Colóquios e Seminários

Café com Física Especial – Quantum Information Science with Trapped Ca+ Ions

In this talk, the basic toolbox of the Innsbruck quantum computer based on strings of trapped Ca+ ions will be reviewed [1] and an overview will be given on our current experiments in the field of quantum information science.

For quantum information processing, the toolbox operations are used to encode one logical qubit in entangled states distributed over seven trapped-ion qubits. We demonstrate the capability of the code to detect one bit flip, phase flip or a combined error of both, regardless on which of the qubits they occur.

Furthermore, we apply combinations of the entire set of logical single-qubit Clifford gates on the encoded qubit to explore its computational capabilities [2].

With the quantum toolbox both analog and digital quantum simulations are carried out [3].

The basic simulation procedure will be presented and its application will be discussed for a variety of spin Hamiltonians.

Including a carefully controlled dissipation mechanism, the toolbox even allows for the quantum simulation of open systems [4].

With long ion strings, the quantum toolbox is applied to investigate the propagation of entanglement in a quantum many-body system represented by the trapped-ion qubits [5].

[1] P. Schindler et al., New. J. Phys. 15, 123012 (2013).

[2] D. Nigg, M. Müller et al., Science 345, 302 (2014).

[3] R. Blatt and C. F. Roos, Nature Phys. 8, 277 (2012).

[4] J. T. Barreiro et al., Nature 470, 486 (2011).

[5] P. Jurcevic, et al., Nature 511, 202 (2014).

Prof. Rainer Blatt – Institute for Experimental Physics – University of Innsbruck – Institute for Quantum Optics and Quantum Information – Austrian Academy of Sciences.

Seminário do Grupo de Óptica: “Ressonâncias de Fano no espalhamento de luz por nanopartículas”

A ressonância de Fano, descoberta no ramo da física atômica por Ugo Fano, é uma característica marcante de sistemas quânticos abertos. Sendo um fenômeno de interferência, essa ressonância também se manifesta em óptica clássica e pode ser descrita dentro do formalismo de Lorenz-Mie. Com os avanços técnicos na engenharia de nanoestruturas plasmônicas e metamateriais, o “efeito Fano” tem se tornado uma importante ferramenta para o controle das interações dos modos eletromagnéticos no espalhamento de luz por nanopartículas. Graças ao perfil assimétrico da ressonância de Fano, que possui um pico de ressonância muito próximo espectralmente de uma antirressonância, sistemas exibindo o efeito Fano são altamente sensíveis ao ambiente dielétrico local. De fato, a interferência entre os modos reemitidos pelo centro espalhador no dielétrico circundante pode dar origem tanto ao aumento de intensidade do campo eletromagnético próximo quanto à sua supressão ressonante. Neste seminário, abordaremos algumas das modernas aplicações envolvendo ressonâncias de Fano em plasmônica, bem como resultados teóricos que publicamos recentemente acerca deste tema .

T. J. Arruda, F. A. Pinheiro e A. S. Martinez, “Electromagnetic energy within coated spheres containing dispersive metamaterials.” J. Opt., 14 (065101), 2012.

T. J. Arruda, A. S. Martinez e F. A. Pinheiro, “Unconventional Fano effect and off-resonance field enhancement in plasmonic coated spheres,” Phys. Rev. A, 87 (043841), 2013.

T. J. Arruda, F. A. Pinheiro e A. S. Martinez, “Electromagnetic energy within single-resonance chiral metamaterial spheres,” J. Opt. Soc. Am. A, 30:1205-1212, 2013.

T. J. Arruda, A. S. Martinez e F. A. Pinheiro, “Electromagnetic energy within coated cylinders at oblique incidence and applications to graphene coatings,” J. Opt. Soc. Am. A, 31:1811-1819, 2014.

T. J. Arruda, A. S. Martinez e F. A. Pinheiro, “Omnidirectional absorption and off-resonance field enhancement in dielectric cylinders coated with graphene layers,” J. Opt. Soc. Am. A, 32: 943-948, 2015.

Seminário: “Multi-chanel MRI”

Transmitting and receiving radio frequency signals for NMR signal excitation and response has been developed since the first crossed-pair coils used by Bloch for his co-discovery (together with Purcell) of NMR in 1945. In a more modern sense using multiple transmit and receive channels in parallel to acquire more signal from more volume, and/or to target specific regions of interest more optimally, multi-channel MRI has been under development and in practice since my presentation of “Parallel Imaging for MRI” in poster at the 1986 New York Academy of Science meeting. Of course multi-channel receive arrays, and parallel imaging with them, took off with Pete Roemer’s patent in 1989 followed by the advent of parallel imaging from Sodickson’s SMASH in 1996 followed by Pruessmann’s SENSE techniques, and still represent the State-of-the-Art in clinics today. All the while, multi-channel transmit approaches to solve problems and enhance performance especially for ultra-high field MRI have been pursued by myself and others since the first 2T system in 1984. In 1992 and since I have demonstrated both the need for and the application of what is known today as B1 shimming. I have used this term to more broadly apply to the ability and utility of manipulating the RF EM field generated by a coil, over five degrees of freedom (phase, magnitude, frequency, space, time), by adjusting the currents on multiple, independent coil elements or channels accordingly. Multi-channel transmit demonstrated use and potential for optimizing RF field uniformity, SAR, SNR, transmit efficiency, speed, and other benefits, especially important in modern, ultra-high field MRI where the shorter Larmor wavelengths are leading to increasing interference patterns and loss adversely effecting the success and safety of human studies. Additional avenues of multi-channel MRI development in our lab include on-coil, channel dedicated RF/analog front-ends and channel dedicated, FPGA facilitated, automated tune, match, and isolation functions for the ultimate versatility and optimization of RF technology and techniques for MRI. Finally, new research in simulation and validation of multi-channel RF safety principles and practices will be presented.

Seminário do Grupo de Cristalografia: “New methodologies for examining neuronal ensembles”

When using drugs of abuse, learned associations are formed between the drugs and stimuli present in the drug-taking environment. With continued use, these stimuli can become cues that promote drug relapse. We have identified sparsely distributed patterns of neurons in the brain called ‘neuronal ensembles’ that are selectively activated by drug-related cues and thought to encode the learned associations that mediate drug seeking behavior. The talk will discuss new approaches — Daun02 inactivation, FACS sorting of activated neurons, Fos-GFP and c-Fos-Tetop::iCre transgenic rats — that have been used to selectively target and study activated neuronal ensembles in models of conditioned drug effects and relapse.

High energy physics seminars: “Phenomenology of new heavy quarks at the LHC”

New heavy quarks are predicted in various scenarios of new physics; depending on their nature they can mix with SM quarks or they can even mediate the production of dark matter states. Theoretically-motivated scenarios of new physics in general predict the

existence of multiple new quarks with different couplings with the SM states or dark matter. Experimental searches of new quarks at the LHC, on the other hand, have so far mostly tested minimal extensions of the SM with new quarks which specific decay patterns. No signals have been detected, pushing mass limits above 600-800 GeV, depending on different assumptions about their couplings to SM states. The reinterpretation of mass bounds from experimental searches to test theoretical models is therefore not always straightforward.

Para informações sobre os próximos seminários, acesse

http://www.ifsc.usp.br/~lattice/hepseminar/

I will describe model independent methods to recast data from experimental searches. These methods can be used to test general scenarios with any number of extra quarks which can mix with all SM families or couple to dark matter.

Journal club: “Glycerol Adsorption on Platinum Surfaces: A Density Function Theory Investigation”

Several studies have suggested glycerol as a candidate for hydrogen production (C3H5(OH)3 + 3H2O ⟶ 3CO2 + 7H2, ΔH = 225.29 kJ/mol). The promising results of steam reforming of glycerol on the Pt, Pd, Ni and Cu-based materials have been obtained in several experimental studies, however, the interaction mechanism between glycerol and transition-metal surfaces is still not well-understood. In this talk, the interaction mechanism between glycerol and Pt surfaces along with the adsorption, structural and electronic properties of glycerol on (111), (100), (110) Pt surfaces will be discussed based on initio dispersion corrected density functional theory calculations [1]. Moreover, the role of the defects on the Pt surface on the adsorption properties of glycerol will be also highlighted [2].

The obtained results play an important role on improvement of our basic understanding of the interaction of glycerol molecule with open and close-packed Pt surfaces and the surface with defects, which can help in design of new catalysts for glycerol reforming reaction.

[1] P. Tereshchuk and J. L. F. Da Silva, J. Phys. Chem. C 118, 15251 (2014).

[2] P. Fernandez, J. F. Gomes, C. A. Angelucci, P. Tereshchuk, C. A. Martins, G. A. Camara, M. E. Martins, J. L. F. Da Silva, G. Tremiliosi-Filho, ACS Catalysis 5, 4227 (2015).

Astro-Cosmo-Particle Journal Club: “Teste da invariância de Lorentz com raios cósmicos”

Nosso objetivo é reunir estudantes e cientistas interessados em discutir temas relevantes da física de partículas, cosmologia e astrofisica de partículas. Todos estão convidados a participar das reuniões, mas aconselhamos que se leia o artigo com antecedência, para que se possa acompanhar a discussão.

O artigo escolhido para próxima discussão pode ser acessado no endereço eletrônico http://iopscience.iop.org/1475-7516/2009/04/022

Café com física: “Frequency- and Gradient-Modulated MRI: Imaging with Extreme Field Inhomogeneity”

MRI has evolved into an incredibly powerful tool due to impressive innovations over the past 3-4 decades. However, the general approach used to obtain MR images has not deviated significantly from Lauterbur’s original MRI experiment (1). That is, in state-of-the-art MRI, the pulse sequence used to generate spatially-encoded signals for imaging requires two basic elements: a sufficiently short RF pulse to excite all resonance frequencies of interest simultaneously, followed by a finite time during which magnetization is allowed to evolve in the presence of a field gradient to encode their spatial locations. This universal approach to MR imaging is optimal only under stringent experimental conditions. Specifically, frequency variation due to field inhomogeneity and magnetic susceptibility must be limited to a small fraction of the Larmor frequency, γB0. Although recent advances have improved the ability of Fourier-based imaging to tolerate B0 inhomogeneity, these improvements fall short of meeting the technical requirements for human imaging using small and portable magnets. For example, MRI of the human brain cannot be performed with the subject’s body from the shoulder down placed outside the magnet bore. No MRI technology has ever been conceived to accomplish this; that is, until possibly recently. Namely, spatiotemporal encoding (2-7) has the capability to go far beyond standard Fourier imaging in terms of tolerating B0 inhomogeneity, allowing B0 to vary by a significant fraction of the nominal field.

Improved tolerance to B0 inhomogeneity with spatiotemporal-encoded MRI has already been demonstrated by us and others. However, these improvements were limited because B0 compensation was restricted to one or possibly two spatial directions simultaneously. Now, due to the recent invention of 3D frequency-swept excitation pulses in STEREO (7), in combination with parallel transmit “beam-steering”, multi-coil shimming, and simultaneous transmit and receive electronics, it should be possible to fully compensate extreme B0 inhomogeneity and thus accomplish MR imaging of brain using a small and portable head-only magnet. STEREO, which stands for steering resonance over the object (7), produces non- Fourier based images by moving a localized resonant region along a curved trajectory in space such that the excitation itself is spatially selective and temporally sequential. In STEREO, the gradients are modulated to produce a “spatial rapid passage”. By producing a sweeping 3D-selective excitation in time, temporal adjustments to the pulse can be made to compensate for the spatial variation of B0 and B1 as the “resonant region” traverses through space. Simultaneous RF transmission and signal detection preserves ultrashort-T2* signals. This method of achieving spatial isolation is particularly novel in MR imaging and opens opportunities for numerous novel applications that could not be considered with standard Fourier-based techniques.

Seminário do Grupo de Óptica: “Dinâmica de transporte de fotossensibilizadores em células”

Nos últimos anos, os estudos de técnicas fotônicas não invasivas têm ganhado destaque devido à preocupação com a saúde. Nestes estudos, o uso de fotossensibilizadores na terapia fotodinâmica desempenha um papel fundamental para os avanços da área, e tem sido utilizado com sucesso em diversas aplicações, tais como a redução de contaminantes ambientais, descontaminação de alimentos e tratamento de infecções localizadas, infecções fúngicas, acnes e câncer, Apesar de tal sucesso, a dinâmica de transporte dessas substâncias fotossensíveis nos alvos a serem tratados ainda não é um processo completamente compreendido. Assim, torna-se importante estudar a dinâmica de difusão e a entrada desses fotossensibilizadores em células e bactérias. Neste projeto, pretende-se utilizar técnicas como microscopia confocal e espectroscopia de fluorescência correlacionada (FCS), de modo a compreender tal transporte em bactérias gram-positivas e gram-negativas, e buscar diferenças na dinâmica de difusão entre elas. Do mesmo modo comparativo também serão estudadas células tumorais e sadias. Espera-se com este projeto caracterizar e modelar toda dinâmica de transporte destes fotossensibilizadores em bactérias gram-positivas e gram-negativas, buscando encontrar diferenças entre os grupos de modo a possibilitar a seletividade de um único grupo de interesse para terapia fotodinâmica.

Seminário: “Ants, Genes, and Antibiotics”

The highly successful multilateral symbiosis featuring fungus-growing ants, their fungal crop, specialized pathogenic fungi (Escopvopsis spp.), chemical defense-producing bacteria (Pseudonocardia spp.) and other microbes has been a productive system both for the discovery of secondary metabolites and as an evolutionary model. The system had a single origin some 50-60 million years ago in the Amazon and has spread to over 200 species throughout Central and South America and southern states of the USA. This talk focuses on the biologically active small molecules produced by the Pseudonocardia spp. in our initial survey. These bacterial symbionts displayed remarkable molecular diversity at both the strain and higher phylogenetic levels. Using a combination of metabolomic and genomic assays along with ecologically relevant phenotypic screens for bioactivity, we have begun to understand some of the genetic mechanisms underlying this diversity. Preliminary results have illustrated, for example, how structurally closely related molecules can be produced by biosynthetic pathways clustered on the chromosome, biosynthetic pathways clustered on plasmids, and split pathways on plasmids.

Journal club: “O caminho de Louis de Broglie até a mecânica ondulatória”

O físico francês Louis de Broglie desenvolveu em 1923-1924 a primeira teoria dualística onda-partícula válida tanto para a luz quanto para corpúsculos como o elétron. Costuma-se descrever apenas a relação entre momentum e comprimento de onda como sendo a principal contribuição de De Broglie, mas ele desenvolveu uma sofisticada teoria, fundamentada tanto na relação de Planck entre energia e frequência quanto na teoria da relatividade especial, para estabelecer as propriedades ondulatórias associadas a uma entidade quântica qualquer. Também estabeleceu a relação entre probabilidade de interação e a amplitude da onda associada ao quantum (antes de Max Born), bem como as propriedades fundamentais da emissão estimulada. Este seminário apresentará o desenvolvimento das ideias de Louis de Broglie que levaram até esses resultados, discutindo também as limitações de sua teoria.

High energy physics seminars: “Singularidade Cosmológica e Mecânica Quântica”

A relatividade geral implica que o Universo começou com uma singularidade, o que, afinal, não quer dizer nada, senão que não se pode usar essa teoria até esse momento, e que portanto é necessário quantizar a gravidade. De fato, existem outras indicações semelhantes, as perturbações primordiais são entendidas hoje em dia como flutuações quânticas do vácuo. Partindo desse pressuposto, é possível explicar todos os dados que tangem o universo primordial, inclusive os recentes do Planck. Por outro lado, este regime quântico é bem diferente de todo que se pode testar no laboratório, dessa forma, o estudo dessa fase nos permite testar diferentes teorias, como as de variáveis escondidas ou nas que implicam uma equação de Schrödinger modificada não-linearmente. Com um exemplo simples, mostrarei quais são as consequências possíveis e como vinculá-la.

Para mais informações sobre o seminário, acesse http://www.ifsc.usp.br/~lattice/hepseminar/

Journal Club: “Spin-Electron-Phonon Excitation in Re-based Half-Metallic Double Perovskites”

This talk will discuss the article with the above title, by A. F. García-Flores et al, Phys. Rev. Lett. 108, 177202 (2012), with the following abstract:

A remarkable hardening ($ 30 cm 1) of the normal mode of vibration associated with the symmetric stretching of the oxygen octahedra for the Ba2FeReO6 and Sr2CrReO6 double perovskites is observed below the corresponding magnetic ordering temperatures. The very large magnitude of this effect and its absence for the antisymmetric stretching mode provide evidence against a conventional spin-phonon coupling mechanism. Our observations are consistent with a collective excitation formed by the combination of the vibrational mode with oscillations of Fe or Cr 3d and Re 5d occupations and spin magnitudes.

Seminário especial (Grupo de Óptica): “Silica-based Hybrid Nanoparticles: Novel Alternative”

Recent advances in the synthesis and characterization of functional materials on the nanometer scale have allowed their exploration for applications in many fields, including biological and biomedical areas. Emerging inorganic nanoparticles, such as carbon nanotubes, quantum dots, mesoporous silica/gold/supermagnetic nanoparticles, have been widely used in biomedical research with great optimism for cancer diagnosis and therapy. The main therapeutic applications of inorganic nanomaterials have focused on drug and gene delivery, targeted therapy, thermotherapy and photodynamic therapy. Recently, hybrid silica-based nanoparticles have attracted a great deal of attention as drug delivery systems due to their outstanding features of nontoxicity, tunable surface, high loading capacity and modifiable morphology. In this seminar, I will discuss our recent research on the development and application of hybrid silica-based nanoparticles in photodynamic therapy and drug delivery for cancer treatment.

Seminário do Grupo de Óptica: “Silica-based Hybrid Nanoparticles”

Recent advances in the synthesis and characterization of functional materials on the nanometer scale have allowed their exploration for applications in many fields, including biological and biomedical areas.

Emerging inorganic nanoparticles, such as carbon nanotubes, quantum dots, mesoporous silica/gold/supermagnetic nanoparticles, have been widely used in biomedical research with great optimism for cancer diagnosis and therapy. The main therapeutic applications of inorganic nanomaterials have focused on drug and gene delivery, targeted therapy, thermotherapy and photodynamic therapy. Recently, hybrid silica-based nanoparticles have attracted a great deal of attention as drug delivery systems due to their outstanding features of nontoxicity, tunable surface, high loading capacity and modifiable morphology.

In this seminar, I will discuss our recent research on the development and application of hybrid silica-based nanoparticles in photodynamic therapy and drug delivery for cancer treatment.

Biography

Dr. Vivero-Escoto is Assistant Professor of Chemistry at the University of North Carolina Charlotte. He received his B.S. and M.S. in Chemical Engineering from the National Polytechnic Institute of Mexico and a Ph.D. in Chemistry at Iowa State University. He was a Carolina postdoctoral fellow at UNC Chapel Hill from 2010-2012.

Dr. Vivero-Escoto received the 2013 Ralph E. Powe Junior Faculty Enhancement Award from Oak Ridge Associate Universities (ORAU) and Wells Fargo Faculty Excellence Award. He serves on the Editorial Board of the Journal of Biotechnology and Biomaterials and the Journal of Solid Tumors.

Dr. Vivero-Escoto has authored more than 25 peerreviewed journal articles, reviews, and book chapters. He is the Guest Editor of the book entitled: Silica Nanoparticles: Preparation, Properties and Uses. Nova Science Publishers Inc. (2011).

Café com física: “Limites de Validade de equações Cinéticas”

Uma abordagem comum para a dedução de equações cinéticas consiste em partir da hierarquia BBGKY (Born-Bogolyubov-Green-Kirkwood-Yvon) para as distribuições de probabilidade reduzidas de um sistema de N partículas, e utilizar a expansão em aglomerados de Meyer, em conjunto com suposições sobre a forma do potencial. Para um campo fraco obtemos a equação de Landau e no limite de fluido a equação de Balescu-Lenard. Algumas hipóteses adicionais são usualmente utilizadas, como a propriedade Markoviana do sistema. Neste seminário mostraremos porque esta é uma propriedade importante e como ela é violado se o número N de partículas não for grande o suficiente, explicando comportamentos anômalos descritos na literatura recente para alguns sistemas modêlo. Discutimos também a existência de um limiar universal em função da dimensãp espacial para a relaxação de sistemas em rede como uma quebra da validade da rota usual de dedução da equação cinética pertinente.

High energy physics seminars: “The Higgs discovery and the effective theory of the Standard Model”

The discovery of the Higgs boson at the LHC in 2012 was the main achievement of particle physics in recent years. Since then, particle physicists have been trying to understand in detail the properties of the new state: its mass, quantum numbers and how it interacts with the other known particles. An important tool in this program is the Standard Model Effective Field Theory (SMEFT). I will discuss the discovery of the Higgs boson, motivate the SMEFT and discuss its role in the search for Beyond Standard Model physics. Finally, I will present the construction of new angular observables in decays of the Higgs to four leptons in the context of the SMEFT.

Informações sobre os próximos seminários disponíveis em http://www.ifsc.usp.br/~lattice/hepseminar/

High energy physics seminars: “Indications of a non-trivial vacuum”

Using lattice field theory techniques, we investigate the vacuum structure of the field theory corresponding to perfect fluid dynamics in the Lagrangian prescription. We find intriguing, but inconclusive evidence, that the vacuum of such a theory is non-trivial, casting doubts on whether the gradient expansion can provide a good effective field theory for this type of system. The non-trivial vacuum looks like a “turbulent” state where some of the entropy is carried by macroscopic degrees of freedom. We describe further steps to strengthen or falsify this evidence.

Informações sobre os próximos seminários disponível em

http://www.ifsc.usp.br/~lattice/hepseminar/