Quantum Technologies exploit the ability to prepare, manipulate and detect single quantum objects such as atoms, photons and electrons to enhance the performance of applications in quantum communications, quantum computing and simulation, and quantum sensing/metrology. In the last decades impressive progress has been made in a large variety of physical systems providing an excellent experimental test bench for novel concepts introduced within the framework of quantum information science theory and opening the path to new devices for advanced quantum technologies.

The aim of the Quantum Technologies Conference is to bring together people from academia and industry who are active in this field or have an interest in new emerging areas. We appreciate contributions ranging from basic research on quantum components and systems to industrial development of quantum-based products, prototypes and instruments:

The conference program will consist of oral and poster presentations on topics that include, but are not limited to:

  • quantum cryptography and communication
  • quantum simulation and computing (hardware and software)
  • quantum sensing/imaging/metrology (e.g. atomic clocks, quantum enhanced measurements using entangled or correlated light, novel applications)
  • novel quantum platforms and hybrid devices (based on atoms, ions, molecules, impurities, optical, mechanical, semiconductor and other solid-state systems, integrated photonics circuits and devices)
  • quantum technology-based instruments and their applications
  • quantum components and their applications (such as single photon sources, entangled light sources, quantum memories, photon detectors, random number generators ...).
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    In progress – view active session
    Conference 12133

    Quantum Technologies 2022

    4 - 6 April 2022
    View Session ∨
    • 1: Quantum Sensing and Metrology I
    • 2: Quantum Sensing and Metrology II
    • 3: Quantum Components and their Applications I
    • 4: Quantum Cryptography and Communication I
    • 5: Quantum Cryptography and Communication II
    • 6: Quantum Sensing and Metrology III
    • Posters-Tuesday
    • 7: Novel Quantum Platforms and Hybrid Devices I
    • 8: Novel Quantum Platforms and Hybrid Devices II
    • 9: Quantum Components and their Applications II
    • 10: Quantum Simulation and Computing


    • Submissions are accepted through 07-February
    • Notification of acceptance by 21-February

    Call for Papers Flyer
    Session 1: Quantum Sensing and Metrology I
    4 April 2022 • 11:30 AM - 12:40 PM CEST
    TBA1 (Invited Paper)
    4 April 2022 • 11:30 AM - 12:00 PM CEST
    Author(s): Marco Genovese, Istituto Nazionale di Ricerca Metrologica (Italy)
    4 April 2022 • 12:00 PM - 12:20 PM CEST
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    First temperature measurement in neurons by ODMR techniques G.Petrini, G.Tomagra, E.Bernardi, E,. Moreva, I.P.Degiovanni, P.Traina, P.Olivero, V.Carabelli, M.Genovese In this talk I will present our results that demonstrate for the first time the possibility of making localized temperature measurement with precision under 0.1 K in neurons by exploiting ODMR techniques. After a general introduction to ODMR techniques based on NV colour centers in diamond, I will present this breakthrough result that will have huge impact to biology and medicine. In little more detail, we probe temperature variations at single-cell scale using color centers in nanodiamonds. We activate the firing of a neuronal network using a drug that stops the inhibitory mechanism. In these conditions, we detect a significant local temperature increase. We associate the observed temperature increase to the firing state of the network, since no significant increase is observed in cases when the drug is not injected. We discuss the possible physiological mechanisms that causes the heat production leading to the observed temperature increase. In perspective, this phenomenon could be extremely promising as a mean of indirect detection of the action potential in future experiments in which the nanodiamonds are functionalized in order to target specific ions channels.
    Author(s): Nicolas Fabre, Ctr. for Quantum Optical Technologies, Ctr. of New Technologies, Univ. of Warsaw (Poland), Univ. Complutense de Madrid (Spain)
    4 April 2022 • 12:20 PM - 12:40 PM CEST
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    Hong-Ou-Mandel interferometry takes advantage of the quantum nature of two-photon interference to increase the resolution of precision measurements of time-delays. Relying on few-photon probe states, this approach is applicable also in cases of extremely sensible samples and it achieves attosecond (nanometer path length) scale resolution, which is relevant to cell biology and two-dimensional materials. Here, we theoretically analyze how the precision of Hong-Ou-Mandel interferometers can be significantly improved by engineering the spectral distribution of two-photon probe states. In particular, we assess the metrological power of different classes of biphoton states with non-Gaussian time-frequency spectral distributions, considering the estimation of both time-and frequency-shifts. We find that grid states, characterized by a periodic structure of peaks in the chronocyclic Wigner function, can outperform standard biphoton states in sensing applications. The considered states can be feasibly produced with atomic photon sources, bulk non-linear crystals and integrated photonic waveguide devices.
    Session 2: Quantum Sensing and Metrology II
    4 April 2022 • 1:50 PM - 3:10 PM CEST
    Author(s): John Jeffers, Gioan Tatsi, Univ. of Strathclyde (United Kingdom); Ugo Zanforlin, Gerald S. Buller, Heriot-Watt Univ. (United Kingdom)
    4 April 2022 • 1:50 PM - 2:10 PM CEST
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    An image can be extracted from a beam of light that has not interacted with the imaged object, a technique known as ghost imaging [1]. Here we describe, for the first time, a related technique in which a coherent amplitude can be imprinted nonlocally on to a beam that has no prior phase information. We call this technique ghost displacement. We have also successfully performed the first experimental demonstration. The technique could have applications in the sharing of quantum information and in imaging. The key is to measure one of a correlated pair of beams in the coherent state basis. This can be simply accomplished via a displacement coupled with obtaining no click at a Geiger-mode detector. The displacement is performed by placing a highly transmitting beam splitter in front of the detector and using this to mix in a coherent state. When the no click measurement result is obtained it imprints a coherent amplitude of the opposite phase to the displacement on the other correlated beam, at the expense of reducing its thermal component. Our experiment uses a fibre-based nested interferometric set-up to imprint both amplitude and phase information on an output state with thermal statistics produced by modulating the amplitude and phase of an 842nm VCSEL that is run at a 1MHz pulse repetition rate. We do this by conditioning on the results of measurements performed in an arm of the experiment that does not interact with the output. We check the properties of the output using a tomographic stage. Our experiment shows almost perfect agreement with theory. [1] M. J. Padgett and R. W. Boyd, An introduction to ghost imaging: quantum and classical, Phil. Trans. Roy. Soc. 375, 20160233 (2017).
    Author(s): Monika E. Mycroft, Univ. of Warsaw (Poland); Guillaume S. Thekkadath, Bryn A. Bell, Chris G. Wade, Andreas Eckstein, David S. Phillips, Raj B. Patel, Clarendon Lab., Univ. of Oxford (United Kingdom); Adam Buraczewski, Univ. of Warsaw (Poland); Adriana E. Lita, Thomas Gerrits, Sae W. Nam, National Institute of Standards and Technology (United States); Magdalena Stobinska, Univ. of Warsaw (Poland); Alex I. Lvovsky, Clarendon Lab., Univ. of Oxford (United Kingdom); Ian A. Walmsley, Clarendon Lab., Univ. of Oxford (United Kingdom), Imperial College London (United Kingdom)
    4 April 2022 • 2:10 PM - 2:30 PM CEST
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    Optical phase measurements are inherently limited by quantum fluctuations in light known as the shot noise limit. Some quantum states allow us to overcome that limit but they are found to be either vulnerable to decoherence or their creation is challenging. In my talk I will introduce novel probe states which are easy to generate but surpass the shot noise limit even in the presence of substantial photonic losses. The states are created by combining two heralded photon-number states, not necessarily equal, in an interferometer where the optical phase is to be estimated. We characterize our probes based on two parameters: the total number of photons detected in the heralded modes and the photon number difference between the two modes. We show that for a given total number of photons the probes approximate the performance of the optimal states as a function of losses in the interferometer. The photon number difference determines the best photon number configuration for a particular range of losses. Larger photon numbers allow us to be more accurate in determining that range and are thus desirable. We experimentally implement our scheme using high-gain parametric down-conversion sources and state-of-the-art photon-number-resolving detectors in order to access a large photon-number regime. We herald entangled probes of sizes up to N=8 and measure up to 16-photon coincidences. Although due to experimental imperfections we were not able to surpass the shot noise limit without postselection, we demonstrate that our probes' sensitivity derives from multiphoton interference and that they are robust to losses. We thus pave the way towards implementing multiphoton quantum technologies in real-life applications.
    Author(s): Carlos E. Lopetegui, Lab. Kastler Brossel, École normale supérieure - PSL, CNRS (France), Sorbonne Univ, (France), Collège de France (France); Manuel Gessner, Lab. Kastler Brossel, Ecole normale supérieure - PSL, CNRS (France), Sorbonne Univ. (France), Collège de France (France); Matteo Fadel, Univ. Basel (Switzerland); Nicolas Treps, Lab. Kastler Brossel, Ecole normale supérieure - PSL, CNRS (France), Sorbonne Univ. (France), Collège de France (France); Mattia Walschaers, Lab. Kastler Brossel, Ecole normale supérieure - PSL, CNRS (France), Sorbonne Univ. (France), Collège de France (France)
    4 April 2022 • 2:30 PM - 2:50 PM CEST
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    Recent developments, such as the experimental realization of large-scale cluster states, have built a valid case for continuous-variable quantum optics as a promising platform for quantum information processing. The capability of creating non-Gaussian states is key to building a universal quantum computer and achieving a quantum computational advantage. On the other hand, quantum correlations are also at the core of current developments in quantum technologies. Yet, quantum correlations in non-Gaussian states are still poorly understood for continuous-variable systems. In this contribution we will focus on quantum steering, where Alice and Bob each share a part of bipartite quantum state and perform local measurements on their respective subsystem. Quantum steering from Alice to Bob occurs when Bob can exploit information from Alice’s measurements to infer the outcome of his observables’ measurement more precisely than allowed by classical correlations. The paradigmatic example for this phenomenon is found when Alice and Bob both measure field quadratures. In this case, Bob can construct conditional variances that violate Heisenberg’s inequality. This violation, known as Reid’s criterion, is a signature of quantum steering that relies purely on Gaussian features of the state. More generally, we speak of Gaussian steering when we can violate steering inequality using only information from the state’s covariance matrix. For non-Gaussian states, the covariance matrix only offers limited information about the state, and many properties remain under the radar. Therefore, certification protocols of quantum steering for non-Gaussian states are scarce and generally highly demanding from an experimental point of view. In this contribution, we use a recently established connection between quantum steering and the (quantum) Fisher information to develop a new protocol for detection of quantum steering in non-Gaussian. This protocol relies exclusively on homodyne measurements.
    Author(s): Shikang Liu, Pascal Neveu, Louka Hemmen, Univ. Paris-Saclay (France); Etienne Brion, Univ. Paul Sabatier (France); E. Wu, East China Normal Univ. (China); Fabien Bretenaker, Fabienne Goldfarb, Univ. Paris-Saclay (France)
    4 April 2022 • 2:50 PM - 3:10 PM CEST
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    Spin noise spectroscopy (SNS) allows optically detect the fluctuations of a spin ensemble. Such fluctuations induce noise in the birefringence of the medium, which can be probed by recording polarization fluctuations of a laser beam after its propagation through the sample. As spin fluctuations are centered on the zero frequency, a transverse magnetic field is applied: spin precession then shifts the spin noise resonance at the Larmor frequency, so that it is not hidden by technical noises. The first SNS experiment was reported in the early 1980s by Alexandrov and Zapasskii, but it is only in 2004 that advances in narrow linewidth lasers and low noise electronics allow using this technique to probe various systems, such as thermal atomic vapors, semiconductors, or quantum wells. It was also proposed for magnetic field sensing, and possible measurements of correlations beyond the second-order raise a lot of interest, as they can give access to new quantum phenomena. We have performed spin noise spectroscopy in a metastable helium gas cell, and show that we can get two polarization dependent noise peaks when we record the linear instead of the circular birefringence fluctuations. Moreover, the relatively simple structure of helium allows us to show that it depends on the closest optical transition even when we are detuned by more than the Doppler broadening. We can also show that the behavior of the polarization dependence is strongly affected by time dependent B-field fluctuations. We performed simulations using a density matrix time evolution model, with added random fluctuations. It reproduces quite well the experimental results, including the transition dependence and the time dependent B-field noise effect, which have not been reported yet.
    Session 3: Quantum Components and their Applications I
    4 April 2022 • 3:40 PM - 5:30 PM CEST
    TBA3 (Invited Paper)
    Author(s): Virginia D'Auria, Institut de Physique de Nice (France)
    4 April 2022 • 3:40 PM - 4:10 PM CEST
    Author(s): Emma Lomonte, Martin Wolff, Fabian Beutel, Simone Ferrari, Carsten Schuck, Wolfram Pernice, Francesco Lenzini, Westfälische Wilhelms-Univ. Münster (Germany)
    4 April 2022 • 4:10 PM - 4:30 PM CEST
    Author(s): Maria I. Amanti, Félicien Appas, Univ. de Paris (France); Aristide Lemaı̂tre, Ctr. de Nanosciences et de Nanotechnologies, Univ. Paris-Saclay, CNRS (France); Martina Morassi, Ctr. de Nanosciences et de Nanotechnologies, Univ. Paris-Saclay, CNRS (France); Florent Baboux, Sara Ducci, Univ. de Paris (France)
    4 April 2022 • 4:30 PM - 4:50 PM CEST
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    Integrated quantum photonics is a key tool towards large scale quantum technologies. In this work we present an AlGaAs-based photonic circuit for on-chip generation and manipulation of broadband polarization-entangled photon pairs. The quantum state is generated by Type-II spontaneous parametric down conversion in AlGaAs Bragg reflection waveguides at telecom wavelengths and room temperature. Polarization entangled photons are manipulated over a frequency band of around 50 nm by an integrated polarizing beam splitter. We demonstrate Hong-Ou-Mandel visibility of 80% for a quantum device where the photon pairs generation and manipulation are implemented in a single chip.
    Author(s): Petr Steindl, Kirsten Kanneworff, Victoria Domínguez Tubío, Wolfgang Löffler, Leiden Univ. (Netherlands)
    4 April 2022 • 4:50 PM - 5:10 PM CEST
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    The transition from quantum to classical state of light is of fundamental interest of quantum optics. For example, coherent states are considered to be the most classical form of light, but expressed in photon number (Fock) space, they consist of a complex superposition of a photon number states. Although no photon number states can be produced from coherent light using linear optics, the opposite is possible, as we have shown recently [1]. Here, we show a scheme for continuous indistinguishability-induced quantum-to-classical transition of photon statistics [2] using quantum interference of true single photons produced with a solid-state quantum dot cavity QED system, with weak laser light on an unbalanced beamsplitter. We study the experimental tuneability of the generated states by coherent state strength, single-photon brightness, and their mutual photon indistinguishability by characterizing the second-order correlation function of the generated mixed state. Combining this simple linear optics scheme with near-ideal sources of single photons [3], the generated quantum states of light could be useful for high-precision metrology [4] and advanced quantum communication protocols [5]. [1] P. Steindl, et al., Phys. Rev. Lett. 126, 143601 (2021) [2] A. Shen, et al., Phys. Rev. A 95, 053851 (2017) [3] H. Snijders, et al., Phys. Rev. Appl. 9, 031002 (2018) [4] D. Braun, et al., Phys. Rev. A 90, 013821 (2014) [5] D. Wang, et al., Phys. Rev. A 90, 062315 (2014)
    Author(s): Chang Li, Institut de Science et d'Ingénierie Supramoléculaires, Univ. de Strasbourg (France), CNRS (France)
    4 April 2022 • 5:10 PM - 5:30 PM CEST
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    For scalable quantum communication and networks, a key step is to realize a quantum repeater node that can efficiently connect different segments of atom-photon entanglement using quantum memories. We report a compact and hardware-efficient realization of a quantum repeater node using a single atomic ensemble for multicell quantum memories. A millisecond lifetime is achieved for individual memory cells after suppressing the magnetic-field-induced inhomogeneous broadening and the atomic-motion-induced spin-wave dephasing. Based on these long-lived memory cells, we achieve heralded asynchronous entanglement generation in two quantum repeater segments one after another and then an on-demand entanglement connection of these two repeater segments. As another application of the multicell atomic quantum memory, we further demonstrate storage and on-demand retrieval of heralded atomic spin-wave qubits by implementing a random access quantum memory with individual addressing capacity. This work provides a promising constituent for efficient realization of quantum repeaters for large-scale quantum networks.
    Session 4: Quantum Cryptography and Communication I
    5 April 2022 • 9:00 AM - 10:30 AM CEST
    TBA2 (Invited Paper)
    5 April 2022 • 9:00 AM - 9:30 AM CEST
    Author(s): Antariksha Das, Mohsen Falamarzi Askarani, Jacob H. Davidson, Gustavo C. Amaral, QuTech, Technische Univ. Delft (Netherlands); Neil Sinclair, Caltech (United States); Daniel Oblak, Institute for Quantum Science and Technology, Univ. of Calgary (Canada); Joshua A. Slater, Sara Marzban, QuTech, Technische Univ. Delft (Netherlands); Charles W. Thiel, Rufus L. Cone, Montana State Univ. (United States); Wolfgang Tittel, QuTech, Technische Univ. Delft (Netherlands)
    5 April 2022 • 9:30 AM - 9:50 AM CEST
    Author(s): Francesca Sansavini, Lab. Kastler Brossel, Sorbonne Univ., CNRS (France), Ecole normale supérieure - PSL (France), Collège de France (France); Matthieu Ansquer, Lab. Kastler Brossel, Sorbonne Univ, CNRS (France), Ecole normale supérieure - PSL (France), Collège de France (France); Tiphaine Kouadou, Nicolas Treps, Valentina Parigi, Lab. Kastler Brossel, Sorbonne Univ., CNRS (France), Ecole normale supérieure - PSL (France), Collège de France (France)
    5 April 2022 • 9:50 AM - 10:10 AM CEST
    Author(s): Jan-Michael Mol, In­sti­tut für Quan­ten­tech­no­lo­gi­en, Deutsches Zentrum für Luft- und Raumfahrt e.V. (Germany); Luisa Esguerra, Institut für Optische Sensorsysteme, Deutsches Zentrum für Luft- und Raumfahrt eV (Germany), Institut für Optik und Atomare Physik, Technische Univ. Berlin (Germany); Matthias Meister, In­sti­tut für Quan­ten­tech­no­lo­gi­en, Deutsches Zentrum für Luft- und Raumfahrt e.V. (Germany); Janik Wolters, Institut für Optische Sensorsysteme, Deutsches Zentrum für Luft- und Raumfahrt e.V. (Germany), Institut für Optik und Atomare Physik, Technische Univ. Berlin (Germany); Lisa Wörner, In­sti­tut für Quan­ten­tech­no­lo­gi­en, Deutsches Zentrum für Luft- und Raumfahrt e.V. (Germany)
    5 April 2022 • 10:10 AM - 10:30 AM CEST
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    Investigations into the foundations of quantum mechanics and their link to gravity and general relativity require sensitive quantum experiments. To provide ultimate insight, the realization of such experiments in space will sooner or later become a necessity. With their advanced state and backed by decades of development, quantum technologies and among them quantum memories are providing novel approaches to reach conclusive experimental results. We therefore want to highlight the use case of quantum memories for investigations of fundamental physics in space, and discuss both concrete experiments as well as platforms and performance of candidate quantum memories.
    Session 5: Quantum Cryptography and Communication II
    5 April 2022 • 11:00 AM - 12:40 PM CEST
    Author(s): Kirsten Kanneworff, Petr Steindl, Leiden Univ. (Netherlands); Rene Allerstorfer, Philip Verduyn Lunel, Florian Speelman, Harry Buhrman, QuSoft (Netherlands); Wolfgang Löffler, Leiden Univ. (Netherlands)
    5 April 2022 • 11:00 AM - 11:20 AM CEST
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    Authentication is an important, but also problematic part in communications, also in quantum key distribution (QKD). For many applications, certification of the geographical location of a party would be sufficient for authentication of a communication channel. By using fundamental physical laws, namely, the speed-of-light limit of information transfer, in combination with the no-cloning theorem of quantum mechanics [1], quantum position verification (QPV) protocols are found to be secure under the condition that attackers can only share a limited amount of pre-shared entanglement [2]. Here, we present an analysis of experimental considerations and possible limitations of a proposed loss-tolerant QPV protocol [3,4]. In particular, we consider the case where the quantum information is carried by true single photons created with a quantum dot cavity-QED source [5] using a cross-polarization technique [6] to eliminate the excitation laser. We study the implications of sending the photons through optical fibers, which would enable quantum position verification over long-distances, but puts additional restrictions on the security of QPV by the reduced speed of light. We find that a real-world demonstration of QPV is feasible. [1] A. Kent et al., Phys. Rev. A. 84, 012326 (2011) [2] H. Buhrman et al., SIAM J. Comput. 43, 150-178 (2014) [3] C.C.W. Lim et al., Phys. Rev. A. 94, 032315 (2016) [4] R. Allerstorfer et al., Arxiv: 2106.12911 (2021) [5] H. Snijders et al., Phys. Rev. A. 9, 031002 (2018) [6] H. Snijders et al., Phys. Rev. A. 101, 053811 (2020)
    Author(s): Marie Ioannou, Maria Ana Pereira, Davide Rusca, Fadri Grünenfelder, Alberto Boaron, Matthieu Perrenoud, Univ. de Genève (Switzerland); Alastair A. Abbott, Univ. Grenoble Alpes (France); Pavel Sekatski, Univ. de Genève (Switzerland); Jean-Daniel Bancal, Univ. Paris-Saclay (France), CEA (France), CNRS (France); Nicolas Maring, Hugo Zbinden, Nicolas Brunner, Univ. de Genève (Switzerland)
    5 April 2022 • 11:20 AM - 11:40 AM CEST
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    We present protocols for quantum key distribution in a prepare-and-measure setup with an asymmetric level of trust. While the device of the sender (Alice) is partially characterized, the receiver's (Bob's) device is treated as a black-box. The security of the protocols is based on the assumption that Alice's prepared states have limited overlaps, but no explicit bound on the Hilbert space dimension is required. The protocols are immune to attacks on the receiver's device, such as blinding attacks. The users can establish a secret key while continuously monitoring the correct functioning of their devices through observed statistics. We report a proof-of-principle demonstration, involving mostly off-the-shelf equipment, as well as a high-efficiency superconducting nanowire detector. A positive key rate is demonstrated over a 4.8km low-loss optical fiber with finite-key analysis. The prospects of implementing these protocols over longer distances is discussed.
    Author(s): Raphael Aymeric, Yves Jaouën, Cédric Ware, Romain Alléaume, Télécom Paris (France)
    5 April 2022 • 11:40 AM - 12:00 PM CEST
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    Among quantum key distribution (QKD) technologies, continuous-variable (CV) QKD is a promising candidate for large-scale deployment. CV-QKD bears many similarity, at hardware level, with modern classical coherent optical communications systems and its integration on existing telecom networks is greatly favoured by its good coexistence capability with WDM classical communications. This would greatly reduce deployment costs compared to building a dedicated infrastructure. A challenge for CV-QKD is carrier phase and frequency recovery which is usually tackled by relying on reference signals. In this work we demonstrate joint QKD and classical communications where the carrier information is recovered on the classical channel directly, removing the need for a dedicated reference signal and moving closer to CV-QKD integration over classical channels. Our demonstration was operated on a 15 km fibre link and provided an average excess noise of 0.009 shot-noise units on the quantum quadratures while maintaining reliable classical communications.
    Author(s): Nicola Massari, Fondazione Bruno Kessler (Italy)
    5 April 2022 • 12:00 PM - 12:20 PM CEST
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    A proof-of-concept of a monolithic QRNG based on SPAD is here presented. The proposed implementation allows to integrate in a single device source of light, detectors and logic for random number generation. The proposed cell consists of a central emitter and multiple detectors with a custom circuit for data validation in order to exclude possible unwanted events coming from noise. The achieved bit rate is in the order of few kbps.
    Author(s): Mohamed Faouzi Melalkia, Univ. Côte d’Azur (France), Institut de Physique de Nice, CNRS (France); Juliette Huynh, Univ. Côte d'Azur (France), Institut de Physique de Nice, CNRS (France); Léandre Brunel, Univ. Côte d’Azur (France), Institut de Physique de Nice, CNRS (France); Sébastien Tanzilli, Univ. Côte d’Azur (France), Institut de Physique de Nice, CNRS (France); Virginia D’Auria, Univ. Côte d'Azur (France), Institut de Physique de Nice, CNRS (France); Jean Etesse, Univ. Côte d’Azur (France), Institut de Physique de Nice, CNRS (France)
    5 April 2022 • 12:20 PM - 12:40 PM CEST
    Session 6: Quantum Sensing and Metrology III
    5 April 2022 • 2:00 PM - 3:40 PM CEST
    Author(s): Nigam Samantaray, Hao Yang, John Jeffers, Univ. of Strathclyde (United Kingdom)
    5 April 2022 • 2:00 PM - 2:20 PM CEST
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    Quantum lidar is a future technology aimed at using quantum states of light to achieve quantum advantage in target detection in the presence of high background noise. Although, advancement in semiconductor technology has revolutionised detector capabilities, allowing efficient detection at nearly single photon level, an efficient and successful quantum lidar requires suitable quantum states robust against noise, loss and the type of measurement. Here we consider a quantum lidar scheme which is fast in operation and based on non-simultaneous measurements, as opposed to the phase sensitive joint photon number measurement considered sometimes for quantum illumination schemes [1]. In particular, we study the multi-click heralded two mode squeezed vacuum. Multiple clicks in one mode, say the idler, force strong conditioning on the other (signal) mode, probabilistically resulting in a large relative increase in intensity of the signal state used for target detection [2]. This increase in the brightness for single clicks has been previously explored for better target detection compared with illumination using the best classical probe states [3]. Our results show, in the high loss regime, that the presence of the target is identified more quickly for multiplexed idler photodetection compared to single click heralding. We also identify a trade-off between the performance of multiplexed signal detection and the measurement speed at the receiver. We further incorporate multiple sequential shots and measurements via quantum hypothesis testing and Monte-Carlo simulation. These provide increased confidence for target determination and show significantly reduced object detection time. [1] Zhang et.al, "Entanglement-enhanced sensing in a lossy and noisy environment", Phys. Rev. Lett. 114, 110506 (2015). [2] Sperling et.al, "Quantum state engineering by click counting", Phys. Rev. A 89, 043829 (2014). [3] Yang et.al, "Gaussian state-based quantum illumination with simple photo detection", Opt. Express. 29, 8199 (2021).
    Author(s): Giacomo Sorelli, Clémentine Rouvière, Ilya Karuseichyk, David Barral, Manuel Gessner, Mattia Walschaers, Nicolas Treps, Lab. Kastler Brossel (France)
    5 April 2022 • 2:20 PM - 2:40 PM CEST
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    Resolving light sources below the diffraction limit is a fundamental task both for astronomy and microscopy. Several recent works, analysed this problem through the lens of quantum parameter estimation theory and proved that the separation between two point sources can be estimated at the quantum limit using intensity measurements after spatial-mode demultiplexing. However, most previous works have either consider low-intensity, or thermal sources. To broaden the applicability of this approach, it is important to extend these results to more general light sources. To this goal, we will present an analytical expression for the Quantum Fisher Information, determining the ultimate resolution limit, for the separation between two sources in an arbitrary Gaussian state. Applying this result to different quantum states, we can shine some light on some relevant questions. We can for example explore the role of partial coherence considering displaced and correlated thermal states, or investigate the importance of quantum correlations by considering squeezed light. In addition to the ultimate quantum limit, we will discuss a simple estimation technique, requiring access only to the mean value of a linear combination of demultiplexed intensity measurements, which is often sufficient to saturate these limits, and can easily be adapted to incorporate the most common noise sources. Finally, we will present our experimental setup that allows for the generation of the images of two sources with different photon statistics, as well as for spatial mode demultiplexing and we will discuss the first practical implementations if the above mentioned estimation techniques.
    Author(s): Alessio D'Errico, Felix Hufnagel, Seyedeh Fatemeh Dehghan Manshadi, Univ. of Ottawa (Canada); Filippo Miatto, Xanadu Quantum Technologies Inc. (Canada); Mohammadreza Rezaee, Ebrahim Karimi, Xiaoqin Gao, Univ. of Ottawa (Canada)
    5 April 2022 • 2:40 PM - 3:00 PM CEST
    Author(s): Sheng Ming, Shanghai Jiao Tong Univ. (China)
    5 April 2022 • 3:00 PM - 3:20 PM CEST
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    Lights carrying orbital angular momentum (OAM) have potential applications in precise rotation measurement, especially in remote sensing. Interferometers, especially nonlinear quantum interferometers, have also been proven to greatly improve the measurement accuracy in quantum metrology. By combining these two techniques, we theoretically propose a new atom-light hybrid Sagnac interferometer with OAM lights to advance the precision of the rotation measurement. A rotation sensitivity below standard quantum limit is achieved due to the enhancement of the quantum correlation of the interferometer even with 96% photon losses. This makes our protocol robustness to the photon loss. Furthermore, combining the slow light effect brings us at least four orders of magnitude of sensitivity better than the earth rotation rate. This new type interferometer has potential applications in high precision rotation sensing.
    Author(s): Antoine Tenart, Gaétan Hercé, Jan-Philipp Bureik, Alexandre Dareau, David Clément, Lab. Charles Fabry (France)
    5 April 2022 • 3:20 PM - 3:40 PM CEST
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    Quantum fluctuations play a central role in the properties of quantum matter. In non-interacting ensembles, they manifest as fluctuations of non-commuting observables, quantified by Heisenberg inequalities. In the presence of interactions, additional quantum fluctuations appear, from which many-body correlations and entanglement originate. In the context of many-body physics, the Bogoliubov theory provides us with an illuminating microscopic picture of how this occurs for weakly-interacting bosons, with the appearance of the quantum depletion formed by pairs of bosons with opposite momenta. This conceptually simple example yet lacks experimental confirmation. Exploiting the single particle resolution of our metastable Helium detector, we report the direct observation of pairs of atoms with opposite momenta in the depletion of an equilibrium interacting Bose gas. We show that the pair correlation signal rapidly drops as temperature rises, as expected for the quantum depletion. A quantitative study of the atom-atom correlations, both at opposite and close-by momenta, allows us to fully characterise the quantum correlations in the interacting Bose gas. Our results demonstrate how an equilibrium many-body quantum state acquires specific correlations - those of two-mode squeezed states here - as a result of the interplay between quantum fluctuations and interactions. In addition, the measured amplitudes of the correlation signals reveal sub-poissonian number differences between modes at opposite momenta, an important step towards characterising entanglement in equilibrium many-body quantum states. In the future, our approach can be used to characterize more strongly correlated systems for which a theoretical description is lacking, thus fully entering the realm of quantum simulation. - A. Tenart, G. Hercé, J.-P. Bureik, A. Dareau, D. Clément, arXiv:2105:05664 - T. D. Lee, K. Huang, and C. N. Yang, Phys. Rev. 106 (1957) - R. Lopes, C. Eigen, N. Navon, D. Clément, R. P. Smith, and Z. Hadzibabic, PRL 119 (2017) - H. Cayla, C. Carcy, Q. Bouton, R. Chang, G. Carleo, M. Mancini, and D. Clément, PRA 97 (2018) - A. Tenart, C. Carcy, H. Cayla, T. Bourdel, M. Mancini and D. Clément, PRR. 2 (2020) - H. Cayla, S. Butera, C. Carcy, A. Tenart, G. Hercé, M. Mancini, A. Aspect, I. Carusotto, and D. Clément, PRL 125 (2020)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
    Conference attendees are invited to attend the Photonics Europe poster session on Tuesday evening. Come view the posters, enjoy light refreshments, ask questions, and network with colleagues in your field.

    Poster Setup: Tuesday 10:00 AM – 5:00 PM
    View poster presentation guidelines and set-up instructions at
    Author(s): Stephen P. Najda, Piotr Perlin, Tadek Suski, Szymon Stanczyk, Mike Leszczynski, Dario Schiavon, TopGaN Ltd. (Poland); Thomas Slight, Sivers Photonics Ltd. (United Kingdom); Steffan Gwyn, Scott Watson, Anthony Kelly, Univ. of Glasgow (United Kingdom); Martin Knapp, Mohsin Haji, National Physical Lab. (United Kingdom); John Macarthur, Fraunhofer Ctr. for Applied Photonics (United Kingdom)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    GaN laser diodes have the potential to be a key enabler for many quantum technologies since the AlGaInN material system allows for laser diodes to be fabricated over a wide range of wavelengths from ultra-violet to visible. Novel applications for quantum technologies include GaN laser sources for cold-atom interferometry, such as next generation optical atomic clocks, quantum magnetometers, quantum imaging and quantum gravity sensors. GaN allows the development of very high specification laser diode sources that are portable, robust and provide practical solutions that are otherwise unobtainable using more conventional laser sources. Several approaches are taken to achieve the required linewidth, wavelength and power for cold-atom interferometry, including an extended cavity GaN laser diode (ECLD) system, and a distributed feedback (DFB) GaN laser diode with side-wall etched nano-gratings. We report our latest results on a range of AlGaInN diode-lasers targeted to meet optical atomic clock and quantum gravity sensor applications. This includes the [5s2S1/2-5p2P1/2] cooling transition in strontium+ ion optical clocks at 422 nm, the [5s21S0-5p1P1] cooling transition in neutral strontium clocks at 461 nm and the [5s2s1/2 – 6p2P3/2] transition in rubidium at 420 nm.
    Author(s): Rupesh Kumar, Univ. of York (United Kingdom); Francesco Mazzoncini, Télécom Paris (France); Hao Qin, National Univ. of Singapore (Singapore); Romain Alléaume, Télécom Paris (France)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    We have shown how to conduct QKD vulnerability assessment in practice, based on a sound methodology inherited from Common Criteria. Taking a running CV-QKD system as a reference platform, we have experimentally tested and rated two different attack paths exploiting a common threat: detector saturation. Our results illustrate the importance of rating attacks to prioritize the implementation of countermeasures and to steer the design and engineering of practical QKD systems towards the highest possible security standards, paving the way to their security certification.
    Author(s): Vyas Nilesh, Romain Alléaume, Télécom Paris (France)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    Extending the functionality and overcoming the performance limitation of QKD requires either quantum repeaters or new security models. Investigating the latter option, we introduce the Quantum Computational Timelock (QCT) security model, where we assume that computationally secure encryption may only be broken after time much longer than the coherence time of available quantum memories. Using the QCT security model, we propose an explicit d-dimensional key agreement protocol that we call MUB-Quantum Computational Timelock (MUB-QCT), where a bit is encoded on a qudit state using a full set of mutually unbiased bases (MUBs) and a family of pair-wise independent permutations. Security is proved by showing that upper bound on Eve's information scales as O(1=d). We show MUB-QCT offers: high resilience to error (up to 50% for large d) with fixed hardware requirements; MDI security as security is independent of channel monitoring and does not require to trust measurement devices. We also prove the security of the MUB-QCT protocol, with multiple photons per channel use, against non-adaptive attacks, in particular, proactive MUB measurement where eve measures each copy in a different MUB followed by post-measurement decoding. We prove that the MUB-QCT protocol allows secure key distribution with input states containing up to O(d) photons which implies a significant performance boost, characterized by an O(d) multiplication of key rate and a significant increase in the reachable distance. These results illustrate the power of the QCT security model to boost the performance of quantum cryptography while keeping a clear security advantage over classical cryptography.
    Author(s): Yujing Wang, Niels Gregersen, Luca Vannucci, Technical Univ. of Denmark (Denmark); Sven Burger, Konrad-Zuse-Zentrum für Informationstechnik Berlin (Germany), JCMwave GmbH (Germany)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
    Author(s): Yuen San Lo, Toshiba Europe Ltd. (United Kingdom)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    For the adoption of QKD to grow, increasing effort has been devoted to developing QKD systems with efficient design and robust performance. Recently, optical injection locking (OIL) has emerged as a promising technique to meet the stringent requirements placed on QKD transmitters. Not only does OIL enable the generation of phase randomized pulses at high clock rates, it can also be exploited to realise direct phase modulations for information encoding. However, tuning the laser systems is in fact a very challenging task due to its complex underlying dynamics. The difficulty arises from the number of coupled control parameters that need to be optimised simultaneously in order to achieve optimum locking condition, e.g. low noise and high coherence. It is therefore highly desirable to develop a fully autonomous optimisation approach. Here we experimentally demonstrate a self-tuning QKD transmitter by implementing a genetic algorithm (GA) to intelligently locate the optimum parameters. A GA is a type of evolutionary algorithm that mimics the process of biological evolution to explore a huge search space and effectively identify the promising solutions. Starting from an initial condition where only minimal knowledge about the laser systems is available, a GA is used to automatically tune their control parameters to minimise the quantum bit error rates (QBER) for the BB84 protocol. Without any user intervention, our GA-based optimisation method enables state of the art QKD performance to be achieved. We note that this approach is goal-oriented, therefore it can be easily applied to other QKD protocols and transmitter architecture to optimise for other properties. Further, our approach can be directly integrated into the software layer of QKD systems with no additional hardware modification required, thus representing a practical solution for current QKD systems.
    Author(s): Yuan Yao, Pierre Cussenot, Richard A. Wolf, Ecole Polytechnique (France), Télécom Paris (France); Filippo Miatto, Xanadu Quantum Technologies Inc. (Canada), Ecole Polytechnique (France), Télécom Paris (France)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    We work on the optimization task of the optical quantum circuits with continuous parameters. In order to retrieve the steepest ascent direction, we implement the Natural Gradient in the optical quantum circuit setting, adapt the NG approach to complex-valued parameter space, and compare with others.
    Author(s): John Macarthur, Jack Thomas, Fraunhofer Ctr. for Applied Photonics (United Kingdom); Stephen P. Najda, Topgan Quantum Technologies, Ltd. (United Kingdom); Shaun Jones, ALTER TECHNOLOGY TÜV NORD UK Ltd. (United Kingdom)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    Miniaturisation of laser sources is crucial to the translation of quantum technologies from the laboratory to the real world. Typically, the lasers required for cooling and trapping of atoms and ions make up a significant footprint of the measurement system. Increasing robustness and reliability whilst removing noise sources is a key challenge whilst reducing volume. Direct generation GaN based external cavity diode lasers offer lower SWaP-C compared to traditional frequency doubled alternatives. Butterfly packaged single frequency sources operation in the blue - UV allow numerous atomic transitions including Sr, Sr+, Yt, Yb+, Mg and Ca to be targeted.
    Author(s): Viviane Cotte, Rosa Tualle-Brouri, Univ. Paris-Saclay (France); Hector Simon, Univ. Paris Saclay (France)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
    Author(s): David Alvarez Outerelo, Francisco Diaz-Otero, Univ. de Vigo (Spain)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    In this work we present a Continuous variable quantum key distribution transmitter fully integrated in Indium phosphide. Passing through the design phase, layout design of the chip and the results of the measured chip. Analyzing the advantages and drawbacks of the different Photonics Integrated circuit platforms and focusing in the maximum integration level possible and the best modulation extinction ratio. A DFB Laser is integrated on the chip in order to have the maximum power available with the best linewidth possible and good single modo working point. All the integrated devices are fully reconfigurable and current controlled, for this a splitter tunable structure is designed and implemented avoiding the use of variable optical attenuators transferring the excess of power to extra outputs for monitorization. The layout of the chip is designed using Nazca that is a photonics IC design framework based in Phyton and its compatible with the building blocks of the most popular foundries. The chosen foundry is HHI the Fraunhofer Institute for Telecommunications, Hendrich Hertz Institute that have the headquarters in Berlin. The simulation of the device is done using the software VPIphotonics, using this software we run several circuital simulations characterizing the expected real behavior of the transmitter. This software allows us to use building blocks that implements mathematical models that have feedback of real devices providing us a simulating result that is the most precise if we compare this with the real behavior of the device. This is done in order to have under control fabrication issues and variations of the dielectric constant on the wafer. During the measurement phase we measure all the devices one by one characterizing them electrically and optically. Some deviations are detected from the simulations and a study of this deviations is done in order to give some answers and future design good manners new designs.
    Author(s): Tanmoy Chakraborty, Technische Univ. Delft (Netherlands); Hedser van Brug, TNO (Netherlands); Gustavo C. Amaral, Technische Univ. Delft (Netherlands), TNO (Netherlands); Anna Tchebotareva, TNO (Netherlands); Wolfgang Tittel, Technische Univ. Delft (Netherlands), Univ. de Genève (Switzerland), Schaffhausen Institute for Technology (Switzerland)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
    Author(s): Maximilian Brinkmann, Tim Hellwig, Sven Dobner, Refined Laser Systems GmbH (Germany)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    We present a novel turn-key portable fiber laser for efficient pumping of single-photon sources based on quantum dots. The laser combines a mode-hop-free and alignment-free tunability between 770nm to 980nm with a high pulse to pulse coherence of 98% visibility and more than 100mW of output power. We present long-term power stability with a standard deviation of less than 0.3% and wavelength stability of better than 5pm. We will show experimental data of generated single-photons with an excellent agreement to Ti:Sa excitation. Furthermore, we will discuss the feasibility of increasing the current pulse repetition rate of 80MHz to several hundred Megahertz and even Gigahertz, a so-far unmet demand for the scale-up of quantum hardware. This development constitutes an essential step for advancing single-photon sources based on quantum dots in terms of integrability and ease of use for research applications and quantum computing.
    Author(s): Pablo Tieben, Hiren Dobarya, Nora Bahrami, Andreas Schell, Leibniz Univ. Hannover (Germany)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    Fluorescent defect centers in hexagonal boron nitride (hBN) exhibit quantum emission with some highly favorable properties, which have made them promising candidates for integrated single photon sources during recent years. Their emission properties feature high photon count rates, narrow linewidth and long-term photostability at and above room temperature. Despite the high interest in these single photon sources, the exact level structure and their atomic origin remain elusive. By performing spectroscopic measurements, while scanning the excitation wavelength, new insight on the excited states can be extracted. Additionally, direct comparison between the photon count rates yields information about the efficiency of the involved decay channels.
    Author(s): Kerstin Thiemann, Andreas Blug, Peter Koss, Fraunhofer-Institut für Physikalische Messtechnik IPM (Germany); Ali Durmaz, Fraunhofer-Institut für Werkstoffmechanik IWM (Germany); Gennadii Laskin, Alexander Bertz, Frank Kühnemann, Fraunhofer-Institut für Physikalische Messtechnik IPM (Germany); Thomas Straub, Fraunhofer-Institut für Werkstoffmechanik IWM (Germany)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    The extreme sensitivity of quantum magnetometers enables new applications in material testing such as the identification of single defect events in the bulk of small volume specimen (1mm³). Exposing ferromagnetic materials to strain alters their magnetic response. Due to uncompensated spins, defects arising from the fatigue process interact with magnetic domain walls. Optically pumped zero-field magnetometers (OPM) provide the sensitivity required to measure small variations in the magnetic response and potentially to quantify damage in the material. We provide first results of a novel micro fatigue setup with an integrated OPM to correlate variations of the magnetic response in a multimodal approach. The position of the Villari reversals within the magneto-mechanic hysteresis and the amplitude of magnetic flied are potential candidates to estimate fatigue damage within the specimen.
    Author(s): Patrycja Tulewicz, Institute of Spintronics and Quantum Information, Adam Mickiewicz Univ. (Poland); Karol Bartkiewicz, Institute of Spintronics and Quantum Information, Adam Mickiewicz Univ. (Poland), Palacký Univ. Olomouc (Czech Republic), Institute of Physics of the CAS, v.v.i. (Czech Republic)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    One of the problems in implementing practical quantum communication networks, which we deal with, is the scalability of complex multi-user quantum communication networks [1]. The increased complexity of quantum networks and the non-cloning theorem implies the need for specialized quantum routing protocols in quantum networks [1, 2, 3]. In the search for optimal protocols and algorithms for large-scale quantum communication, the application of machine learning proves to be a powerful tools [4]. The differences in how a machine learning agent discovers protocols versus how a human invents them allows it to go beyond already known protocols and propose new protocols that are too complex to analyze manually. Our research is based on the application of machine learning tools for probabilistic operations applied within linear optics. We apply reinforcement learning [4, 5], to find the optimal routing protocols for assorted environments. The learning agent is equipped with a universal set of optical components and experimental techniques, and the target is determined by a reward function that depends on the transmission probability. The reward is granted when the probability of a successful operation is greater than an assumed level. Assuming the above approach, we study the possibility of automatically designing optimal quantum routers for an arbitrarily complex environment. Our research shows that quantum routers should be considered as versatile components possible for larger quantum networks [2]. In our optimization of quantum communications, we also accounted for the coherence of routing quantum signals between output ports for an arbitrary input state. We demonstrated that the detector performance scales only as a function of the success probability, without affecting the fidelity of the output (multi-user) state. We focus on a quantum router schemes based purely on linear-optical quantum gates [1, 2, 3], but the same circuit can be built using gates based on nonlinear optical phenomena, which provides room for development in further research ########################################################################################### References [1] Karol Bartkiewicz, Antonín Černoch, and Karel Lemr. Implementation of an efficient linear-optical quantum router. Scientific Reports, 8:2045–2322, Sep 2018. [2] Karol Bartkiewicz, Antonín Černoch, and Karel Lemr. Using quantum routers to implement quantum message authentication and bell-state manipulation. Phys. Rev. A, 90:022335, Aug 2014. [3] Karel Lemr, Karol Bartkiewicz, Antonín Černoch, and Jan Soubusta. Resource-efficient linear-optical quantum router. Phys. Rev. A, 87:062333, Jun 2013. [4] Julius Wallnöfer, Alexey A. Melnikov, Wolfgang Dür, and Hans J. Briegel. Machine learning for long-distance quantum communication. PRX Quantum, 1:010301, Sep 2020. [5] Jan Jašek, Kateřina Jiráková, Karol Bartkiewicz, Antonín Černoch, Tomáš Fürst, and Karel Lemr. Experimental hybrid quantum-classical reinforcement learning by boson sampling: how to train a quantum cloner. Opt. Express, 27(22):32454–32464, Oct 2019.
    Author(s): Shilan Abo, Ravindra Chhajlany, Grzegorz Chimczak, Anna Kowalewska-Kudlaszyk, Adam Miranowicz, Adam Mickiewicz Univ. (Poland); Franco Nori, RIKEN Ctr. for Emergent Matter Science (Japan)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    In this article we analyze a prototype opto-mechanical system realizable with, e.g., a superconducting microwave resonator (with an artificial atom), which is linearly coupled to a nanomechanical resonator. We simulate such system which can be driven into steady states, that exhibit blockade only in the combined (hybrid) photon-phonon modes, while excitation-induced tunneling occurs in the individual modes. We also predict various kinds of usual and unusual single and two-excitation blockades, which can be observed in the hybrid and individual modes by analytically choosing the system parameters as revealed by studying also higher-order excitation-number correlation functions.
    Author(s): Seyedeh Fatemeh Dehghan Manshadi, Alessio D'Errico, Xiaoqin Gao, Ebrahim Karimi, Univ. of Ottawa (Canada)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
    Author(s): Sergey A. Bogdanov, Ivan S. Sushchev, SFB Lab. Ltd. (Russian Federation), Quantum Technology Ctr., M. V. Lomonosov Moscow State Univ. (Russian Federation); Andrey N. Klimov, Quantum Technology Ctr., M. V. Lomonosov Moscow State Univ. (Russian Federation); Kirill E. Bugay, Daniil S. Bulavkin, Dmitry A. Dvoretsky, SFB Lab. Ltd. (Russian Federation), Bauman Moscow State Technical Univ. (Russian Federation)
    5 April 2022 • 6:10 PM - 8:00 PM CEST
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    Carrying out the "backflash" attack, Eve can register re-emitted photons and then determine the bit values of the secret key. Since the parameters of the pulsed laser or variable attenuator on Alice’s side and the single-photon avalanche diode (SPAD) gate duration on Bob’s side depend on the parameters of the equipment, an analysis of the backflash probabilities of photon re-emission is required to determine the optimal parameters to provide the security of the communication protocol. The SPAD gate duration was varied in the range from 0.5 to 9 ns, the mean photon number per pulse varied from 0.034 to 3.4. The obtained results demonstrate the dependencies of the backflash probabilities on the SPAD gate durations on Bob's side and on the mean photon number per pulse emitted by the pulsed laser on Alice's side.
    Session 7: Novel Quantum Platforms and Hybrid Devices I
    6 April 2022 • 9:00 AM - 10:30 AM CEST
    TBA4 (Invited Paper)
    Author(s): Anais Dreau, Technische Univ. Delft (Netherlands)
    6 April 2022 • 9:00 AM - 9:30 AM CEST
    Author(s): Julien Vaneecloo, Sébastien Garcia, Alexei Ourjoumtsev, CNRS (France), Collège de France (France)
    6 April 2022 • 9:30 AM - 9:50 AM CEST
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    We present the first building blocks for quantum engineering of light with an intracavity single Rydberg superatom. Our experimental platform is made of a small (5 μm rms) and cold (2 μK) rubidium ensemble strongly coupled to a medium-finesse running-wave resonator. The system is probed in a ladder Electromagnetically Induced Transparency (EIT) configuration to map Rydberg excitations onto photons. The van-der-Waals interactions between Rydberg atoms are converted into strong optical nonlinearities such that the propagation of photons through the cavity becomes very dependent on the Rydberg population. We experimentally verified that in our system these interactions are strong enough for the presence of one Rydberg atom to prevent the excitation of others, leading to a strong antibunching between photons transmitted through the cavity. In this regime, the atomic ensemble behaves as a single Rydberg superatom strongly coupled to the cavity. We have implemented a coherent control of this superatom via a two-photon Rabi driving between the ground and the collective singly-excited Rydberg state, observing a collective enhancement of its frequency. The state of the superatom can be optically detected via the cavity transmission with a 94% efficiency and a switching contrast of ~20. Finally, we demonstrated that our coupled system induces a 180° phase shift on the light reflected off of the cavity dependent on the superatom’s state, allowing us to detect the latter with a 90% efficiency via a homodyne measurement. This 180° phase rotation, together with the coherent control and the single-shot state detection, is a key ingredient for the implementation of an efficient controlled-phase gate or for the deterministic generation of optical “Schrödinger’s cat” states without the need for a low-volume high-finesse cavity.
    Author(s): Viktoria Yurgens, Josh A. Zuber, Sigurd Flagan, Marta De Luca, Brendan Shields, Ilaria Zardo, Patrick Maletinsky, Richard J. Warburton, Univ. Basel (Switzerland); Tomasz Jakubczyk, Univ. of Warsaw (Poland)
    6 April 2022 • 9:50 AM - 10:10 AM CEST
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    The negatively charged nitrogen-vacancy (NV) center in diamond is among the most promising solid-state systems implementations of a quantum bit. However, integration of the NV center into any efficient photonic environment requires microstructuring the diamond at below-micrometer scale. Preserving the low NV zero-phonon line inhomogeneous broadening during this process is a major challenge with standard NV creation methods. This issue severely limits practical applications of NV centers. Initial studies on pulsed-laser assisted creation of NVs yielded promising results by creating NVs with low inhomogeneous broadening at desired spatial locations in diamond [1]. Crucially, the lattice damage resulting from implantation of energetic ions was avoided. However, the method relied on a narrow window of parameters for successful writing. We widen this window by using a solid immersion lens (SIL), which facilitates laser writing over a broad range of pulse energies and allows for vacancy formation close to a diamond surface without inducing surface graphitization. We operate in the previously unexplored regime where lattice vacancies are created following tunneling breakdown rather than multiphoton ionization [2]. We present NV arrays that have been created between 1 and 40 µm from a diamond surface, all presenting optical linewidth distributions with means as low as 61.0±22.8 MHz [2], including spectral diffusion induced by off-resonant repump for charge stabilization. This emphasizes the exceptionally low charge-noise environment of laser-written NVs. Such high-quality NV centers are excellent candidates for practical applications employing two-photon quantum interference with separate NV centers. Finally, we propose a model for disentangling power broadening from inhomogeneous broadening in the NV zero-phonon line optical linewidth [2]. [1] Y.-C. Chen, P. S. Salter, S. Knauer, … and J. M. Smith, Nat. Photonics 11, 77 (2017). [2] V. Yurgens, J.A Zuber, S. Flågan, M. De Luca, B.J. Shields, I. Zardo, P. Maletinsky, R.J. Warburton, and T. Jakubczyk, ACS Photonics 8, 1726–1734 (2021)
    Author(s): Sébastien Garcia, Nicolas Vitrant, Kilian Müller, Alexei Ourjoumtsev, Collège de France, CNRS (France)
    6 April 2022 • 10:10 AM - 10:30 AM CEST
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    A high imaging resolution or a tight focus of a laser beam imposes a certain minimal numerical aperture (NA) of the optical system. Since a high NA is usually achieved by placing large lenses close to the object, one can quickly be limited by spatial constraints on the experiment. This is true, among other scenarios, when imaging or trapping cold atoms inside a vacuum chamber. Multimode fibers, in conjunction with spatial light modulators, offer an interesting alternative to the standard approach of high NA lenses. Indeed, they are flexible optical waveguides with very small transverse dimensions (~ 100 µm), and reasonably high NA (up to 0.5). For those reasons, the use of multimode fibers for imaging or laser manipulation purposes has been widely studied in the past years, especially with bio-medical applications in mind. The work we will present transfers these techniques to the field of cold atoms with a multimode fiber forming a compact optical bridge between the inside and the outside of an ultra-high vacuum chamber. We manipulate atoms with laser beams produced through the fiber by optical phase conjugation with a spatial light modulator. We are able to transport a small cloud of cold 87Rb atoms with a moving optical lattice at about 200 µm from the fiber tip. We can then load them in a small optical tweezer with a waist of 1.2 µm. By measuring interferometrically the random speckle field outputting the multimode fiber, we characterize the propagation of light modes inside the fiber. With this characterization, we reconstruct absorption images of the trapped atoms with a resolution of approximately 1 µm. This allows us to image atoms in the small tweezer and to measure their temperature.
    Session 8: Novel Quantum Platforms and Hybrid Devices II
    6 April 2022 • 11:00 AM - 12:40 PM CEST
    Author(s): Martino Bernard, Mher Ghulinyan, Fabio Acerbi, Giovanni Paternoster, Fondazione Bruno Kessler (Italy)
    6 April 2022 • 11:00 AM - 11:20 AM CEST
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    Quantum Photonic Integrated Circuits (PICs) exploit the virtually null photon-photon interaction to realize systems that are robust to external disturbance. While this resilience is particularly interesting for a development towards room-temperature systems, many experiments rely on superconducting nanowires that need cryogenic temperatures to operate. For photons in the near infrared spectral region, Single Photon Avalanche Diodes (SPADs) could be used as a room temperature alternative. We show a novel method of PIC-detector coupling that allows for the monolithic fabrication of substrate-integrated photodiodes and a silicon nitride PIC on the same chip. With the use of an engineered wet-etching process, we shape the bottom cladding of the photonic layer into a basin with shallow wedge borders on top of the region of the detectors. In this way, the waveguides are gently laid right on top of the detectors, allowing for a strong waveguide-detector optical coupling. We will show experimental results of the first PIC-diode coupling with a total efficiency exceeding 40% [Ref], and the first promising results concerning the coupling with SPADs paving the way for on-chip, room-temperature, single photon detection. Ref. Bernard, Martino, Fabio Acerbi, Giovanni Paternoster, Gioele Piccoli, Luca Gemma, Davide Brunelli, Alberto Gola, Georg Pucker, Lucio Pancheri, e Mher Ghulinyan. «Top-down Convergence of NIR Photonics with Silicon Substrate-Integrated Electronics». Optica, 16 settembre 2021. https://doi.org/10.1364/OPTICA.441496.
    Author(s): Carlo Sias, Lucia Duca, Elia Perego, Federico Berto, Naoto Mizukami, Istituto Nazionale di Ricerca Metrologica (Italy)
    6 April 2022 • 11:20 AM - 11:40 AM CEST
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    Ultracold atoms and trapped ions are among the most formidable sources of coherent matter available in a laboratory. In a hybrid quantum system of atoms and ions, ultracold atoms and trapped ions are combined in a single experimental apparatus, thus realizing an innovative platform to experimentally investigate open problems of quantum physics from a new standpoint. An atom-ion hybrid system not only brings together the advantages of each single physical system, but moreover gives rise to atom-ion interactions, which are two orders of magnitude longer-ranged than atom-atom interactions. Despite a strong interest in atom-ion experiments in recent years, atom-ion systems have not yet been brought to an s-wave scattering regime in which atoms and ions experience a long-living coherent evolution. I will report on the advancements in the realization of an experimental apparatus in which a single trapped Barium ion will be immersed into an ultracold gas of fermionic Lithium. In particular, I will report on the a number of technical advancements that we have realized in order to achieve the highest possible level of control over the atom-ion quantum mixture. These include a new ion trap for creating confining potentials for the ions with a combination of optical and electric fields [1], and a high-finesse optical cavity for confining and rapidly cool neutral atoms via unconventional sideband cooling [2]. Notably, this apparatus was recently used to successfully trap Ba+ ions, thus realizing the first ion trapping experiment in Italy. [1] E. Perego, L. Duca, C. Sias Appl. Sci. 10, 2222 (2020) [2] F. Berto, E. Perego, L. Duca, C. Sias arXiv:2107.04110 Phys. Rev. Research (in press)
    Author(s): Amirparsa Zivari, Niccolo Fiaschi, Robert Stockill, Simon Groeblacher, Technische Univ. Delft (Netherlands)
    6 April 2022 • 11:40 AM - 12:00 PM CEST
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    Quantum optics - the creation, manipulation and detection of non-classical states of light - is a fundamental cornerstone of modern physics, with many applications in basic and applied science. Achieving the same level of control over phonons, the quanta of vibrations, could have a similar impact, in particular on the fields of quantum sensing and quantum information processing. Here we demonstrate the first step towards this level of control and realize a single-mode waveguide for individual phonons in a suspended silicon micro-structure. We use a cavity-waveguide architecture, where the cavity is used as a source and detector for the mechanical excitations, while the waveguide has a free standing end in order to reflect the phonons. This enables us to observe multiple round-trips of the phonons between the source and the reflector. The long mechanical lifetime of almost 100 us demonstrates the possibility of nearly lossless transmission of single phonons over, in principle, tens of centimeters. Our experiment represents the first demonstration of full on-chip control over traveling single phonons strongly confined in the directions transverse to the propagation axis and paves the way to a time-encoded multimode quantum memory at telecom wavelength and advanced quantum acoustics experiments.
    Session 9: Quantum Components and their Applications II
    6 April 2022 • 12:00 PM - 12:40 PM CEST
    Author(s): Luisa Esguerra, Deutsches Zentrum für Luft- und Raumfahrt e.V. (Germany), Technische Univ. Berlin (Germany); Leon Messner, Deutsches Zentrum für Luft- und Raumfahrt e.V. (Germany), Institut für Physik, Humboldt-Univ. zu Berlin (Germany); Elizabeth Robertson, Deutsches Zentrum für Luft- und Raumfahrt e.V. (Germany), Institute for Optics and Atomic Physics, Technische Univ. Berlin (Germany); Mustafa Gündogan, Institut für Physik, Humboldt-Univ. zu Berlin (Germany); Janik Wolters, Deutsches Zentrum für Luft- und Raumfahrt e.V. (Germany), Institut für Optik und Atomare Physik, Technische Univ. Berlin (Germany)
    6 April 2022 • 12:00 PM - 12:20 PM CEST
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    Quantum memories are a key element for the realisation of quantum repeaters, essential for long-distance quantum communication. Especially for satellite-based quantum networks, alkali metal vapours constitute an excellent storage platform, as neither cryogenics, nor strong magnetic fields are required. We have realised a technologically simple, in principle satellite-suited quantum memory in Caesium vapor, based on electromagnetically induced transparency (EIT) on the Cs D1 line. We focus on the simultaneous optimization of end-to-end efficiency and signal-to-noise level in the memory, which will make our system suitable for many different applications. We have achieved light storage at the single-photon level with end-to-end efficiencies up to 12%, which correspond to internal memory efficiencies of up to 30%. Simultaneously we achieve a minimal noise level corresponding to µ_1=0.029 signal photons. Furthermore, we have determined the limiting noise source at this level to be four-wave mixing noise in the Lambda-system and present solutions to minimise this read-out noise.
    Author(s): Reyhaneh Ghassemizadeh, Wolfgang Körner, Daniel Urban, Fraunhofer-Institut für Werkstoffmechanik IWM (Germany); Christian Elsässer, Fraunhofer-Institut für Werkstoffmechanik IWM (Germany), Freiburg Materials Research Ctr., Univ. of Freiburg (Germany)
    6 April 2022 • 12:20 PM - 12:40 PM CEST
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    The negatively charged nitrogen-vacancy (NV) defect complex in diamond has an excellent potential for applications of quantum technologies such as quantum computing and quantum magnetometry. In this regard, its interaction and interplay with its crystal environment are of crucial importance for optimal quantum properties like long coherence times. We present a density functional theory analysis of NV centers in diamond, which are located in the vicinity of extended crystal defects, such as stacking faults and grain boundaries, or near differently oriented and terminated surfaces. We focus on the environmental influence on the electromagnetic properties of the NV center and systematically analyse their dependence on distance and relative orientation of the NV center with respect to the extended crystal defect. Our investigation reveals that there are several sites for NV centers close to extended defects which are energetically preferred with respect to the bulk crystal. This means that such defects can potentially be attractive for the NV enters. Calculating the hyperfine structure and zero-field splitting parameters of the NV centers at the extended defects, we find that the relative deviations from their bulk values are within 10%. This indicates that the influence of the extended defects on the NV centers has a short range. Moreover, we address the stability and electromagnetic properties of NV centers close to the (001) and (111) oriented surfaces and their dependencies on the H:N ratio of the surface termination. Our results indicate that NV centers with bulk-like properties are stable for distances of at least ~8Å from the surface if the surface termination contains at least 25% nitrogen atoms. Furthermore, the axial NV centers near a flat 100% N-terminated (111) surface are influenced the least by the surface and therefore are the optimal choice for NV-based quantum sensing. Our study provides insight in the interaction between NV centers and their crystallographic environments, which may be valuable in the design of NV-based applications.
    Session 10: Quantum Simulation and Computing
    6 April 2022 • 1:50 PM - 3:50 PM CEST
    TBA5 (Invited Paper)
    Author(s): Jelmer J. Renema, QuiX Quantum BV (Netherlands)
    6 April 2022 • 1:50 PM - 2:20 PM CEST
    TBA6 (Invited Paper)
    Author(s): Philipp Preiss, Ludwig-Maximilians-Univ. München (Germany)
    6 April 2022 • 2:20 PM - 2:50 PM CEST
    Author(s): Ganaël Roeland, Sorbonne Univ. (France); Ulysse Chabaud, Caltech (United States); Mattia Walschaers, Frédéric Grosshans, Valentina Parigi, Damian Markham, Nicolas Treps, Sorbonne Univ. (France)
    6 April 2022 • 2:50 PM - 3:10 PM CEST
    Author(s): Florent Baboux, Lab Matériaux et Phénomènes Quantiques, Univ. de Paris (France); Saverio Francesconi, Arnault Raymond, Nicolas Fabre, Lab. Matériaux et Phénomènes Quantiques (France); Aristide Lemaître, Ctr. de Nanosciences et de Nanotechnologies (France), CNRS (France); Perola Milman, Maria I. Amanti, Sara Ducci, Lab. Matériaux et Phénomènes Quantiques (France)
    6 April 2022 • 3:10 PM - 3:30 PM CEST
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    High-dimensional entangled states of light provide novel capabilities for quantum information, from fundamental tests of quantum mechanics to enhanced computation and communication protocols. In this context, the frequency degree of freedom is attracting a growing interest due to its robustness to propagation in optical fibers and its capability to convey large scale of quantum information into a single spatial mode. This provides a strong incentive for the development of efficient and scalable methods for the generation and manipulation of frequency-encoded quantum states. Nonlinear parametric processes are powerful tools to generate such states, but up to now the manipulation of the generated frequency states has been carried out mostly by post-manipulation, which demands complex and bulk-like experimental setups. Direct production of on-demand frequency-states at the generation stage, and preferably using a chip-based source, is crucial in view of practical and scalable applications for quantum information technologies. Here we employ parametric down-conversion in an integrated AlGaAs chip to engineer the wavefunction and exchange statistics of frequency-entangled photon pairs directly at the generation stage, without post-manipulation [1]. Tuning the pump spatial intensity allows to produce frequency-anticorrelated, correlated and separable states, while tuning the spatial phase allows to tailor the symmetry of the spectral wavefunction. As revealed by Hong-Ou-Mandel interferometry, this allows to simulate either bosons, fermions, or anyons, i.e. particles displaying a fractional exchange statistics intermediate between bosons and fermions [2]. Finally, we show that the frequency entanglement can be combined with the polarization entanglement of our source to produce hybrid frequency-polarization entangled states [3], leading to quantum beating in two-photon interference. These results, obtained at room temperature and telecom wavelength, open promising perspectives for implementing quantum simulation tasks with tailored wavefunction and particle statistics in a chip-integrated platform. [1] S. Francesconi et al, Optica 7, 316 (2020). [2] S. Francesconi et al., ACS Photonics 8, 2764 (2021). [3] S. Francesconi et al., in preparation.
    Author(s): Jannis Ehrlich, Fraunhofer-Institut für Werkstoffmechanik IWM (Germany)
    6 April 2022 • 3:30 PM - 3:50 PM CEST
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    Various functional (semi-)conductor materials used for catalysis, photovoltaics, or electrochemistry exhibit strong correlation effects due to the Coulomb interaction between their electrons, resulting in an effective competition of spatial localization versus delocalization of their electronic states. The dynamical mean field theory (DMFT) provides a proper description of this competition, as it requires the equivalence of a lattice description with an effective model, in which the strongly correlated states are described by a few fully interacting electronic modes coupled to a bath which results from all the surrounding electrons. While this approach becomes exact for an infinitely large bath, the numerical representation of a large auxiliary model is impossible on a classical computer as the Hilbert space grows exponentially with the number of electronic orbitals taken into account. In order to overcome this scaling limitation of DMFT we simulate the system on a quantum computer (QC) in such a way that each electronic mode requires one qubit. As a first application, we consider the two-site DMFT method. Following the recent work of Rungger et al., we calculate the Green's function by its Lehmann representation, which requires the energies and the preparation of the ground-state and excited-states, which we obtain by the variational quantum eigensolver (VQE) and its extensions. The QC calculations were performed in a first step with quantum simulators with and without noise, and in a second step on a real, noisy intermediate-scale quantum computer, namely the IBM Q System One. We discuss our QC results in comparison to the known analytical solution for the special case of particle-hole symmetry (half filling), and for arbitrary fillings to numerical results from exact diagonalization calculations on classical computers. The promising results show that the current limitations of classical computing in material science can be overcome by such hybrid quantum-classical computations.
    Conference Chair
    Eleni Diamanti
    CNRS, Sorbonne Univ. (France)
    Conference Chair
    Univ. Paris 7-Diderot (France)
    Conference Chair
    Lab. Kastler Brossel (France)
    Conference Chair
    Shannon Whitlock
    Univ. Strasbourg ISIS (France)
    Program Committee
    Kai Bongs
    The Univ. of Birmingham (United Kingdom)
    Program Committee
    Lab. Photonique, Numérique et Nanosciences (France)
    Program Committee
    id Quantique SA (Switzerland)
    Program Committee
    National Institute of Standards and Technology (United States)
    Program Committee
    Hugues de Riedmatten
    ICFO - Institut de Ciències Fotòniques (Spain)
    Program Committee
    Chiara Macchiavello
    Univ. degli Studi di Pavia (Italy)
    Program Committee
    Tracy E. Northup
    Univ. Innsbruck (Austria)
    Program Committee
    Sapienza Univ. di Roma (Italy)
    Program Committee
    Paolo Villoresi
    Univ. degli Studi di Padova (Italy)
    Program Committee
    Univ. des Saarlandes (Germany)
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