Candidata: Isadora Barbosa Lima Veeren,
Título da dissertação: Entropic uncertainty relations and classicality
Coordenadas: 30 de Abril às 16h. CBPF, auditório do sexto andar.
Banca: Fernando de Melo (CBPF), Bárbara Amaral (UFSJ*), Daniel Schneider Tasca (UFF), Ivan de Oliveira (CBPF) e Roberto Sarthour (CBPF).
Estão todxs convidadxs!
*não poderá participar.
Título: Como confiar nas tecnologias quânticas de muitos corpos?
Palestrante: Mario Leandro Aolita (UFRJ)
Coordenadas: sala 601C, CBPF. 04/04, 16h00
Resumo: Recentemente houve um progresso experimental impressionante em tecnologias quânticas de muitos corpos. No entanto, ainda não temos ferramentas práticas de certificação que nos permitam garantir se os dispositivos quânticos experimentais que construímos funcionam adequadamente. De fato, uma vez que a simulação clássica de sistemas quânticos é uma tarefa computacionalmente difícil — exponencial no número de partículas — o paradigma usual de “predizer e comparar com o experimento” torna-se inaplicável. Este é um dos maiores obstáculos para as tecnologias quânticas de grande escala. Neste seminário, falarei sobre avanços recentes na validação de computadores quânticos e simuladores quânticos de muitos corpos. Em particular, discutirei testemunhas de fidelidade para simulações quânticas de bosons e para cadeias de spins, computação quântica verificável e tomografia de estado quântico assistida por redes neurais nativas de aprendizado de máquina sem supervisão.
Title: Spin-entanglement wave in a coarse-grained optical lattice
Authors: Pedro Silva Correia, Fernando de Melo
Abstract: In the present work we explore a suitable coarse graining channel as a tool to describe entanglement spreading in a coarse-grained spin-chain with different degrees of resolution. Comparing with the experimental realizations performed with ultracold atoms, our results suggest that even if we are not able to fully resolve the system, entanglement can still be detected for some coarse graining levels. Furthermore, we show that it is possible to have some information about the “microscopic” entanglement, even if we have access only to the system’s coarse graining description. We show that the amount of entanglement decays exponentially with the lack of system resolution. The lack of experimental resolution might thus lead to a classical effective description.
The year is about to finish… but we continue full power. This week our series of seminars QM Talks@CBPF, have the pleasure to welcome Alexis Hernández, from the Federal University of Rio de Janeiro. Alexis has many interests within physics (and outside of it as well!). This time he’ll tell us about a nonlinear description of Hall voltages. See details below.
Title: Investigating transverse Hall voltages using two-terminal setups
Speaker: Alexis Hernández (UFRJ)
Coordinates: room 601C, CBPF. 06/12, 16h00
Abstract: In this talk, we present a method to numerically study transverse Hall voltages using an alternative quantity in two-terminal setups. Using nonlinear transport concepts, we find that the Hall voltage dependence on the model parameters can be investigated from the difference between the injectivities of each terminal. The method is suitable to work with nonequilibrium Green’s functions as well as for scattering matrix approaches. We illustrate the proposed idea by studying the quantum spin Hall effect in graphene with disordered spin-orbit scattering centers induced by adatoms. We use two distinct models: a finite-difference implementation of the Dirac Hamiltonian and a tight-binding Hamiltonian combined with the scattering matrix approach and the nonequilibrium Green’s functions approach, respectively.
The 2018 Physics Nobel Prize was awarded “for groundbreaking inventions in the field of laser physics”. Among these inventions are the optical tweezers, which will play an important role in our next QM Talks@CBPF. This week we are pleased to welcome Diney Ether (UFRJ), who is employing optical tweezers to measure very feeble forces due to the Casimir effect. See details below, and be sure to be there!
Title: Perspectives: Probing the Casimir Effect using Optical Tweezers
Speaker: Diney Ether (UFRJ)
Coordinates: room t.b.a, CBPF. 10/10, 16h00
We propose to use optical tweezers to probe the Casimir interaction between microspheres inside a liquid medium. This setup has the potential for revealing unprecedented features associated either with the Casimir force screening by movable ions in solution and the non-trivial role of the spherical curvatures achieved by going beyond the validity of the widely employed proximity force approximation. We will show some current experimental results with polystyrene microspheres immersed in water at distances below 500nm by employing very soft optical tweezers, with stiffness in the scale of fN/nm. Finally, we also described some theoretical results and future perspectives to suppress the electrostatic double-layer force always present in this context, and some theoretical results concerning light reverberation between the microspheres. This line of investigation has the potential for bringing together different fields including classical and quantum optics, statistical physics and colloidal science, while paving the way for novel quantitative applications of optical tweezers in cell and molecular biology.
D. S. Ether, L. B. Pires et al, EPL 112, 44001 (2015).
D. S. Ether, F. S. S. Rosa et al, PRE 97, 022611 (2018).