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TAPS2018 Projects

Quantum-mechanical modelling of heavy-element compounds: elucidating the activation of the uranyl-oxo bond in gas phase

Over the last decades, theoretical approaches have been successfully used to determine molecular properties and to provide a fundamental understanding of chemical reactivity and reaction mechanisms. Specifically, theoretical methods are particularly instructive when experimental studies of thermodynamics, kinetics, complexation, and reaction mechanisms are complicated due to, for instance, toxicity, radioactivity, and instability of chemical compounds. Most importantly, a reliable quantum-mechanical treatment must address the fact that electrons do not move independently, but in a correlated fashion. However, the accurate modeling of the correlated motion of electrons remains an open problem in theoretical chemistry. This difficulty originates from the different contributions that govern the correlated motion of electrons, commonly referred to as strong and weak correlation. To treat strong electron correlation, multiconfigurational wavefunction-based methods can be applied. However, standard multi-reference methods are computationally very expensive and their computational cost scales exponentially with the size of the system, an effect known as the curse of dimension. To overcome the exponential-scaling wall of standard ab initio methods, unconventional electron correlation approaches have been introduced into quantum chemistry; most of these approaches are based on compact parameterizations of the many-electron wavefunction. In this research project, we will model strongly correlated materials using approaches based on non-interacting electron pairs, called geminals. Specifically, we will apply quantum mechanical methods that are being developed in our laboratory (Antisymmetric Product of 1 reference orbital Geminals (AP1roG) and its extensions) to model the thermochemistry of uranium-containing complexes. The focus will lie on compounds containing the uranyl cation (UO2+2) as its fundamental building block. Such complexes are immensely difficult to describe theoretically because correlation effects and relativistic effects have to be described on equal footing. Furthermore our methods will be benchmarked against conventional and unconventional electronic structure methods, such as the Complete-Active-Space Self-Consistent-Field approach or the Density Matrix Renormalization Group algorithm. This will allow us to assess the accuracy and reliability of the geminal-based methods developed in our laboratory.

Supervisor: Katharina Boguslawski (k.boguslawski[at]fizyka.umk.pl),
Time:

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Positron & Positronium Physics

Positrons (the antiparticles of electrons) and positronium (the bound state of an electron and a positron) are currently employed in the exploration of many fundamental effects ranging from the large-scale phenomena occurring in astrophysics (in interstellar media) to the interactions between single particles of ordinary matter and antimatter. The positron laboratory at the Faculty of Physic NCU is currently equipped with the Positron Annihilation Lifetime Spectrometer (PALS) to study positron/positronium behavior in liquids and solids. Moreover the slow-positron beam system is under construction to study positron scattering from single atoms and molecules in the gas-phase. In general this project will be connected with the problem of positron (anti-electron) interaction with ordinary matter. The student will have an option to choose one from the following activities : (1) characterization of positron lifetimes for selected materials (liquids or solids); this activity includes acquisition and analysis of the positron lifetime spectra along with the interpretation of results (2) participation in the work related to the formation of slow-positron beam

Supervisor: Kamil Fedus (kamil[at]fizyka.umk.pl),
Time: August

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Switchable Optical Vector Beam Microscopy in High-Resolution Biomedical Imaging

Recent advances in photonics, data acquisition and data processing has brought about a revolution in optical microscopy that now enables high-resolution visualization of biological objects at different scales of organization. The advances in optical engineering allows for the development of novel tools that can be used in the innovative optical microscopy. Optical vector beams represent non-standard optical fields, in which polarization depends also on the transverse coordinates across the beam. In this project, the student will assess the performance of the high-resolution optical microscopy with switchable vector beams, and will apply the microscopic system in the imaging of biological samples. Apart from a hands-on training in optical system design and construction, the student will have the opportunity to learn state-of- the-art methods in optical engineering, optical signal detection and data processing. Therefore, we seek a motivated and open-minded person with basic knowledge of optics and interferometry. Skills in signal processing and programming are advantageous but not necessary.

Supervisor: Ireneusz Grulkowski (igrulkowski[at]fizyka.umk.pl),
Time:

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Sunbathing around protostars


Stars form in dense molecular clouds, where gas and dust are well-shielded from the interstellar UV radiation. Nonetheless, UV photons can be produced in situ in the surroundings of young protostars: either by the accretion of material onto the disk or its partial ejection in the powerful jets. Recent observations with the Herschel Space Telescope reveal that even relatively small UV fields dramatically change the chemical composition of the gaseous envelopes. The student will have an opportunity to reduce and analyse maps of molecular emission around protostars and compare them to new, state-of-the-art models including the role of UV photons.The data was obtained by far-infrared space telescope Herschel and single-dish submillimeter telescope IRAM.

Supervisor: Agata Karska (agata.karska[at]umk.pl),
Time: mid-July / mid-August

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Trapped ions


Ion trapping is an experimental technique commonly applied in atomic and molecular spectroscopy, cold chemistry, quantum information, etc. In the FAMO lab experiment some multi-species ionic crystals, built of calcium and molecular ingredients, are investigated. Summer student will be allowed to spent their time on some of following activities: numerical simulations of molecular dynamics of ion ensemble, running the experiment, data analysis, construction of macroscopic models of ion trap.

Supervisors: Łukasz Kłosowski (lklos[at]fizyka.umk.pl),
Mariusz Piwiński (piwek[at]fizyka.umk.pl)
Time:

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Quantum information with single photons


Entanglement is a basic block of quantum communication and computation protocols. In practice, the entanglement can be produced by means of the parametric down-conversion process where one photon decays into a pair of photons. The purely quantum mechanical features of a photon pair in conjunction with novel detection techniques can be used to enhance the quantum communication protocols. The student will work on experiment and/or theory of a new quantum communication protocol based on time resolved single photon detection techniques. This will be a chance to gain experience in working with the state-of-the-art superconducting single photon detectors, single photon sources, and data acquisition and analysis systems.

Supervisor: Piotr Kolenderski (kolenderski[at]fizyka.umk.pl),
Time:

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Plasmonic interactions in hybrid nanostructures with graphene

Metal-enhanced fluorescence (MEF) occurs in hybrid structures due to the presence of localized plasmon resonance in metallic nanoparticles. In this project we apply Quantum Dots (QDs) and Silver Island Film (SIF) to construct a hybrid nanostructure with the graphene layer (SLG) as the energy acceptor. The student will be involved in some steps of the hybrid structure fabrication including synthesis of the SIF and graphene transfer. The experiment will be focused on imaging the fluorescence from QDs in presence of SIF and/or SLG using wide field fluorescence microscopy in the visible spectral range. The main aim of this experiment is to describe the energy transfer in the such hybrid nanostructures and the influence of various parameters on the efficiency of this process.

Supervisors: Dorota Kowalska (dorota[at]fizyka.umk.pl),
Sebastian Maćkowski (mackowski[at]fizyka.umk.pl)
Time: July

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Unidentified interstellar spectral features


Long time ago M.L. Heger (1922) found two reasonably broad spectral features which remained stationary in the spectrum of the spectroscopic binary HD23180. The features were seen in a few more stars as well. In 1930-ties P.W. Merrill and collaborators proved their interstellar origin. Since that time a couple of hundred such features, known as diffuse interstellar bands (their profiles are broader than those of interstellar atomic lines), have been discovered. However, their carriers remain unidentified despite numerous efforts. The project would try to find, among the many diffuse bands, a few which may share the same carrier. There are already some suspects but a definite conclusion requires an analysis of many spectra. We have an extensive database of high resolution, echelle spectra. They are to be used for measuring intensities of several diffuse bands being likely of the same origin and to build their high signal-to-noise profiles which are most likely characteristic to given species. For this task our database should be applied together with the code allowing all necessary measurements and visualizations. This code, called Dech, is to be downloaded from the site “gazinur.com” and installed. The use of it is very straightforward. The task should be completed with a draft of a research paper to be published later.

Supervisor: Jacek Krełowski (jacek[at]umk.pl),
Time:

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Eye movement data analysis

Our aim is to develop the libraries for automatic analysis of human eye movement acquired by eyetrackers of high and low quality. Main eye movement events are: fixations, saccades, smooth pursuits and blinks. Determining them allows one to characterize the subject’s cognitive processes during looking at the stimulus. It is partially ready, but must be improved and tested. Additionally the interactive graphical user interface must be prepared. Next step is to adapt the algorithms for chimpanzees.

Supervisor: Jacek Matulewski (jacek[at]fizyka.umk.pl),
Time:

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Bioimaging with plasmonic nanoparticles

Optical properties of noble metals, such as gold and silver, change tremendously when their physical dimensions are shrank to nanometer scale. Such nanoparticles (NPs) can scatter or absorb light very efficiently, at specific wavelengths from visible and near infrared spectrum, due to the resonant interaction between the electrons confined in the nanoparticle and the incident light – the phenomenon known as localized surface plasmon resonance (LSPR). Plasmonic nanoparticles find numerous physical and biological applications, for example, bioimaging where they provide a photostable alternative for fluorescent dyes. In this project we develop an interferometric optical setup for ultrasensitive 3D detection of plasmonic nanoparticles used for bioimaging and biosensing. The student will participate in development and testing of the advanced optical setup getting familiarity with optical equipment (i.e. femtosecond laser, optical parametric oscillator, fast spectrometers) and experimental techniques (i.e. optical coherence microscopy).

Supervisor: Seweryn Morawiec (seweryn.morawiec[at]fizyka.umk.pl),
Time:

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Plasmonic optoelectronics


Optically active components based on metallic nanostructures are considered to be a promising alternative to typical optoelectronic circuits. Instead of silica waveguides, light can be transported through silver nanowires by polaritons – quasiparticles arising from the coupling between photons and oscillations of free electrons. Carefully selected long silver nanowires, locally decorated with nanocrystals, can operate as plasmonic modulators or amplifiers, suitable for processing information in such miniaturized optoelectronic devices. The student will be involved in ongoing research concerning interactions between propagating polaritons and nearby nanocrystals. Innovative and very unique experiments will be performed using a custom-made two-objective fluorescence microscope, which enables to observe non-local, polariton-mediated processes. Among specific effects we intend to focus on methods and techniques of generation and controlled propagation of plasmonic excitations, networks attenuation, sensitivity to polarization, polariton stimulated emission etc.

Supervisors: Dawid Piątkowski (dapi[at]fizyka.umk.pl),
Sebastian Maćkowski (mackowski[at]fizyka.umk.pl)
Time: August

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Investigation of thermal stability of Nitrile Hydratase enzyme using molecular dynamics simulation


Nitrile hydratase (NHase) is a key enzyme in hydration of nitriles to their corresponding amides, and it is commonly composed of – and -subunits and contains either a non-heme iron (Fe-NHase) or non-corrin cobalt (Co-NHase). However, most NHases with relatively high activity have the problem of poor thermostability. This defect becomes a bottleneck for industrial application of NHases. It is widely known that nitrile-hydration is an exothermic reaction. In order to prevent NHase from inactivation under such circumstance, obtaining a NHase with high thermostability becomes extremely essential. During this project using theoretical physics approach – classical (newtonian) molecular dynamics simulations – the student will check thermostability of Co-NHase (pdb code 1IRE). Running simulations in a few temperature regimes will give answer when the enzyme is losing catalytic activity because of protein’s denaturation. Theoretically obtained results will be compared to experimental data.

Supervisor: Łukasz Pepłowski (drpepe[at]fizyka.umk.pl),
Time: July

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Non-markovian open quantum systems with memory kernel

Considering quantum dynamics, Hamiltonian dynamics is an idealisation for closed systems, and a proper description in a typical situation is an open dynamics, obtained by tracing out the environmental degrees of freedom. Usually Born and Markov approximation are assumed, but it fails when one consider short-time scales – then we may observe an exchange of information between the system and the environment, building correlations and information backflow. These phenomena are known as quantum non-markovianity and are investigated in our group. The student will be introduced to the theory and involved in the research in the field.

Supervisors: Gniewomir Sarbicki (gniewko[at]fizyka.umk.pl),
Dariusz Chruściński (darch[at]fizyka.umk.pl)
Time: August

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New positive maps for detecting entanglement

The hard task in the quantum information and computation field is to determine whether a given state is entangled or not. The problem is in one-to-one correspondence with the problem of classification of positive maps, which in turn are related to special observables on the composed system – entanglement witnesses, which checks the entanglement of a given state in a similar way the Bell inequalities do. We are looking for new classes of positive maps and test various hypothesis numerically. We are as well interested in the geometrical properties of the considered sets. The student will be introduced to the field and will choose his/her activity out of a wide range – from pure operator theory and geometry via quantum information to numerical problems.

Supervisors: Gniewomir Sarbicki (gniewko[at]fizyka.umk.pl),
Dariusz Chruściński (darch[at]fizyka.umk.pl)
Time: August

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Graphene plasmonics for nanoscaled light-matter interactions

Plasmonic nanostructures, typically made of noble metals, show a remarkable ability to concentrate light in subwavelength domains of space. This can be used to spatially and spectrally tailor electromagnetic field distributions in nanoscopic domains, and results in a plethora of applications in medicine, for solar energy harnessing, for novel materials of previously inaccessible optical properties, etc. A major bottleneck of traditional plasmonics is, however, a lack of tunability: once fabricated, a gold or silver nanostructure can hardly be modified. This can be circumvented with tunable materials, such as graphene. The goal of this project is to investigate the potential to modify the optical properties of graphene-based plasmonic nanostructures. We expect basic knowledge on electrodynamics and quantum mechanics, fluent English and high motivation. Possible activities proposed for summer students may focus on analytical or numerical investigations, depending on the student’s individual skills and expectations.

Supervisor: Karolina Słowik (karolina[at]fizyka.umk.pl),
Time: mid-July / August

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Light interactions to asymmetric quantum systems

When a quantum system, such as an atom, a molecule or a quantum dot, is subject to illumination with a resonant light beam, it undergoes so-called Rabi oscillations: periodic population transfer between the ground and the excited states. This leads to an interesting effect if an the quantum system is asymmetric, i.e. characterized with a ground state dipole moment. In Rabi oscillations, the mean dipole moment is periodically modified, leading to potentially attractive applications such as highly tunable light sources. The aim of the project is to theoretically study quantum dynamics of specific real asymmetric systems in feasible experimental conditions, taking into account decoherence effects and losses. From the candidates we expect basic knowledge on quantum mechanics, fluent English and high motivation.

Supervisor: Karolina Słowik (karolina[at]fizyka.umk.pl),
Time: mid-July / August

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Towards Orbital-Free Density Functional Theory

The Orbital-Free Density Functional Theory (OF-DFT ) is the powerful tool to investigate the properties of many-electron systems. In principle, the OF-DFT method scales linearly with the systems size allowing to perform simulations of large, complicated molecules, clusters, and almost all extended systems. Since the beginning of OF-DFT, the theory struggles with the lack of properly defined and accurate density-dependent kinetic energy (KE) functional and potentials which plays a crucial role in the solution of DFT Euler equation laying behind this theory. In general, the KE term may be decomposed into the von Weizsäcker part and so-called Pauli term including non-local effects. In case of former, the exact analytical form expressed in terms of electron density is known for many years. The unambiguous, density-dependent form of later still remains unknown. The Pauli term, however, can be expressed through Kohn-Sham orbitals and thus might be analyzed using some more advanced methods such as optimized effective potential (OEP) method. The student will be involved in the generation of exact kinetic energy potentials for different atoms and molecules, using the OEP method and software developed in our group. She/He will also help in the analysis of the results which will (hopefully 🙂 ) lead to the derivation of accurate, density-dependent (semi)local approximations of KE potentials and functionals. Potential candidates should have basic knowledge of quantum chemistry and be familiar with Linux operating system.

Supervisor: Szymon Śmiga (szsmiga[at]fizyka.umk.pl),
Time: July

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Fast and accurate quantum chemistry

In the realm of quantum chemistry two main group of methods have been developed, namely the wave function theory (WFT) and density functional theory (DFT). The latter method has become very popular, especially in the pharmaceutical industry calculations, due to its very low computational cost which allows applying DFT to very big molecular systems. The former, although more computationally expensive, allows to obtain much more reliable results than those from DFT, however, the applicability of those methods is rather limited to small systems such as atoms, diatomic, and small molecules. The DFT is an exact theory in principle, but in practice, the final quality of the results strongly depends on approximations of the exchange-correlation (XC) used in the Kohn-Sham (KS-DFT) calculations. In general, those functionals are constructed empirically using electron density, its gradient, and Laplacian, embedding in the analytical functional form some theoretical constraints. This kind of functionals leads to rather moderate results. In order to improve the quality of the prediction, we need to include a more sophisticated ingredient such as KS orbitals (e.g. in meta-GGA, hybrid functionals) and orbitals energies (e.g. in double hybrid functionals). In our group we have developed the family of orbital-dependent, spin-component-scaled second-order correlation functionals (OEP2-SCS) based on well know from WFT, spin-resolved Møller–Plesset second-order correlation energy expression. This functional combines lack of empiricism from WFT and low computational demands from DFT. In the summer project, we will benchmark our OEP2-SCS functionals against some well-known data sets (reaction energies, atomization energies, etc. ), both for closed- and open-shell systems. The student will be involved in some coding, thus the knowledge of some programing language (e.g. python, C, Fortran, …) will be appreciated. Potential candidates should also have some basic knowledge of quantum chemistry and be familiar with Linux operating system.

Supervisor: Szymon Śmiga (szsmiga[at]fizyka.umk.pl),
Time: July

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The CASTLE


Cold Atomic Space-Time Laboratory apply ultra-cold matter and optical clocks experiments to explore new physics and cosmology. We measured the best constraints on finite-structure constant transient variations due to the coupling with possible topological defects survived from the cosmological phase transitions at early Universe. We are currently looking for students to participate in both improving out experimental systems and analysing the data we acquired. These tasks require basic knowledge of cosmology or the atomic and molecular physics, and experimental skills. More information is available at Cold Atomic Space-Time Laboratory.

Supervisor: Michał Zawada (zawada[at]fizyka.umk.pl),
Time:

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