Zapraszamy w czwartek 04.03.2021 o godz. 15:00 na seminarium.
Seminarium ONLINE pod tytułem: "Analiza danych sercowo-oddechowych metodami uczenia maszynowego" poprowadzą Urszula Czarnota i Klaudia Mielczewska.
Zapraszamy w środę 03.03.2021 o godz. 14:00 na seminarium.
Seminarium ONLINE pod tytułem: "Beyond the Quantum Switch: Quantum Circuits with Quantum Control of Causal Order" poprowadzi Hippolyte Lazourenko-Dourdent (Institut Néel / Université Grenoble Alpes)
Abstract: While the standard formulation of quantum theory relies on a fixed background causal structure, one can consider a more general framework - based on quantum theory - where the causal structure is indefinite (the "process matrix formalism"). Interestingly, the tools introduced to identify causal indefiniteness - causal non-separability and causal inequalities - have been developed by analogy with quantum entanglement and Bell inequalities. An explicit example of a physical process with indefinite causal structure is the so-called 'quantum switch'.
In this work, we take a bottom-up approach. We identify two new types of circuits that naturally generalise the fixed-order case which we fully characterise. We first introduce “quantum circuits with classical control of causal order ”, in which the order of operations is still well-defined, but not necessarily fixed in advance: it can in particular be established dynamically, in a classically-controlled manner, as the circuit is being used. We then consider “ quantum circuits with quantum control of causal order ”, in which the order of operations is controlled coherently. The latter encompasses all known examples of physically realisable processes with indefinite causal order, including the celebrated quantum switch. Interestingly, it also contains new examples arising from the combination of dynamical and coherent control of causal order, and we detail explicitly one such process. Nevertheless, we show that quantum circuits with quantum control of causal order can only generate “causal” correlations, compatible with a well-defined causal order. We furthermore extend our considerations to probabilistic circuits that produce also classical outcomes, and we demonstrate by an example how the characterisations derived in this work allow us to identify new advantages for quantum information processing tasks that could be demonstrated in practice.
Zapraszamy w czwartek 25.02.2021 o godz. 15:00 na seminarium.
Seminarium ONLINE pod tytułem: "Czego możemy dowiedzieć się z zaawansowanej analizy rytmu zatokowego w EKG o pacjentach po przeszczepie serca" poprowadzi dr n.med. Joanna Wdowczyk (GUMed) i prof. dr hab. Danuta Makowiec (UG).
Zapraszamy w czwartek 11.02.2021 o godz. 15:00 na seminarium.
Seminarium ONLINE pod tytułem: "Aerozol oddechowy i ograniczanie jego rozprzestrzeniania" poprowadzi dr hab. Jolanta Orzeł -Gryglewska (UG)
Zapraszamy w czwartek 4.02.2021 o godz. 15:00 na seminarium.
Seminarium ONLINE pod tytułem: "Zmienność rytmu i ślad węglowy" poprowadzi Teodor Buchner.
Zapraszamy w środę 27.01.2021 o godz. 14:00 na seminarium.
Seminarium ONLINE pod tytułem: "Certification of local quantum systems: Self-testing and dimension witnesses" poprowadzi Maharshi Ray (Centre for Quantum Technologies, National University of Singapore)
Abstract: We discuss schemes to certify local quantum systems via self-testing and dimension witnessing. This work leverages the graph-theoretic framework for contextuality introduced by Cabello, Severini, and Winter, combined with tools from combinatorial optimisation that guarantee the unicity of optimal solutions. We first show that the celebrated Klyachko-Can-Binicioglu-Shumovsky inequality and its generalisation to contextuality scenarios with odd cycle compatibility relations admit robust self-testing. We extend this robust self-testing result to the class of contextuality scenarios with odd anti-cycle compatibility structure which enables us to self-test arbitrary high dimensional quantum systems. Dimension witnessing is another tool for device certification where the goal is to certify the underlying dimensions of the quantum systems just from the measurement statistics. We present the concepts and tools needed for graph-theoretic quantum dimension witnessing and illustrate their use by identifying quantum dimension witnesses, including a family that can certify arbitrarily high quantum dimensions with few events.
Zapraszamy we wtorek 26.01.2021 o godz. 12:00 na seminarium.
Seminarium ONLINE pod tytułem: "Arithmetic loophole in Bell's theorem: An overlooked threat for entangled-state quantum cryptography" poprowadzi Marek Czachor (Gdańsk University of Technology)
Abstract: Bell's theorem is supposed to exclude all local hidden-variable models of quantum correlations. However, an explicit counterexample shows that a new class of local realistic models, based on generalized arithmetic and calculus, can exactly reconstruct rotationally symmetric quantum probabilities typical of two-electron singlet states. Observable probabilities are consistent with the usual arithmetic employed by macroscopic observers, but counterfactual aspects of Bell's theorem are sensitive to the choice of hidden-variable arithmetic and calculus. The model is classical in the sense of Einstein, Podolsky, Rosen, and Bell: elements of reality exist and probabilities are modeled by integrals of hidden-variable probability densities. Probability densities have a Clauser-Horne product form typical of local realistic theories. However, neither the product nor the integral nor the representation of rotations are the usual ones. The integral has all the standard properties but only with respect to the arithmetic that defines the product. Certain formal transformations of integral expressions one finds in the usual proofs à la Bell do not work, so standard Bell-type inequalities cannot be proved. The system we consider is deterministic, local-realistic, rotationally invariant, observers have free will, detectors are perfect, so is free of all the canonical loopholes discussed in the literature.
Zapraszamy w środę 20.01.2021 o godz. 14:00 na seminarium.
Seminarium ONLINE pod tytułem: "Quantum Darwinism and the spreading of classical information in non-classical theories" poprowadzi Roberto D. Baldijão (State University of Campinas, IQOQI Vienna)
Abstract: Quantum Darwinism posits that the emergence of a classical reality relies on the spreading of classical information from a quantum system to many parts of its environment. But what are the essential physical principles of quantum theory that make this mechanism possible? We address this question by formulating the simplest instance of Darwinism -- CNOT-like fan-out interactions -- in a class of probabilistic theories that contain classical and quantum theory as special cases. We determine necessary and sufficient conditions for any theory to admit such interactions. We find that every non-classical theory that admits this spreading of classical information must have both entangled states and entangled measurements. Furthermore, we show that Spekkens' toy theory admits this form of Darwinism, and so do all probabilistic theories that satisfy principles like strong symmetry, or contain a certain type of decoherence processes. Our result suggests the counterintuitive general principle that in the presence of local non-classicality, a classical world can only emerge if this non-classicality can be "amplified" to a form of entanglement.
Zapraszamy w czwartek 14.01.2021 o godz. 15:00 na seminarium.
Seminarium ONLINE pod tytułem: "Metody rekurencyjne w analizie sygnałów elektroencefalograficznych" poprowadzi dr Piotr Weber ( PG).
Zapraszamy w środę 13.01.2021 o godz. 14:00 na seminarium.
Seminarium ONLINE pod tytułem: "Semi-device-independent information processing with spatiotemporal degrees of freedom" poprowadzi Marius Krumm (IQOQI Vienna and University of Vienna)
Abstract: Nonlocality, as demonstrated by the violation of Bell inequalities, enables device-independent cryptographic tasks that do not require users to trust their apparatus. In this presentation, we consider devices whose inputs are spatiotemporal degrees of freedom, e.g. orientations or time durations. Without assuming the validity of quantum theory, we prove that the devices' statistical response must respect their input's symmetries, with profound foundational and technological implications. We exactly characterize the bipartite binary quantum correlations in terms of local symmetries, indicating a fundamental relation between spacetime and quantum theory. For Bell experiments characterized by two input angles, we show that the correlations are accounted for by a local hidden variable model if they contain enough noise, but conversely must be nonlocal if they are pure enough. This allows us to construct a "Bell witness" that certifies nonlocality with fewer measurements than possible without such spatiotemporal symmetries, suggesting a new class of semi-device-independent protocols for quantum technologies.