Środowiskowe Seminarium z Informacji i Technologii Kwantowych
2012/2013 | 2013/2014 | 2014/2015 | 2015/2016 | 2016/2017 | 2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | 2024/2025 | kanał YouTube
do roku 2023/2024 Seminarium Kwantowa Informacja | kanał YouTube
2025-05-22 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 11:15 
Michał Matuszewski (CFT PAN)Quantization of polaritons in confined structures
2025-05-15 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 11:15
Alvaro Alhambra (CSIC Madrid)Modelling quantum thermalization with quantum computers
In quantum computing and simulation, one of our main goals is to efficiently mimic natural physical phenomena in a controlled manner. The process of thermalization is one such crucial task, for which recently there has been relevant progress. In this talk, we will showcase important parts of this progress by introducing a recent dissipative evolution that models thermalization in the many-body setting, and that is efficiently implementable in a quantum computer. We then prove the following facts about this dissipative evolution:
1) It faithfully reproduces the dissipation induced by weak coupling to a bath.2) In the high temperature regime, it very quickly approaches equilibrium.3) In the low temperature regime, it can reproduce arbitrary quantum computations.
Taken together, our results show that quantum dissipative evolutions have the potential to mirror the success of classical Monte Carlo methods.
1) It faithfully reproduces the dissipation induced by weak coupling to a bath.2) In the high temperature regime, it very quickly approaches equilibrium.3) In the low temperature regime, it can reproduce arbitrary quantum computations.
Taken together, our results show that quantum dissipative evolutions have the potential to mirror the success of classical Monte Carlo methods.
2025-04-24 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 11:15
Robert Keil (University of Innsbruck, Austria)Multi-particle interference and photonic quantum interfaces
When two indistinguishable photons impinge on a beam splitter, the particles leave the device together in the same output due to the underlying two-photon interference [1]. This well-known Hong-Ou-Mandel effect is at the basis of photonic quantum information processing and various other applications. For more than two particles, the dynamics gets increasingly complex and a rich variety of interference phenomena can arise. In this talk, I will present our latest experimental results on four-photon interference obtained from spontaneous parametric down-conversion (SPDC). In particular, I will demonstrate how symmetries can affect the ability of interference [2] and how entanglement can lead to a collective four-particle interference, which is completely invisible when smaller subsets of particles are detected [3]. I will also highlight how semiconductor quantum dots can be used as a multi-photon source via active temporal-to-spatial mode demultiplexing [4]. Finally, I will introduce our new project on establishing an interface between SPDC and quantum-dot emitted photons enabled by active spectral-temporal shaping of the photon wavepackets.
[1] Hong, Ou, Mandel, Phys. Rev. Lett. 59, 2044 (1987),
[2] Münzberg et al., PRX Quantum 2, 020326 (2021),
[3] Faleo et al., Sci. Adv. 10, eadp9030 (2024),
[4] Münzberg et al., APL Photonics 7, 070802 (2022)
[1] Hong, Ou, Mandel, Phys. Rev. Lett. 59, 2044 (1987),
[2] Münzberg et al., PRX Quantum 2, 020326 (2021),
[3] Faleo et al., Sci. Adv. 10, eadp9030 (2024),
[4] Münzberg et al., APL Photonics 7, 070802 (2022)
2025-04-10 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 11:15
Marek Szczepańczyk (IFT UW)The quest to detect (exceptional) gravitational-wave sources
Gravitational Wave Astrophysics has already demonstrated its potential to explore the Universe, but we are still at the beginning of this journey. While we regularly observe gravitational waves from compact binaries, we do not know what we may discover next. In my talk, I will give an overview of the field of Gravitational Wave Astrophysics by discussing the gravitational-wave detectors (current status and the future), the sources (standard and exceptional), and the role of model-independent searches in the exploration of the Universe. I will announce an upcoming LIGO-Virgo-KAGRA Symposium in Warsaw on core-collapse supernovae - one of the most interesting sources of gravitational waves. Finally, I will explore interesting venues for the field of gravitational waves.
2025-04-03 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 11:15
Piotr Dulian (IFT UW)QMetro++ - Python package for large scale quantum metrology
2025-03-27 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 11:15
Karolina Słowik (UMK Toruń)On the role of entanglement in two-photon absorption
Optimal excitation of a three-level ladder-type atom by a two-photon light state is analyzed using the Wigner-Weisskopf approximation. The optimal state, enabling perfect excitation with unit probability, is determined by the lifetimes of atomic states, with its entanglement dependent on their ratio. Two distinct interaction regimes are identified, in which entanglement affects the excitation process differently.
The optimal light state is an entangled photon pair. As such states may be challenging to prepare, comparisons are made with experimentally accessible photon pair profiles, whose parameters are optimized to maximize excitation probability. The influence of entanglement on atom excitation and its dependence on atomic properties are discussed.
The optimal light state is an entangled photon pair. As such states may be challenging to prepare, comparisons are made with experimentally accessible photon pair profiles, whose parameters are optimized to maximize excitation probability. The influence of entanglement on atom excitation and its dependence on atomic properties are discussed.
2025-03-20 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 11:15
Sumit Chaudhary (Technical University of Munich)Integration of QKD with classical channels using wavelength division multiplexing
2025-03-13 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 11:15
Sylwia Kolenderska (University of Auckland)Fourier-domain Quantum Optical Coherence Tomography for a fast tomographic quantum imaging
2025-03-06 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 11:15
Piotr Szańkowski (IFPAN)A perturbation theory for multi-time correlations in open systems
Dynamical maps are the principal subject of the open system theory. Formally, the dynamical map of a given open quantum system is a density matrix transformation that takes any initial state and sends it to the state at a later time. Physically, it encapsulates the system's evolution due to coupling with its environment.
Hence, with its dynamical map methods, the theory provides a flexible and accurate framework for computing expectation values of system observables. However, expectation values---or more generally, single-time correlation functions---capture only the simplest aspects of a quantum system's dynamics. A complete characterization requires access to multi-time correlation functions as well. For closed systems, such correlations are well-defined, even though knowledge of the system's state alone is insufficient to determine them fully. In contrast, the standard dynamical map formalism for open systems does not account for multi-time correlations, as it is fundamentally limited to describing state evolution.
Here, we extend the scope of open quantum system theory by developing a systematic perturbation theory for computing multi-time correlation functions.
[1] arXiv:2502.19137
Hence, with its dynamical map methods, the theory provides a flexible and accurate framework for computing expectation values of system observables. However, expectation values---or more generally, single-time correlation functions---capture only the simplest aspects of a quantum system's dynamics. A complete characterization requires access to multi-time correlation functions as well. For closed systems, such correlations are well-defined, even though knowledge of the system's state alone is insufficient to determine them fully. In contrast, the standard dynamical map formalism for open systems does not account for multi-time correlations, as it is fundamentally limited to describing state evolution.
Here, we extend the scope of open quantum system theory by developing a systematic perturbation theory for computing multi-time correlation functions.
[1] arXiv:2502.19137
2025-02-27 (Czwartek)
Zapraszamy do sali 0.06, ul. Pasteura 5 o godzinie 11:15
Alexandre Orthey (IPPT PAN)Certification of quantum states and measurements: how to deal with higher dimensions and more particles
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