitter dynamics and how to generate entangled Bose-Einstein condensates  with these dynamical processes [3].

[1] M. Combescot, O. Betbeder-Matibet, and F. Dubin, Phys. Rep. 463, 215 (2008)
[2] P. Alexander Bouvrie, Malte C. Tichy, and Itzhak Roditi, Phys. Rev. A 95, 023617 (2017)
[3] P. Alexander Bouvrie, Malte C. Tichy, and Klaus Mølmer, Phys. Rev. A 94, 053624 (2016)

 

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Paraty VI: Registration is open!

quantum Rio

The time has come… again. The sixth edition of the Quantum Information School and Workshop is accepting applications.

In this edition we will be celebrating 10 years from the first “Quantum Paraty”. Ten years have passed but the relaxed atmosphere — great science, long lunch breaks, friendly people, a boat trip instead of the boring usual conference dinner, and Paraty itself –, that build up the reputation of Paraty as the coolest quantum information conference in the world, continue as our commandment. Ask people about it and register! All the info and registration form can be found in the conference webpage http://paratyquantum.info.

See you in Paraty!

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Open postdoc positions

The Brazilian Center for Research in Physics (CBPF), a research unit of the Ministry of Science, Technology, Innovations and Communications (MCTIC), has openings for 13 postdoctoral scholar positions in various research topics. The topics include quantum information, both theory and experiment.

Interested candidates can find information about the call at http://portal.cbpf.br/chamada-publica-pci-2016.

Contact us if you are willing to join our quantum information group as postdoc!

Quantum Rio Workshop, Dec. 7/8th

quantum Rio

Next week, on December 7th and 8th, in CBPF (at the 6th floor auditorium), we’ll have our first Quantum Rio Workshop, an informal gathering of the quantum information community in and around Rio, organized by Malena Hor-Meyll (UFRJ), Roberto Sarthour (CBPF) and Ernesto Galvão (UFF).

The idea of the workshop is to foster more interaction and collaboration among the quantum information/quantum optics researchers in the area. We’ve allocated half-hour talk slots to some of the group leaders, complemented by posters and coffee during the talk breaks, mostly by students (please encourage them to contribute!). The workshop will be financed by workshop fees (paid only by professors).

Please find the schedule below:

Wednesday, Dec. 7th:
9:00-09:30 Luiz Davidovich
9:30-10:00 Fernando Melo
10:00-10:30 coffee
10:30-11:00 Gabriel Aguilar
11:00-11:30 Alexandre Souza
11:30-12:00 Ernesto Galvão
12:00-14:00 lunch
14:00-14:30 José Augusto Huguenin/Alexandre Schmidt
14:30-15:00 Mohammad Rajabpour
15:00-16:00 coffee/posters
16:30-17:00 Marcelo França
17:00-17:30 Leandro Aolita
Thursday, Dec…

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QM Talks@CBPF: Yelena Guryanova — 30.11, 16h00

Title: Thermodynamics of quantum systems with multiple conserved quantities

Speaker: Yelena Guryanova (IQOQI- Institute for Quantum Optics and Quantum Information)

Coordinates: room 601D, CBPF. 30.11, 16h00

Abstract: We consider a generalisation of thermodynamics that deals with multiple conserved quantities at the level of individual quantum systems. Each conserved quantity, which, importantly, need not commute with the rest, can be extracted and stored in its own battery. Unlike in standard thermodynamics, where the second law places a constraint on how much of the conserved quantity (energy) that can be extracted, here, on the contrary, there is no limit on how much of any individual conserved quantity that can be extracted. However, other conserved quantities must be supplied, and the second law constrains the combination of extractable quantities and the trade-offs between them which are allowed. We present explicit protocols which allow us to perform arbitrarily good trade-offs and extract arbitrarily good combinations of conserved quantities from individual quantum systems.