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
2021-03-25 (Czwartek)
Zapraszamy na spotkanie o godzinie 11:15 
Alexander Lvovsky (University of Oxford)Neural networks for optics and optics for neural networks
Zoom link: https://zoom.us/j/6526721604?pwd=Y0pPdE9vT1hNWWNiZVBMaEVOeHN2dz09
Optics and machine learning are natural symbionts. I will present three examples of how these fields can benefit each other based on our recent experimental work: optical neural networks and their all-optical training, robotic alignment of optical experiments, application of machine learning in linear-optical far-field superresolution imaging.
Optics and machine learning are natural symbionts. I will present three examples of how these fields can benefit each other based on our recent experimental work: optical neural networks and their all-optical training, robotic alignment of optical experiments, application of machine learning in linear-optical far-field superresolution imaging.
2021-03-18 (Czwartek)
Zapraszamy na spotkanie o godzinie 11:15
Chandan Datta (CENT QOT UW)Catalytic Entanglement
2021-03-11 (Czwartek)
Zapraszamy na spotkanie o godzinie 11:15
Patryk Lipka-Bartosik (University of Bristol)All states are universal catalysts in quantum thermodynamics
Zoom link: https://zoom.us/j/6526721604?pwd=Y0pPdE9vT1hNWWNiZVBMaEVOeHN2dz09
Quantum catalysis is a fascinating concept which demonstrates that certain transformations can only become possible when given access to a specific resource that has to be returned unaffected. It was first discovered in the context of entanglement theory and since then applied in a number of resource-theoretic frameworks, including quantum thermodynamics. Although in that case the necessary (and sometimes also sufficient) conditions on the existence of a catalyst are known, almost nothing is known about the precise form of the catalyst state required by the transformation. In particular, it is not clear whether it has to have some special properties or be finely tuned to the desired transformation. In this work we describe a surprising property of multi-copy states: we show that in resource theories governed by majorization all resourceful states are catalysts for all allowed transformations. In quantum thermodynamics this means that the so-called "second laws of thermodynamics" do not require a fine-tuned catalyst but rather any state, given sufficiently many copies, can serve as a useful catalyst. These analytic results are accompanied by several numerical investigations that indicate that neither a multi-copy form nor a very large dimension catalyst are required to activate most allowed transformations catalytically. Based on arXiv: 2006.16290.
Quantum catalysis is a fascinating concept which demonstrates that certain transformations can only become possible when given access to a specific resource that has to be returned unaffected. It was first discovered in the context of entanglement theory and since then applied in a number of resource-theoretic frameworks, including quantum thermodynamics. Although in that case the necessary (and sometimes also sufficient) conditions on the existence of a catalyst are known, almost nothing is known about the precise form of the catalyst state required by the transformation. In particular, it is not clear whether it has to have some special properties or be finely tuned to the desired transformation. In this work we describe a surprising property of multi-copy states: we show that in resource theories governed by majorization all resourceful states are catalysts for all allowed transformations. In quantum thermodynamics this means that the so-called "second laws of thermodynamics" do not require a fine-tuned catalyst but rather any state, given sufficiently many copies, can serve as a useful catalyst. These analytic results are accompanied by several numerical investigations that indicate that neither a multi-copy form nor a very large dimension catalyst are required to activate most allowed transformations catalytically. Based on arXiv: 2006.16290.
2021-03-04 (Czwartek)
Zapraszamy na spotkanie o godzinie 11:15
Geza Toth (University of the Basque Country UPV EHU, Bilbao)Activating hidden metrological usefulness
Zoom link: https://zoom.us/j/6526721604?pwd=Y0pPdE9vT1hNWWNiZVBMaEVOeHN2dz09
We consider bipartite entangled states that cannot outperformseparable states in any linear interferometer. Then, we show thatthese states can still be more useful metrologically than separablestates if several copies of the state are provided or an ancilla isadded to the quantum system. We present a general method to find thelocal Hamiltonian for which a given quantum state performs the bestcompared to separable states. We obtain analytically the optimalHamiltonian for some quantum states with a high symmetry. We show thatall bipartite entangled pure states outperform separable states inmetrology. Some potential applications of the results are alsosuggested.
[1] G. Toth, T. Vertesi, P. Horodecki, and R. Horodecki, Phys. Rev.Lett. 125, 020402 (2020).
We consider bipartite entangled states that cannot outperformseparable states in any linear interferometer. Then, we show thatthese states can still be more useful metrologically than separablestates if several copies of the state are provided or an ancilla isadded to the quantum system. We present a general method to find thelocal Hamiltonian for which a given quantum state performs the bestcompared to separable states. We obtain analytically the optimalHamiltonian for some quantum states with a high symmetry. We show thatall bipartite entangled pure states outperform separable states inmetrology. Some potential applications of the results are alsosuggested.
[1] G. Toth, T. Vertesi, P. Horodecki, and R. Horodecki, Phys. Rev.Lett. 125, 020402 (2020).
2021-01-28 (Czwartek)
Zapraszamy na spotkanie o godzinie 11:15
Karol Łukanowski (QOT UW)Capacity of a lossy photon channel with direct detection
2021-01-21 (Czwartek)
Zapraszamy na spotkanie o godzinie 11:15
Nicolas Fabre (QOT CENT)Quantum Information in time-frequency continuous variables
2021-01-14 (Czwartek)
Zapraszamy na spotkanie o godzinie 11:15
Michał Oszmaniec (CFT PAN)Fermion Sampling: a robust quantum computational advantage scheme using fermionic linear optics and magic input states
ZOOM link: https://zoom.us/j/6526721604?pwd=Y0pPdE9vT1hNWWNiZVBMaEVOeHN2dz09
Fermionic Linear Optics (FLO) is a restricted model of quantum computation which in its original form is known to be efficiently classically simulable. We show that, when initialized with suitable input states, FLO circuits can be used to demonstrate quantum computational advantage with strong hardness guarantees. Based on this, we propose a quantum advantage scheme which is a fermionic analogue of Boson Sampling: Fermion Sampling with magic input states.
We consider in parallel two classes of circuits: particle-number conserving (passive) FLO and active FLO that preserves only fermionic parity and is closely related to Matchgate circuits introduced by Valiant. Mathematically, these classes of circuits can be understood as fermionic representations of the Lie groups U(d) and SO(2d). This observation allows us to prove our main technical results. We first show anticoncentration for probabilities in random FLO circuits of both kind. Moreover, we prove robust average-case hardness of computation of probabilities. To achieve this, we adapt the worst-to-average-case reduction based on Cayley transform, introduced recently by Movassagh, to representations of low-dimensional Lie groups. Taken together, these findings provide hardness guarantees comparable to the paradigm of Random Circuit Sampling.
Importantly, our scheme has also a potential for experimental realization. Both passive and active FLO circuits are relevant for quantum chemistry and many-body physics and have been already implemented in proof-of-principle experiments with superconducting qubit architectures. Preparation of the desired quantum input states can be obtained by a simple quantum circuit acting independently on disjoint blocks of four qubits and using 3 entangling gates per block. We also argue that due to the structured nature of FLO circuits, they can be efficiently certified using resources scaling polynomially with the system size.
The presentation is based on arXiv:2012.15825 , a paper written together with Ninnat Dangniam, Mauro Morales and Zoltan Zimboras
Fermionic Linear Optics (FLO) is a restricted model of quantum computation which in its original form is known to be efficiently classically simulable. We show that, when initialized with suitable input states, FLO circuits can be used to demonstrate quantum computational advantage with strong hardness guarantees. Based on this, we propose a quantum advantage scheme which is a fermionic analogue of Boson Sampling: Fermion Sampling with magic input states.
We consider in parallel two classes of circuits: particle-number conserving (passive) FLO and active FLO that preserves only fermionic parity and is closely related to Matchgate circuits introduced by Valiant. Mathematically, these classes of circuits can be understood as fermionic representations of the Lie groups U(d) and SO(2d). This observation allows us to prove our main technical results. We first show anticoncentration for probabilities in random FLO circuits of both kind. Moreover, we prove robust average-case hardness of computation of probabilities. To achieve this, we adapt the worst-to-average-case reduction based on Cayley transform, introduced recently by Movassagh, to representations of low-dimensional Lie groups. Taken together, these findings provide hardness guarantees comparable to the paradigm of Random Circuit Sampling.
Importantly, our scheme has also a potential for experimental realization. Both passive and active FLO circuits are relevant for quantum chemistry and many-body physics and have been already implemented in proof-of-principle experiments with superconducting qubit architectures. Preparation of the desired quantum input states can be obtained by a simple quantum circuit acting independently on disjoint blocks of four qubits and using 3 entangling gates per block. We also argue that due to the structured nature of FLO circuits, they can be efficiently certified using resources scaling polynomially with the system size.
The presentation is based on arXiv:2012.15825 , a paper written together with Ninnat Dangniam, Mauro Morales and Zoltan Zimboras
2021-01-07 (Czwartek)
Zapraszamy do sali 1.03, ul. Pasteura 5 o godzinie 11:15
Julia Amoros Binefa (QOT CENT)Noisy Magnetometry in the Linear-Gaussian Regime
2020-12-17 (Czwartek)
Zapraszamy na spotkanie o godzinie 11:15
Guillaume Thekkadath (University of Oxford)Photon counting for quantum state engineering and interferometry
A longstanding goal in quantum optics has been to realize a photon-number-resolvingdetector that efficiently counts the number of photons in a field. This goalhas been largely met with the development of transition edge sensors which cancount up to roughly 15 photons with efficiencies over 95% [1]. In this talk, I will present experimental work employing these detectors for characterizing and engineering quantum states of light. In a first experiment, we build a “weak-field homodyne” detector by replacing the photodiodes conventionally used in homodyne detection with transition edge sensors. We show that this detector can tune between photon-number and quadrature measurements by changing the strength of the local oscillator [2]. This tunability enables the detector to project light onto a wide range of states, including superpositions of coherent states, i.e. optical Schrödinger cat states. In a second experiment, we use transition edge sensors and high-gain parametric down-conversion sources to prepare and detect large Fock states for quantum-enhanced interferometry [3].
[1] Opt. Exp. 16 3032-3040 (2008)
[2] Phys. Rev. A 101 031801(R) (2020)
[3] npj Quantum Inf. 6 89 (2020)
ZOOM link: https://zoom.us/j/6526721604?pwd=Y0pPdE9vT1hNWWNiZVBMaEVOeHN2dz09
[1] Opt. Exp. 16 3032-3040 (2008)
[2] Phys. Rev. A 101 031801(R) (2020)
[3] npj Quantum Inf. 6 89 (2020)
ZOOM link: https://zoom.us/j/6526721604?pwd=Y0pPdE9vT1hNWWNiZVBMaEVOeHN2dz09
2020-12-10 (Czwartek)
Zapraszamy na spotkanie o godzinie 11:15
Marti Perarnau Llobet (University of Geneva)Weakly invasive metrology: quantum advantage and physical implementations
We consider the estimation of a Hamiltonian parameter of a set of highly photosensitive samples, which are damaged after a few photons Nabs are absorbed. The samples are modelled as a two mode photonic system, where photons simultaneously acquire information on the unknown parameter and are absorbed at a fixed rate. The shot-noise limit implies that arbitrarily intense coherent states can obtain information at a rate that scales at most linearly with Nabs, whereas quantum states with finite intensity can surpass this bound. In particular, few-photon entangled states can overcome arbitrary classical strategies when Nabs is small, and we characterize the quantum advantage as a function of Nabs and N (the number of photons in the quantum state). We also consider the robustness of the advantage under imperfect measurements and finite preparation rate of quantum states. Finally, we consider an implementation of these quantum advantages in cavity QED, where Fock states are both prepared and measured by coupling atomic ensembles to the cavities. In this platform, Dicke superradiance can be exploited for preparing and measuring photonic states fast and with high efficiency.This talk is based on arXiv:2006.12114, joint work with Daniel Malz and Ignacio Cirac.
ZOOM link: https://zoom.us/j/6526721604?pwd=Y0pPdE9vT1hNWWNiZVBMaEVOeHN2dz09
ZOOM link: https://zoom.us/j/6526721604?pwd=Y0pPdE9vT1hNWWNiZVBMaEVOeHN2dz09
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