Joint Seminar on Quantum Information and Technologies
2012/2013 | 2013/2014 | 2014/2015 | 2015/2016 | 2016/2017 | 2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | Seminar YouTube channel
until 2023/2024 Quantum Information Seminar
2018-03-22 (Thursday)
room 1.03, Pasteura 5 at 11:15 
Andrzej Dragan (IFT UW)Why the Unruh effect for massive fields won’t be observed
2018-03-15 (Thursday)
room 1.03, Pasteura 5 at 11:15
Dimitris Moustos (University of Patras)Unruh-DeWitt detectors as open quantum systems
Unruh effect is usually demonstrated by means of an Unruh-DeWitt detector, which is a point-like quantum system interacting with a quantum field and moving along a path in Minkowski spacetime. The response of a uniformly accelerated Unruh-DeWitt detector is evaluated to leading order in perturbation theory and the detector's excitation rate is found to obey a Planck distribution at the Unruh temperature.We argue that the above treatment has a restricted domain of applicability and we propose that Unruh-DeWitt detectors should be considered as open quantum systems. We calculate the evolution of the detector's reduced density matrix invoking neither the Markov nor the Rotating Wave approximation. Our analysis suggests that the relation between acceleration and temperature is best expressed in terms of the asymptotic state of the detector.
2018-03-08 (Thursday)
room 1.03, Pasteura 5 at 11:15
Jan Krzywda (IFPAN)Violation of Bell inequalities activated by decoherence
The decoherence, understood as an act of losing definite phasebetween system’s eigenstates is expected to diminish any initially presentquantum correlations. This includes the notion of non-locality, which hasbeen a central point of EPR paradox. Contrary to the common belief, weshow how at the early stage of evolution, the decoherence may activate theviolation of Bell inequality. In order to prove it, we propose the schemein which two qubits in an entangled state interact with a source ofclassical noise, while being subjected to dynamical decoupling modulatingthe influence of that noise on them. This leads to an environmentallyinduced test of non-locality, which yields a positive result only ifdecoherence is present.
2018-03-01 (Thursday)
room 1.03, Pasteura 5 at 11:15
Felix Huber (University of Siegen)New approaches to the quantum marginal problem
2018-01-25 (Thursday)
room 1.03, Pasteura 5 at 11:15
Anirudh Reddy (Raman Research Institute, Bangalore, India)Coarse Quantum Measurement: An analysis of the Stern–Gerlach experiment
2018-01-18 (Thursday)
room 1.03, Pasteura 5 at 11:15
Łukasz Cywiński (IFPAN)Qubits as sensors of noise: How I learned to stop worrying and love the decoherence
2018-01-11 (Thursday)
room 1.03, Pasteura 5 at 11:15
Konrad Szymański (UJ)Uncertainty relations from numerical range
The set of simultaneously attainable quantum expectation values of arbitrary k observables $F_1,\ldots,F_k$, called the numerical range, $W(F_1,…,F_k)$, can be applied to various problems in quantum theory. In this talk we establish a connection to uncertainty relations, in particular discussing the recent form of Maccone and Pati concerning the sum of variances. New results include semi-analytical bounds from below for the sum of variances with an error estimate and tight, analytical bounds for low-dimensional cases. Talk based on arXiv preprint 1707.03464.
2017-12-21 (Thursday)
room 1.03, Pasteura 5 at 11:15
Jan Kolodyński (ICFO Barcelona)Signal tracking beyond the time resolution of an atomic sensor by Kalman filtering
We study causal waveform estimation (tracking) of time-varyingsignals in a paradigmatic atomic sensor, an alkali vapor monitored byFaraday rotation probing. We use Kalman filtering, which optimallytracks known linear Gaussian stochastic processes, to estimatestochastic input signals that we generate by optical pumping.Comparing the known input to the estimates, we confirm the accuracy ofthe atomic statistical model and the reliability of the Kalman filter,allowing recovery of waveform details far briefer than the sensor'sintrinsic time resolution. With proper filter choice, we obtainsimilar benefits when tracking partially-known and non-Gaussian signalprocesses, as are found in most practical sensing applications. Themethod evades the trade-off between sensitivity and time resolution incoherent sensing.
2017-12-14 (Thursday)
room 1.03, Pasteura 5 at 11:15
Michał Horodecki (Uniwersytet Gdański)Fidelity in port based teleportation from irreducible representations of walled Brauer algebra
2017-12-07 (Thursday)
room 1.03, Pasteura 5 at 11:15
Remigiusz Augusiak (CFT PAN)