Theoretical models and quantum information processing protocols for molecular qubits (new topic) This research is part of the NQSTI NRRP project for the development of platforms for quantum sciences and technologies and it focuses in particular of the theoretical modelling of systems based on molecular spins. For instance, these quantum systems with many accessible levels can encode qudits, providing additional resources for quantum information processing. Molecular qudits/qubits can also be coupled to superconductive resonators for the read-out of the information [1]. The research line of the present PhD position will focus both on the modelling of these systems and of their coherent and incoherent dynamics and on the development of protocols to exploit qudits for quantum algorithms, for quantum error correction [2] and quantum sensing. The obtained results will contribute to the achievement of the milestones of Spoke 2.References[1] S. Carretta, D. Zueco, A. Chiesa, A. Gomez-Leon, F. Luis, Appl. Phys. Lett. 118, 240501 (2021).[2] A. Chiesa, F. Petiziol, M. Chizzini, P. Santini, S. Carretta, J. Phys. Chem. Lett. 13, 6468 (2022).Contact: Prof. Stefano Carretta, Email: stefano.carretta@unipr.it Non-perturbative studies of the QCD phase diagramA detailed knowledge of the QCD phase diagram is a key research goal in our studies of fundamental interactions and particle physics. Its conjectured structure contains the relevant pieces of information which are needed to understand a variety of phenomena, from matter as it would have existed in the very first instants of the Universe’s life (which are e.g. probed in heavy ion collisions) to matter as it exists in ultra-dense states relevant for cosmology (like e.g. neutron stars). A genuinely non-perturbative treatment being needed, the lattice would be supposed to give a relevant contribution. Unfortunately, we lack a positive measure in the functional integral and thus we cannot perform Monte Carlo simulations (the so-called sign problem). In collaborations with colleagues in Bielefeld we have in recent years introduced a new method to circumvent it: we compute Taylor expansions of observables at imaginary values of the baryonic chemical potential and we obtain rational approximations by multi-point Padé. Looking at the singularities of the rational functions, we obtain information on the Lie Yang singularities structure of the phase diagram. The PhD project aims at further developments and applications of the method.ReferencesP. Dimopoulos, L. Dini, F. Di Renzo, J. Goswami, G. Nicotra, C. Schmidt, S. Singh, K. Zambello, F. Ziesché, Contribution to understanding the phase structure of strong interaction matter: Lee-Yang edge singularities from lattice QCD, Phys.Rev. D105 (2022) no.3, 034513. (doi: 10.1103/PhysRevD.105.034513)Contact: Prof. Francesco Di Renzo, Email: francesco.direnzo@unipr.it Spin selectivity in chiral molecules and its applications to quantum technologiesWe are at the dawn of the second Quantum Revolution which will impact many aspects of our life. Molecular spin qudits are promising for quantum technologies [1], however their weak interaction with magnetic fields forces to work at very low temperatures and limits the possibility of reading quantum information stored into single molecules. A solution could be found by combining two basic ingredients of nature, Spins and Chirality, in the Chiral-Induced Spin Selectivity (CISS) phenomenon. In particular, electron transport through chiral objects selects a particular spin orientation depending on the helicity of the chiral bridge and this filtering occurs with high-efficiency even at room temperature. We have recently shown that CISS in a molecular setup could be exploited to initialize, process and readout quantum information even at relatively high temperatures [2]. CISS is not currently understood and the aim of this research is to develop theoretical models to investigate CISS in electron transfer, simulate experimental results and design quantum applications based on CISS. Different theoretical tools ranging from DFT to master equations will be exploited. This research is within the European ERC Synergy project CASTLE.References[1] S. Carretta, D. Zueco, A. Chiesa, A. Gomez-Leon, F. Luis, Appl. Phys. Lett. 118, 240501 (2021).[2] A. Chiesa, A. Privitera, E. Macaluso, M. Mannini, R. Bittl, R. Naaman, M. R. Wasielewski, R. Sessoli, S. Carretta, Adv. Mater. 2300472 (2023).Contact: Prof. Stefano Carretta, Email: stefano.carretta@unipr.it Prof. Alessandro Chiesa, Email: alessandro.chiesa@unipr.it Laser induced graphene for sensing and energy applicationsThe discovery of graphene, the first two-dimensional carbon-based nanomaterial with exceptional mechanical, electronic and thermal properties, has stimulated strong scientific research in the last twenty years. Recently, the possibility of producing graphene on a large scale and at low cost through the laser writing of suitable precursors (Laser Induced Graphene, LIG) has opened up to innovative academic and industrial applications, especially in the area of energy conversion, storage and sensors [1]. Through this approach, graphene-based devices, such as microsupercapacitors, membranes, biosensors, etc. can be directly written on a biocompatible substrate, thus being practically ready to use [2].The candidate will deal with the synthesis and characterization of new LIG based devices, starting from different substrates of organic origin, also conveniently functionalized with metal nanoparticles, for the production of sensors (electrochemical sensors and MEMS) and electrodes for innovative energy storage systems with a very low environmental impact (sodium ion batteries and supercapacitors).References[1] R. Ye, D. K. James, J. M. Tour, Adv. Mater. 31, 1803621 (2019).[2] L. Fornasini, S. Scaravonati, G. Magnani, A. Morenghi, M. Sidoli, D. Bersani, G. Bertoni, L. Aversa, R. Verucchi, M. Riccò, P. P. Lottici, D. Pontiroli, Carbon 176, 296 (2021).Contact: Prof. Daniele Pontiroli, Email: daniele.pontiroli@unipr.it Prof. Mauro Riccò, Email: mauro.ricco@unipr.it Optoelectronic measurements to characterize and improve materials for photovoltaic applicationsThin film solar cells based on materials composed of Earth-abundant elements, received much attention in the last years. In particular, the European Union strongly encourages research project finalized to discover novel materials satisfying those requirements. At ThiFiLab we currently study Sb2Se3 and FeS2 as photovoltaic absorber. Other materials such as CuSb(S,Se)2 or hybrid organic-inorganic solar cells will be introduced in the near future. The research on such materials is challenging as they present structural defects hindering the power conversion efficiency (PCE). To improve their PCE, a deeper understanding of the relation between growth parameters and quality of the film is needed. Especially the number and nature of defects needs to be disclosed. The research will be focused on measuring the produced devices with optoelectronic techniques such as time of flight (ToF) and charge extraction by linearly increasing voltage (CELIV) for mobility determination. Moreover, transient photovoltage (TPV), time and wavelength resolved photoluminescence (PL) will provide charge lifetime measurements. The results will be used to understand how to grow films for solar cells with higher PCEs.Contact: Dr. Donato Spoltore, Email: donato.spoltore@unipr.it Prof. Alessio Bosio, Email: alessio.bosio@unipr.it Emulsions and foams for space explorationThis thesis bases on experiments ongoing on the International Space Station, using the ESA facility Soft Matter Dynamics [1] to investigate emulsions in microgravity by Diffusing Wave Spectroscopy (DWS) [2,3]. This is the first time that such an investigation is undertaken: weight-less conditions allow to investigate the intrinsic drop dynamics, and the processes influencing emulsions stability: drop aggregation, coalescence, and the collective relative motions that may result. All these are normally convoluted, and their investigation obscured, by the predominant gravity-induced dynamics and crowding. The results obtained in this Project will contribute to develop enabling technologies for future space exploration, as efficient filters based on solidified foams and emulsions.References[1] P. Born L. Cristofolini et al., Review of Scientific Instruments, 2021, 92, 124503.[2] V. Lorusso et al., Advances in Colloid and Interface Science, 2021, 288, 102341.[3] D.A. Weitz et al., Dynamic Light Scattering: Method Some Appl., Clarendon Press, 1993.Contact: Prof. Luigi Cristofolini: luigi.cristofolini@unipr.it Dr. Libero Liggieri: libero.liggieri@ge.icmate.cnr.it Large deviations and Big Jump effects in stochastic processesUnderstanding the mechanisms that trigger large fluctuations is of utmost importance for the study of rare events in stochastic processes, in many fields of research. The mechanism that typically generates them is of two types: the rare event can be produced by an accumulation of many small deviations all in the same direction, as in the case of processes with exponential tails, or by a single very large event, which makes the main contribution to the process. This occurs when "fat-tailed" distributions are present in the process, and is called the Big Jump effect. In this project we propose to study Big Jump effects in "jump processes" and continuous stochastic processes, which describe generalized transport problems. In particular, First Passage problems in restricted geometries and in the case of continuous processes will be addressed, where a formulation in terms of solitonic effects is known that has not yet been related to Big Jump effects.ReferencesSingle big jump principle in physical modelling, A. Vezzani, E. Barkai, R. Burioni, Phys. Rev. E 100, 012108 (2019)E Aghion, DA Kessler, E Barkai, Large fluctuations for spatial diffusion of cold atoms, Physical Review Letters 118 (26), 260601Contact: Prof. Raffaella Burioni, Email: raffaella.burioni@unipr.it Effect of sparsification methods of complex networks on their robustnessNetwork sparsification methods aim to reduce the number of links while minimizing the impact on the network structure [1,2,3]. One of the most used methods is the removal of links below (or above) a certain weight thresholding WT [1,3,4]. In this research, we will investigate how sparsification methods affect the robustness of real complex networks. After applying WT to different threshold values, the robustness of the sparsified network to the removal of nodes and links will be analyzed [2]. The removal of nodes and links will be both random (random removal) and targeted (attack) [5]. Targeted attack strategies will remove nodes and links in decreasing order of centrality. The centrality of nodes and links will be measured both with different indicators from the literature (degree, closeness, betweenness, etc), and with new ones proposed in the context of this research.References[1] X. Yan, L. G. S. Jeub, A. Flammini, F. Radicchi, and S. Fortunato, Weight thresholding on complex networks, Phys. Rev. E 98, 042304 (2018).[2] Bellingeri, M., Bevacqua, D., Scotognella, F. et al. The heterogeneity in link weights may decrease the robustness of real-world complex weighted networks. Sci Rep 9, 10692 (2019).Contact: Prof. Davide Cassi, Email: davide.cassi@unipr.it Dr. Michele Bellingeri, Email: michele.bellingeri@unipr.it Development of a model for RNA foldingOut of all the folding problems (search for the native configuration of structures such as proteins or nucleic acids), RNA folding has long been thought of as the one for which we are the closest to a solution. As a matter of fact, structural elements known as pseudoknots (which give rise to non-trivial topologies) still pose an unsolved problem. In recent years, a theoretically simple model of free energy for RNA has been developed by us, along with a numerical computation model aimed at its minimization. All this combines conceptual and computational tools originating from theoretical physics and techniques such as Monte Carlo simulations and artificial intelligence. The aim of the PhD project is to complete the necessary steps for the method to be fully implemented in a numerical package that can be applied to realistic structures. An interested reader can have a look at the paper pointed out a few lines below. While this is NOT our model, it can provide an idea of why and how theoretical physics could be any useful for this kind of research.ReferencesBon M, Vernizzi G, Orland H, Zee A. Topological classification of RNA structures. J Mol Biol. 2008 Jun 13;379(4):900-11. (doi: 10.1016/j.jmb.2008.04.033)Contact: Prof. Francesco Di Renzo, Email: francesco.direnzo@unipr.it A molecular platform for intracellular nitric oxide sensingNitric oxide (NO) exerts multiple biological functions, including host defense against pathogens, including viruses, bacteria, and fungi. Following NO concentration fluctuations in real time at the single cell level is a challenging task due to its low concentration and short half-life. This project aims to explore fluorescent proteins (FPs) as simple NO sensors to obtain a molecular platform of genetically encoded sensors (GES) suitable for in vivo fluorescence imaging. The variants will be engineered through rational design, recombinantly expressed, and their performance as NO sensors verified spectroscopically. The performance in cellular environment will be tested with fluorescence microscopy experiments on transfected cells. The activities will be conducted in collaboration with Dr. Thomas Gensch (FZJülich, Germany).References[1] C. Montali et al., Antioxidants 11, 2229 (2022).[2] E. Eroglu, et al., Free Radic. Biol. Med. 128, 50 (2018)Contact: Cristiano Viappiani, Email: cristiano.viappiani@unipr.it Stefania Abbruzzetti, Email: stefania.abbruzzetti@unipr.it Nonlinear dynamics and structure formation in quantum systems: from the laboratory to the universeNonlinear dynamics are the basis of many interesting phenomena in physics. Self-gravitating cold dark matter, ultracold quantum gases, and hydrodynamic problems, for instance, are all described by a nonlinear Schrödinger equation in some limit. In this project we compare the evolution of two exemplary equations, the Gross-Pitaevskii equation with short-range and the Poisson-Schrödinger equation with long-range interactions [1,2]. We study, in particular, the temporal evolution in 2D models allowing e.g. for the formation of vortex structures. Such models with reduced dimensionality exploiting radial or cylindrical symmetries in the full 3D problem are important for quicker data acquisition. Analytical analysis using semiclassical and statistical physics techniques are used to interpret the results of numerical computations that will be important for understanding the formation of matter structure in the universe and in possible laboratory simulations.References[1] H.-Y. Schive, T. Chiueh, T. Broadhurst, Cosmic structure as the quantum interference of a coherent dark wave, Nature Physics 10, 496 (2014)[2] T. Zimmermann, N. Schwersenz, M. Pietroni, S. Wimberger, One-Dimensional Fuzzy Dark Matter Models: Structure Growth and Asymptotic Dynamics, Phys. Rev. D 103, 083018 (2021)Contact: Sandro Wimberger, Email: sandromarcel.wimberger@unipr.it Massimo Pietroni, Email: massimo.pietroni@unipr.it
