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Prof. Tamás Kiss (Wigner Research Centre for Physics, Budapest, Hungary)23/05/2022, 09:30Talk
Nonlinear evolution is not a usual phenomenon in quantum physics. It is possible to define a time-evolution for an ensemble of equally prepared systems in a somewhat unusual way: take N systems, apply an entangling unitary transformation, measure all but one of the systems and, depending on the measurement results, keep or throw away the remaining system. This procedure applied to the whole...
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Prof. Horia Cornean (University in Aalborg, Denmark)23/05/2022, 11:00Talk
By extending the gauge covariant magnetic perturbation theory to operators defined on half planes, we prove that for general 2d random ergodic magnetic Schrödinger operators the celebrated bulk-edge correspondence is just a particular case of a much more general paradigm, which also includes the theory of diamagnetic currents and of Landau diamagnetism. Our main result is encapsulated in a...
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Prof. Saverio Pascazio (University of Bari, Italy and INFN Italy)23/05/2022, 14:00Talk
We derive and discuss one- and two-dimensional models for classical electromagnetism by making use of Hadamard’s method of descent. Low-dimensional electromagnetism is conceived as a specialization of the higher dimensional one, in which the fields are uniform along the additional spatial directions. We then consider two-dimensional models for a charged spin-1/2 particle, both in the free case...
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Prof. Alain Joye (Université Grenoble Alpes, Grenoble)23/05/2022, 15:30Talk
We consider a discrete-time non-Hamiltonian dynamics of a quantum system consisting of a finite sample locally coupled to several infinite reservoirs of fermions with a translation symmetry. In this setup, we compute the asymptotic state, fluxes of fermions into the different reservoirs, as well as the entropy production rate of the dynamics.
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This is joint work with S. Andréys and R. Raquépas. -
Paolo Facchi (University of Bari, Italy and INFN Italy)24/05/2022, 09:30Talk
We show that for any finite-dimensional quantum systems the conserved quantities can be characterized by their robustness to small perturbations: for fragile symmetries, small perturbations can lead to large deviations over long times, while for robust symmetries, their expectation values remain close to their initial values for all times. This is in analogy with the celebrated...
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Prof. Konstantin Pankrashkin (Universität Oldenburg, Oldenburg)24/05/2022, 11:00Talk
We discuss the construction of the trace operator defined on Sobolev spaces over a class of infinite trees based on an identification of the abstract boundary with an Euclidean domain. This can be used to study coupling problems between objects of different dimensions. Joint work with Kiyan Naderi (Oldenburg).
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Prof. Gernot Alber (Technische Universität Darmstadt)24/05/2022, 14:00Talk
Coherent laser-induced excitation processes based on timescale hierarchies offer interesting perspectives for the controlled and deterministic preparation of entangled multipartite quantum states. Greenberger-Horne-Zeilinger (GHZ) and W-states are prominent examples of such multipartite quantum states which constitute valuable resources for quantum information processing. Motivated by current...
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Prof. Gregory Berkolaiko (Texas A&M University, College Station, TX.)24/05/2022, 15:30Talk
The question of optimizing an eigenvalue of a family of self-adjoint operators that depends on a set of parameters arises in diverse areas of mathematical physics. Among the particular motivations for this talk are the Floquet-Bloch decomposition of the Schroedinger operator on a periodic structure, nodal count statistics of eigenfunctions of quantum graphs, conical points in potential energy...
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Prof. Uzy Smilansky (Weizmann Institute of Science, Rehovot)25/05/2022, 09:30Talk
The question asked in the title is addressed from two points of view:
First, we show that providing enough (term to be explained) spectral data, suffices to reconstruct uniquely generic (term to be explained) matrices. The method is well defined but requires somewhat cumbersome computations.
Second, restricting the attention to banded matrices with band-width much smaller than the...
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Prof. Stephen M. Barnett (School of Physics and Astronomy, University of Glasgow)25/05/2022, 11:00Talk
Time in quantum mechanics, especially the non-relativistic theory has privileged position in that
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unlike the Cartesian coordinates it is a parameter rather than an operator. Moreover, it is a parameter
over which we have no control: time passes and our quantum systems evolve. Yet the theory is
essentially time-symmetric (as is most of the rest of physics) so there is a sense in which... -
Prof. Rafael Benguria (Pontificia Universidad Católica de Chile )25/05/2022, 14:00Talk
In this talk I will present some new results on the excess charge for bosonic systems.
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25/05/2022, 15:30Poster
Quantum computing has received a lot of attention recently, and specifically its application in quantum chemistry looks very promising. This research project summarizes the most important methods used in calculating the electronic structure of a chemical system on quantum computers. This includes the formulation of the problem in first and second quantization and the use of classical...
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25/05/2022, 15:30Poster
The work concerns asymptotic synchronization and phase-locking in qubit networks undergoing Markovian evolution described by the GKSL master equation with normal Lindblad operators. For a two-qubit system, all synchronization and phase-locking mechanisms within the given framework are obtained and classified, using solely analytic methods. In the case of synchronization, the results are...
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25/05/2022, 15:30Poster
It is known from previous works that discrete flip-flop quantum walks with the Grover coin on finite graphs can exhibit the phenomenon of asymptotic trapping, where the walker can evade a sink introduced in the graph indefinitely with non-zero probability. This interference phenomenon is caused by so-called trapped states – eigenstates of the walk with limited support, i.e. with zero...
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25/05/2022, 15:30Poster
We present our advances on the implementation of a measurement-induced nonlinear protocol for quantum state matching using some commercially available quantum computers. Using this implementation, we present a benchmark that detects quantitatively the device specific errors. In contrast to current benchmarks trends, our circuit is a non-random deep circuit. Among the devices analyzed, we...
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25/05/2022, 15:30Poster
The localization phenomenon usually happens due to the existence of disorder in a medium. Nevertheless, specific quantum systems allow dynamical localization solely due to internal interactions. We study a discrete-time quantum walker which exhibits disorder-free localization. The quantum walker moves on a one-dimensional lattice and interacts with on-site spins by coherently rotating them...
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25/05/2022, 15:30Poster
We study the isospectrality problem for a free quantum particle confined in a ring with a junction. By characterizing the energy spectrum in terms of a spectral function, we classify all the possible self-adjoint realizations. The latter turn out to be divided in two classes, which are discerned by the action of parity.
Main reference: G. Angelone, P. Facchi and G. Marmo, *Hearing the...
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25/05/2022, 15:30Poster
Machine learning field has shown incredible impact on many kinds of optimization problems. Recently the power of machine learning was applied to speed up the quantum states preparation. Although approximation with quantum generative adversarial networks is one of the fastest ways to prepare a generic quantum state, training time for such models is still significant and can easily impair...
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25/05/2022, 15:30Poster
We consider measurement disturbance tradeoffs in quantum machine learning protocols which seek to learn about quantum data. We study the simplest example of a binary classification task, in the unsupervised regime. Specifically, we investigate how a classification of two qubits, that can each be in one of two unknown states, affects our ability to perform a subsequent classification on three...
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25/05/2022, 15:30Poster
Nonlinear squeezing is an important feature for universal quantum computing, that in principle enables universal control of a continuous variable system [1]. Simultaneously, it is a subject to current experimental effort [2,3,4]. We show its behaviour under decoherence and possibilities of protection by Gaussian operations [4]. Therefore, our results can enhance the ability to detect the...
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25/05/2022, 15:30Poster
The evolution of an open quantum system is described by a quantum channel, i.e. a completely positive trace-preserving map. Under the Markovian approximation, the continuous dynamics of an open quantum system is given by a semigroup with a Gorini-Kossakowski-Lindblad-Sudarshan (GKLS) generator. In this poster we will discuss several constraints for the number of steady and asymptotic states of...
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25/05/2022, 15:30Poster
Using quantum Fisher information (QFI), we will show that parameter estimation with a driven discrete-time quantum walk (QW) provides a better bound over the attainable precision when compared to standard QW. Here, we are studying the quantum estimation of the phase parameter of the evolution operator. With this study, we can also show that QW set-up can be used to reduce the variance in the...
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25/05/2022, 15:30Poster
In the presented poster, known results on the spectral properties of quantum graphs with preferred orientation coupling are reviewed. Special attention is paid to the recent result on magnetic ring chains with preferred orientation coupling.
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25/05/2022, 15:30Poster
The trajectory of a quantum particle during unitary evolution between its preparation and a later measurement can not be studied without measuring the particle, but measurement disturbs the state and the statistics of the measurement outcomes no longer pertain to the original evolution. We show how using path integral methods a sensible quasi-probability can be assigned to the event of passing...
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25/05/2022, 15:30Poster
We introduce the general scheme of discrete-time quantum walk algorithm for the search and state transfer algorithm based on discrete-time quantum walk. We prove that adding a loop to each vertex improves success probability of the search algorithm on a complete $M$-partite graph in the limit of a large graph. We show that the state transfer algorithm performs perfect state transfer between...
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25/05/2022, 15:30Poster
We propose and analyze a non-unitary variant of the continuous time Grover search algorithm based on frequent Zeno-type measurements. We show that the algorithm scales similarly to the pure quantum version by deriving tight analytical lower bounds on its efficiency for arbitrary database sizes and measurement parameters. We study the behavior of the algorithm subject to noise, and find that...
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25/05/2022, 15:30Poster
For $\varepsilon>0$ and $n\in\mathbb{N}$ consider the infinite cone $\Omega_{\varepsilon}:=\big\{(x_1,x')\in (0,\infty)\times\mathbb{R}^n: \, |x' | < \varepsilon x_1\big\}$ and the operator $Q_{\varepsilon}^{\alpha}$ acting as the Laplacian $u\mapsto-\Delta u$ on $\Omega_{\varepsilon}$ with the Robin boundary condition $\partial_\nu u=\alpha u$ at $\partial\Omega_\varepsilon$, where...
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Prof. Zdeněk Hradil ( Palacky University Olomouc)26/05/2022, 09:30Talk
Reaching ultimate performance of quantum technologies requires the use of detection at quantum limits and access to all resources of the underlying physical system. We establish a full quantum analogy between the pair of angular momentum and exponential angular variable, and the structure of canonically conjugate position and momentum. This includes the notion of optimal simultaneous...
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Dr Raffaele Carlone (Università “Federico II” di Napoli)26/05/2022, 11:00Talk
In the first part we will describe the dynamics of a quantum particle coupled to bosonic fields, in the quasi-classical regime. In this case, the fields are very intense and the corresponding degrees of freedom can be treated semiclassically. We prove that in such a regime the effective dynamics for the quantum particles is approximated by
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the one generated by a time-dependent point... -
Prof. János A. Bergou (Department of Physics and Astronomy, Hunter College of the City University of New York)26/05/2022, 14:00Talk
Einstein in 1905, in his explanation of the photoelectric effect, postulated that light, the quintessential wave, had to possess particle-like properties. In the course of 1923-24, de Broglie, analyzing electron scattering from metal surfaces, postulated that electrons, the quintessential particles, must possess wave-like properties. In 1928, Bohr made the first attempt to reconcile the two...
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Prof. Mário Ziman (Institute of Physics, Slovak Academy of Sciences)26/05/2022, 15:30Talk
The concept of divisibility of dynamical maps will be used to introduce an analogous concept for quantum channels by analyzing the simulability of channels by means of dynamical maps. In particular, this is addressed for Lindblad divisible, completely positive divisible and positive divisible dynamical maps. The corresponding L-divisible, CP-divisible and P-divisible subsets of channels are...
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Prof. Wolfgang P. Schleich (Institut für Quantenphysik and Center for Integrated Quantum Science and Technology (IQST), Universität Ulm)27/05/2022, 09:30Talk
The Riemann zeta function ζ plays a crucial role in number theory as well as physics. Indeed, the distribution of primes is intimately connected to the non-trivial zeros of this function. We briefly summarize the essential properties of the Riemann zeta function and then present a quantum mechanical system which when measured appropriately yields ζ. We emphasize that for the representation in...
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Prof. Leszek Sirko (Institute of Physics PAS)27/05/2022, 11:00Talk
We introduce a new spectral invariant: the generalized Euler characteristic $\mathcal{E}$ [1]. The commonly used Euler characteristic i.e., the difference between the number of vertices $|V|$ and edges $|E|$ is the most important topological characteristic of a graph. However, to describe spectral properties of differential equations with mixed Dirichlet and Neumann vertex conditions it is...
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Prof. Christine Silberhorn (Institute for Photonic Quantum Systems (PhoQS) Paderborn University)27/05/2022, 14:00Talk
Quantum technologies promise a change of paradigm for many fields of application, for example in communication systems, in high-performance computing and simulation of quantum systems, as well as in sensor technology. They can shift the boundaries of today’s systems and devices beyond classical limits and seemingly fundamental limitations.
Photonic systems, which comprise multiple optical...
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