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
2020-03-12 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15 
Radek Łapkiewicz (IFD UW)ODWOLANE/CANCELED. What can photon pair detection do for super-resolution microscopy and phase imaging?
Quantum imaging typically requires the preparation of fragile states of light with which the sample is illuminated. An entirely different scheme, in which the sample itself “prepares” the quantum state required for imaging, was proposed and demonstrated by Schwartz and colleagues [1, 2]. Their quantum correlation microscopy method relies on photon antibunching and allows improving the resolution by the factor of \sqrt(2), beyond the diffraction limit. This is achieved by replacing the standard intensity measurement with the measurement of the number of photon pairs which are missing due to photon antibunching. In general, n-th order correlations, provide the resolution improvement by the factor of \sqrt(n). Interestingly, most of the fluorophores used in microscopy exhibit photon antibunching and, as a consequence, can be used in quantum correlation microscopy. Recently, this method has been combined with image scanning microscopy, a super-resolution microscopy technique, and used to obtain super-resolved images of a biological sample [3]. A classical analog of the quantum correlation microscopy turned out to offer a similar resolution improvement and required measurement times shorter by an order of magnitude [4].
We will introduce the basics of quantum and classical correlation microscopy and discuss its implementations. The second part of the talk will be devoted to interferometric phase imaging enabled by photon correlation measurements.
Interferometric methods are essential for making precise measurements and typically require high coherence between the measured and the reference beam. When the phase offset between the two beams changes randomly, the interferogram averages out, erasing all the spatial phase information. We will show that, even when the lowest order interference fringes cannot be observed, spatial phase of a beam can be measured. This is achieved by spatially resolved photon counting and the analysis of a photon pair detection probability distribution [5]. These results demonstrate that information contained in photon correlations enables phase imaging in conditions in which traditional methods fail.
[1] O. Schwartz, D. Oron, Improved resolution in fluorescence microscopy using quantum correlations, Phys. Rev. A 85, 033812 (2012).
[2] O. Schwartz et al. Superresolution microscopy with quantum emitters, Nano Lett. 13, 5832–5836 (2013).
[3] R. Tenne, et al., Super-resolution enhancement by quantum image scanning microscopy, Nat. Phot., 13, 116–122 (2019).
[4] A. Sroda, et al., Super-resolution optical fluctuation image scanning microscopy (SOFISM), arXiv:2002.00182 (2020).
[5] J. Szuniewicz et al., Noise Resistant Phase Imaging with Intensity Correlation, Rochester Conference on Coherence and Quantum Optics (2019).
We will introduce the basics of quantum and classical correlation microscopy and discuss its implementations. The second part of the talk will be devoted to interferometric phase imaging enabled by photon correlation measurements.
Interferometric methods are essential for making precise measurements and typically require high coherence between the measured and the reference beam. When the phase offset between the two beams changes randomly, the interferogram averages out, erasing all the spatial phase information. We will show that, even when the lowest order interference fringes cannot be observed, spatial phase of a beam can be measured. This is achieved by spatially resolved photon counting and the analysis of a photon pair detection probability distribution [5]. These results demonstrate that information contained in photon correlations enables phase imaging in conditions in which traditional methods fail.
[1] O. Schwartz, D. Oron, Improved resolution in fluorescence microscopy using quantum correlations, Phys. Rev. A 85, 033812 (2012).
[2] O. Schwartz et al. Superresolution microscopy with quantum emitters, Nano Lett. 13, 5832–5836 (2013).
[3] R. Tenne, et al., Super-resolution enhancement by quantum image scanning microscopy, Nat. Phot., 13, 116–122 (2019).
[4] A. Sroda, et al., Super-resolution optical fluctuation image scanning microscopy (SOFISM), arXiv:2002.00182 (2020).
[5] J. Szuniewicz et al., Noise Resistant Phase Imaging with Intensity Correlation, Rochester Conference on Coherence and Quantum Optics (2019).
2020-02-27 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15
Bohnishikha Ghosh (IFD UW)Advantage in two-way communication using non-classical states of light
The advantage of using a single-photon embedded in a two-mode entangled state in two-way communication via maximal violation of an inequality associated with the ‘Guess Your Neighbour’s Input’ (GYNI) game has been theoretically [Phys. Rev. Lett. 120, 060503 (2018)] as well as experimentally [CLEO FID.4 (OSA, 2018)] established recently. We argue that such an advantage can also be obtained using any single-mode pure non-classical state embedded in a two-mode pure entangled state, wherein the other mode is the vacuum (henceforth referred to as a generalized NOON state), regardless of the average photon number of the single mode state. For the special cases of the even-coherent, odd-coherent, and squeezed vacuum NOON states, we establish that the advantage is also maximal. We also show that the usage of the even-coherent NOON states can provide an advantage over the single photon two-mode entangled state under noisy apparatuses (beam splitter and photo detectors). As an aside, we study how some of these generalized NOON states fare in terms of violation of a reference-frame independent Bell-type inequality.
2020-01-30 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15
Farid Khalili (Lomonosov Moscow State University)Non-classical light in laser gravitational wave detectors (room changed!!! CENT AULA 00.142)
Quantum mechanics applies a hierarchy of limitations on the precision of optical interferometric measurements. The most well-known one is the Shot Noise Limit (SNL) which originates from the phase fluctuation of the probing light. If the optical power is high enough then perturbation of the mirrors mechanical motion imposed by the light power fluctuations also becomes important, leading to the Standard Quantum Limit (SQL). Methods for suppressing or avoiding these fluctuations based on non-classical states of light are under active development now. The simplest of them, which can overcome the SNL (but not SQL), namely the injection of squeezed light into the interferometer, is already used in the modern gravitational-waves detectors. More sophisticated methods, like frequency-dependent squeezing, are considered for implementation in future detectors. The goal of my talk is to provide a brief review of these projects.
2020-01-23 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15
Krzysztof Chabuda (IFT UW)Crash Course on Tensor Networks
2020-01-16 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15
Francesco Albarelli (IFT UW)Recent advances in multiparameter quantum estimation
2019-12-19 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15
Stanisław Kurdziałek (IFT UW)Fundamental resolution limits in imaging of sources with fluctuating brightness
2019-12-12 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15
Carlo Maria Scandolo (University of Calgary, Canada)The entanglement of a bipartite channel
The most general quantum object that can be shared between two distant parties is a bipartite quantum channel. While much effort over the last two decades has been devoted to the study of entanglement of bipartite states, very little is known about the entanglement of bipartite channels. In this work, for the first time we rigorously study the entanglement of bipartite channels. We follow a top-down approach, starting from general resource theories of processes, for which we present a new construction of a complete family of monotones, valid in all resource theories where the set of free superchannels is convex. In this setting, we define various general resource-theoretic protocols and resource monotones, which are then applied to the case of entanglement of bipartite channels. We focus in particular on the resource theory of NPT entanglement. Our definition of PPT superchannels allows us to express all resource protocols and monotones in terms of semi-definite programs. Along the way, we generalize the negativity measure to bipartite channels, and show that another monotone, the max-logarithmic negativity, has an operational interpretation as the exact asymptotic entanglement cost of a bipartite channel. Finally, we show that it is not possible to distill entanglement out of bipartite PPT channels under any set of free superchannels that can be used in entanglement theory, leading us in particular to the discovery of bound entangled POVMs.
2019-12-05 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15
Michal Parniak (Niels Bohr Institute, University of Copenhagen)Entangling macroscopic mechanical and spin oscillators
Quantum optomechanics allows cooling of mechanical harmonic oscillators close to their ground states, thus facilitating probing of quantum properties of macroscopic systems. We engineer a hybrid system consisting of such a mechanical resonator, a phononic crystal patterned SiN membrane, and a large Cesium spin ensemble coupled via light, to study entanglement of two distinct macroscopic systems. To optimally track the evolution of the hybrid system in the presence of highly non-white noise we develop an approach based on a quantum version of the Wiener filter, which is a Kalman filter operating for a time-stationary signal. Optimal tracking and entanglement entail applications in quantum-enhanced force sensing.
2019-11-28 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15
Andrzej Dragan (IFT UW)Quantum principle of relativity
2019-11-21 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15
Michał Oszmaniec (CFT PAN)Epsilon-nets, unitary t-designs and random quantum circuits
Epsilon-nets and approximate unitary t-designs are natural notions that capture properties of general unitary operations relevant for numerous applications in quantum information and quantum computing. The former constitute subsets of unitary channels that are epsilon-close to every target unitary channel. The latter are ensembles of unitaries that (approximately) recover Haar averages of polynomials in entries of unitary channels up to order t.In this work we establish quantitative connections between these two seemingly different notions. We apply our findings in conjunction with the recent results of [Varju, 2013] in the context of quantum computing. First, we show that that approximate t-designs can be generated by shallow random circuits formed any from set of universal two-qudit gates in the parallel and sequential local architectures considered by [Brandao-Harrow-Horodecki, 2016]. Importantly, we do not require that the gate set is symmetric (i.e. contains gates together with their inverses) and consists of gates having algebraic entries. Second, we consider a problem of compilation of quantum gates and prove a non-constructive version of Solovay-Kitaev theorem for general universal gate sets.
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