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  • 1. Assali, S.
    et al.
    Laehnemann, J.
    Vu, T. T. T.
    Jöns, Klaus
    Delft University of Technology, Netherlands.
    Gagliano, L.
    Verheijen, M. A.
    Akopian, N.
    Bakkers, E. P. A. M.
    Haverkort, J. E. M.
    Crystal Phase Quantum Well Emission with Digital Control2017In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 10, p. 6062-6068Article in journal (Refereed)
    Abstract [en]

    One of the major challenges in the growth of quantum well and quantum dot heterostructures is the realization of atomically sharp interfaces. Nanowires provide a new opportunity to engineer the band structure as they facilitate the controlled switching of the crystal structure between the zinc-blende (ZB) and wurtzite (WZ) phases. Such a crystal phase switching results in the formation of crystal phase quantum wells (CPQWs) and quantum dots (CPQDs). For GaP CPQWs, the inherent electric fields due to the discontinuity of the spontaneous polarization at the WZ/ZB junctions lead to the confinement of both types of charge carriers at the opposite interfaces of the WZ/ZB/WZ structure. This confinement leads to a novel type of transition across a ZB flat plate barrier. Here, we show digital tuning of the visible emission of WZ/ZB/WZ CPQWs in a GaP nanowire by changing the thickness of the ZB barrier. The energy spacing between the sharp emission lines is uniform and is defined by the addition of single ZB monolayers. The controlled growth of identical quantum wells with atomically flat interfaces at predefined positions featuring digitally tunable discrete emission energies may provide a new route to further advance entangled photons in solid state quantum systems.

  • 2.
    Basset, F. Basso
    et al.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Rota, M. B.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Schimpf, C.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Tedeschi, D.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Zeuner, Katharina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    da Silva, S. F. Covre
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Reindl, M.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Rastelli, A.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Trotta, R.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Entanglement Swapping with Photons Generated on Demand by a Quantum Dot2019In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 123, no 16, article id 160501Article in journal (Refereed)
    Abstract [en]

    Photonic entanglement swapping, the procedure of entangling photons without any direct interaction, is a fundamental test of quantum mechanics and an essential resource to the realization of quantum networks. Probabilistic sources of nonclassical light were used for seminal demonstration of entanglement swapping, but applications in quantum technologies demand push-button operation requiring single quantum emitters. This, however, turned out to be an extraordinary challenge due to the stringent prerequisites on the efficiency and purity of the generation of entangled states. Here we show a proof-of-concept demonstration of all-photonic entanglement swapping with pairs of polarization-entangled photons generated on demand by a GaAs quantum dot without spectral and temporal filtering. Moreover, we develop a theoretical model that quantitatively reproduces the experimental data and provides insights on the critical figures of merit for the performance of the swapping operation. Our theoretical analysis also indicates how to improve stateof-the-art entangled-photon sources to meet the requirements needed for implementation of quantum dots in long-distance quantum communication protocols.

  • 3.
    Basso Basset, F.
    et al.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Salusti, F.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Rota, M. B.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Tedeschi, D.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Covre da Silva, S. F.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Roccia, E.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Paderborn Univ, Dept Phys, D-33098 Paderborn, Germany..
    Rastelli, A.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Trotta, R.
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Quantum teleportation with imperfect quantum dots2021In: NPJ QUANTUM INFORMATION, ISSN 2056-6387, Vol. 7, no 1, article id 7Article in journal (Refereed)
    Abstract [en]

    Efficient all-photonic quantum teleportation requires fast and deterministic sources of highly indistinguishable and entangled photons. Solid-state-based quantum emitters-notably semiconductor quantum dots-are a promising candidate for the role. However, despite the remarkable progress in nanofabrication, proof-of-concept demonstrations of quantum teleportation have highlighted that imperfections of the emitter still place a major roadblock in the way of applications. Here, rather than focusing on source optimization strategies, we deal with imperfections and study different teleportation protocols with the goal of identifying the one with maximal teleportation fidelity. Using a quantum dot with sub-par values of entanglement and photon indistinguishability, we show that the average teleportation fidelity can be raised from below the classical limit to 0.842(14), adopting a polarization-selective Bell state measurement and moderate spectral filtering. Our results, which are backed by a theoretical model that quantitatively explains the experimental findings, loosen the very stringent requirements set on the ideal entangled-photon source and highlight that imperfect quantum dots can still have a say in teleportation-based quantum communication architectures.

  • 4.
    Elshaari, Ali W.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Buyukozer, Efe
    Swiss Fed Inst Technol, Dept Mech & Proc Engn, CH-8092 Zurich, Switzerland..
    Zadeh, Iman Esmaeil
    Delft Univ Technol, Opt Grp, NL-2628 CJ Delft, Netherlands..
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zhao, Peng
    Tsinghua Univ, Tsinghua Natl Lab Informat Sci & Technol, Dept Elect Engn, Beijing, Peoples R China..
    Schöll, Eva
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Reimer, Michael E.
    Univ Waterloo, Inst Quantum Comp, Waterloo, ON N2L 3G1, Canada.;Univ Waterloo, Dept Elect & Comp Engn, Waterloo, ON N2L 3G1, Canada..
    Dalacu, Dan
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Poole, Philip J.
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Strain-Tunable Quantum Integrated Photonics2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 12, p. 7969-7976Article in journal (Refereed)
    Abstract [en]

    Semiconductor quantum dots are crucial parts of the photonic quantum technology toolbox because they show excellent single-photon emission properties in addition to their potential as solid-state qubits. Recently, there has been an increasing effort to deterministically integrate single semiconductor quantum dots into complex photonic circuits. Despite rapid progress in the field, it remains challenging to manipulate the optical properties of waveguide-integrated quantum emitters in a deterministic, reversible, and nonintrusive manner. Here we demonstrate a new class of hybrid quantum photonic circuits combining III V semiconductors, silicon nitride, and piezoelectric crystals. Using a combination of bottom-up, top-down, and nanomanipulation techniques, we realize strain tuning of a selected, waveguide-integrated, quantum emitter and a planar integrated optical resonator. Our findings are an important step toward realizing reconfigurable quantum-integrated photonics, with full control over the quantum sources and the photonic circuit.

  • 5.
    Elshaari, Ali W.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Esmaeil Zadeh, I.
    Fognini, A.
    Dalacu, D.
    Poole, P. J.
    Reimer, M. E.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Hybrid quantum photonic integrated circuits2018In: Proceedings - International Conference Laser Optics 2018, ICLO 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, article id 8435508Conference paper (Refereed)
    Abstract [en]

    Quantum photonic integrated circuits require a scalable approach to integrate bright on-demand sources of entangled photon-pairs in complex on-chip quantum photonic circuits. Currently, the most promising sources are based on III/V semiconductor quantum dots. However, complex photonic circuitry is mainly achieved in silicon photonics due to the tremendous technological challenges in circuit fabrication. We take the best of both worlds by developing a new hybrid on-chip nanofabrication approach, allowing to integrate III/V semiconductor nanowire quantum emitters into silicon-based photonics.

  • 6.
    Elshaari, Ali W.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zadeh, I. E.
    Fognini, A.
    Reimer, M. E.
    Dalacu, D.
    Poole, P. J.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Jöns, Klaus
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Hybrid quantum photonics2017In: Optics InfoBase Conference Papers, Optical Society of America, 2017, Vol. Part F43Conference paper (Refereed)
    Abstract [en]

    We deterministically integrate nanowire quantum-emitters in SiN photonic circuits. We generate single-photons, suppress excitation-laser, and isolate specific transitions in the quantumemitter all on-chip with electrically-tunable filter. Finally, we demonstrate a novel Quantum- WDM channel on-chip.

  • 7.
    Elshaari, Ali W.
    et al.
    KTH, School of Electrical Engineering (EES).
    Zadeh, Iman Esmaeil
    Fognini, Andreas
    Reimer, Michael E.
    Dalacu, Dan
    Poole, Philip J.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, School of Electrical Engineering (EES).
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics.
    On-chip single photon filtering and multiplexing in hybrid quantum photonic circuits2017In: Nature Communications, E-ISSN 2041-1723, Vol. 8, article id 379Article in journal (Refereed)
    Abstract [en]

    Quantum light plays a pivotal role in modern science and future photonic applications. Since the advent of integrated quantum nanophotonics different material platforms based on III-V nanostructures-, colour centers-, and nonlinear waveguides as on-chip light sources have been investigated. Each platform has unique advantages and limitations; however, all implementations face major challenges with filtering of individual quantum states, scalable integration, deterministic multiplexing of selected quantum emitters, and on-chip excitation suppression. Here we overcome all of these challenges with a hybrid and scalable approach, where single III-V quantum emitters are positioned and deterministically integrated in a complementary metal-oxide-semiconductor-compatible photonic circuit. We demonstrate reconfigurable on-chip single-photon filtering and wavelength division multiplexing with a foot print one million times smaller than similar table-top approaches, while offering excitation suppression of more than 95 dB and efficient routing of single photons over a bandwidth of 40 nm. Our work marks an important step to harvest quantum optical technologies' full potential.

  • 8.
    Elshaari, Ali W.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO. Delft Univ Technol, Kavli Inst Nanosci, Netherlands.
    Zadeh, Iman Esmaeil
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO. Delft Univ Technol, Kavli Inst Nanosci, Netherlands.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Thermo-Optic Characterization of Silicon Nitride Resonators for Cryogenic Photonic Circuits2016In: IEEE Photonics Journal, E-ISSN 1943-0655, Vol. 8, no 3, article id 2701009Article in journal (Refereed)
    Abstract [en]

    In this paper, we characterize the Thermo-optic properties of silicon nitride ring resonators between 18 and 300 K. The Thermo-optic coefficients of the silicon nitride core and the oxide cladding are measured by studying the temperature dependence of the resonance wavelengths. The resonant modes show low temperature dependence at cryogenic temperatures and higher dependence as the temperature increases. We find the Thermo-optic coefficients of PECVD silicon nitride and silicon oxide to be 2.51 +/- 0.08 E-5 K-1 and 0.96 +/- 0.09 E-5 K-1 at room temperature while decreasing by an order of magnitude when cooling to 18 K. To show the effect of variations in the thermo-optic coefficients on device performance, we study the tuning of a fully integrated electrically tunable filter as a function of voltage for different temperatures. The presented results provide new practical guidelines in designing photonic circuits for studying low-temperature optical phenomena.

  • 9.
    Errando-Herranz, Carlos
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    Schöll, Eva
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Picard, Raphael
    Heriot Watt Univ, Inst Photon & Quantum Sci, SUPA, Edinburgh EH14 4AS, Midlothian, Scotland..
    Laini, Micaela
    Heriot Watt Univ, Inst Photon & Quantum Sci, SUPA, Edinburgh EH14 4AS, Midlothian, Scotland..
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Elshaari, Ali W.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Branny, Artur
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Wennberg, Ulrika
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Barbat, Sebastien
    Renaud, Thibaut
    Sartison, Marc
    Paderborn Univ, Dept Phys, D-33098 Paderborn, Germany..
    Brotons-Gisbert, Mauro
    Heriot Watt Univ, Inst Photon & Quantum Sci, SUPA, Edinburgh EH14 4AS, Midlothian, Scotland..
    Bonato, Cristian
    Heriot Watt Univ, Inst Photon & Quantum Sci, SUPA, Edinburgh EH14 4AS, Midlothian, Scotland..
    Gerardot, Brian D.
    Heriot Watt Univ, Inst Photon & Quantum Sci, SUPA, Edinburgh EH14 4AS, Midlothian, Scotland..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Resonance Fluorescence from Waveguide-Coupled, Strain-Localized, Two-Dimensional Quantum Emitters2021In: ACS Photonics, E-ISSN 2330-4022, Vol. 8, no 4, p. 1069-1076Article in journal (Refereed)
    Abstract [en]

    Efficient on-chip integration of single-photon emitters imposes a major bottleneck for applications of photonic integrated circuits in quantum technologies. Resonantly excited solid-state emitters are emerging as near-optimal quantum light sources, if not for the lack of scalability of current devices. Current integration approaches rely on cost-inefficient individual emitter placement in photonic integrated circuits, rendering applications impossible. A promising scalable platform is based on two-dimensional (2D) semiconductors. However, resonant excitation and single-photon emission of waveguide-coupled 2D emitters have proven to be elusive. Here, we show a scalable approach using a silicon nitride photonic waveguide to simultaneously strain-localize single-photon emitters from a tungsten diselenide (WSe2) monolayer and to couple them into a waveguide mode. We demonstrate the guiding of single photons in the photonic circuit by measuring second-order autocorrelation of g((2))(0) = 0.150 +/- 0.093 and perform on-chip resonant excitation, yielding a g((2))(0) = 0.377 +/- 0.081. Our results are an important step to enable coherent control of quantum states and multiplexing of high-quality single photons in a scalable photonic quantum circuit.

  • 10.
    Fognini, A.
    et al.
    Delft Univ Technol, Kavli Inst Nanosci Delft, NL-2628 CJ Delft, Netherlands. hmadi, A..
    Ahmadi, A.
    Zeeshan, M.
    Fokkens, J. T.
    Gibson, S. J.
    Sherlekar, N.
    Daley, S. J.
    Dalacu, D.
    Poole, P. J.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reimer, M. E.
    Dephasing Free Photon Entanglement with a Quantum Dot2019In: ACS Photonics, E-ISSN 2330-4022, Vol. 6, no 7, p. 1656-1663Article in journal (Refereed)
    Abstract [en]

    Generation of photon pairs from quantum dots with near-unity entanglement fidelity has been a long-standing scientific challenge. It is generally thought that the nuclear spins limit the entanglement fidelity through spin flip dephasing processes. However, this assumption lacks experimental support. Here, we show two-photon entanglement with negligible dephasing from an indium rich single quantum dot comprising a nuclear spin of 9/2 when excited quasi-resonantly. This finding is based on a significantly close match between our entanglement measurements and our model that assumes no dephasing and takes into account the detection system's timing jitter and dark counts. We suggest that neglecting the detection system is responsible for the degradation of the measured entanglement fidelity in the past and not the nuclear spins. Therefore, the key to unity entanglement from quantum dots comprises a resonant excitation scheme and a detection system with ultralow timing jitter and dark counts.

  • 11.
    Gyger, Samuel
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zeuner, Katharina D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Elshaari, Ali W.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Paul, Matthias
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Reuterskiöld Hedlund, Carl
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Hammar, Mattias
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Ozolins, Oskars
    KTH, School of Engineering Sciences (SCI), Applied Physics. Rise AB, NETLAB, Isafjordsgatan 22, S-16440 Kista, Sweden.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Reconfigurable frequency coding of triggered single photons in the telecom C-band2019In: Optics Express, E-ISSN 1094-4087, Vol. 27, no 10, p. 14400-14406Article in journal (Refereed)
    Abstract [en]

    In this work, we demonstrate reconfigurable frequency manipulation of quantum states of light in the telecom C-band. Triggered single photons are encoded in a superposition state of three channels using sidebands up to 53 GHz created by an off-the-shelf phase modulator. The single photons are emitted by an InAs/GaAs quantum dot grown by metal-organic vapor-phase epitaxy within the transparency window of the backbone fiber optical network. A cross-correlation measurement of the sidebands demonstrates the preservation of the single photon nature; an important prerequisite for future quantum technology applications using the existing telecommunication fiber network.

  • 12.
    Gyger, Samuel
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Elshaari, Ali W.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Covre da Silva, S. F.
    Johannes Kepler Universität, Linz, Austria.
    Rastelli, A.
    Johannes Kepler Universität, Linz, Austria.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Errando-Herranz, Carlos
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    On-chip integration of reconfigurable quantum photonics with superconducting photodetectors2021In: Optics InfoBase Conference Papers, The Optical Society , 2021Conference paper (Refereed)
    Abstract [en]

    Scaling up quantum optics experiments requires on-chip reconfigurable quantum photonics, but their integration with detectors is a challenge. We show microelectromechanical reconfiguration of photonic circuits with on-chip superconducting single-photon detectors and demonstrate key applications.

  • 13.
    Gyger, Samuel
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Elshaari, Ali W.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Da Silva, S. F. C.
    Rastelli, A.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Errando-Herranz, Carlos
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    On-chip integration of reconfigurable quantum photonics with superconducting photodetectors2021In: 2021 Conference on Lasers and Electro-Optics, CLEO 2021 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2021Conference paper (Refereed)
    Abstract [en]

    Scaling up quantum optics experiments requires on-chip reconfigurable quantum photonics, but their integration with detectors is a challenge. We show microelectrome-chanical reconfiguration of photonic circuits with on-chip superconducting single-photon detectors and demonstrate key applications. 

  • 14.
    Gyger, Samuel
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. KTH Royal Inst Technol, Dept Appl Phys, Stockholm, Sweden..
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Elshaari, Ali W.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    da Silva, Saimon F. Covre
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, Linz, Austria..
    Rastelli, Armando
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, Linz, Austria..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Errando-Herranz, Carlos
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    Reconfigurable photonics with on-chip single-photon detectors2021In: Nature Communications, E-ISSN 2041-1723, Vol. 12, no 1, article id 1408Article in journal (Refereed)
    Abstract [en]

    Integrated quantum photonics offers a promising path to scale up quantum optics experiments by miniaturizing and stabilizing complex laboratory setups. Central elements of quantum integrated photonics are quantum emitters, memories, detectors, and reconfigurable photonic circuits. In particular, integrated detectors not only offer optical readout but, when interfaced with reconfigurable circuits, allow feedback and adaptive control, crucial for deterministic quantum teleportation, training of neural networks, and stabilization of complex circuits. However, the heat generated by thermally reconfigurable photonics is incompatible with heat-sensitive superconducting single-photon detectors, and thus their on-chip co-integration remains elusive. Here we show low-power microelectromechanical reconfiguration of integrated photonic circuits interfaced with superconducting single-photon detectors on the same chip. We demonstrate three key functionalities for photonic quantum technologies: 28 dB high-extinction routing of classical and quantum light, 90 dB high-dynamic range single-photon detection, and stabilization of optical excitation over 12 dB power variation. Our platform enables heat-load free reconfigurable linear optics and adaptive control, critical for quantum state preparation and quantum logic in large-scale quantum photonics applications. Integrated photonics are promising to scale up quantum optics. Here the authors combine low-power microelectromechanical control and superconducting single-photon detectors on the same chip and demonstrate routing, high-dynamic-range detection, and power stabilization.

  • 15.
    Haffouz, Sofiane
    et al.
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Zeuner, Katharina D.
    KTH.
    Dalacu, Dan
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Poole, Philip J.
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Lapointe, Jean
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Poitras, Daniel
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Mnaymneh, Khaled
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Wu, Xiaohua
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Couillard, Martin
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Korkusinski, Marek
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Schöll, Eva
    KTH.
    Jöns, Klaus D.
    KTH.
    Zwiller, Valery
    KTH.
    Williams, Robin L.
    Natl Res Council Canada, Ottawa, ON K1A 0R6, Canada..
    Bright Single InAsP Quantum Dots at Telecom Wavelengths in Position-Controlled InP Nanowires: The Role of the Photonic Waveguide2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 5, p. 3047-3052Article in journal (Refereed)
    Abstract [en]

    We report on the site-selected growth of bright single InAsP quantum dots embedded within InP photonic nanowire waveguides emitting at telecom wavelengths. We demonstrate a dramatic dependence of the emission rate on both the emission wavelength and the nanowire diameter. With an appropriately designed waveguide, tailored to the emission wavelength of the dot, an increase in the count rate by nearly 2 orders of magnitude (0.4 to 35 kcps) is obtained for quantum dots emitting in the telecom O-band, showing high single-photon purity with multiphoton emission probabilities down to 2%. Using emission-wavelength-optimized waveguides, we demonstrate bright, narrow-line-width emission from single InAsP quantum dots with an unprecedented tuning range of 880 to 1550 nm. These results pave the way toward efficient single-photon sources at telecom wavelengths using deterministically grown InAsP/InP nanowire quantum dots.

  • 16.
    Hanschke, Lukas
    et al.
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Dept Elect & Comp Engn, D-85748 Garching, Germany.;Munich Ctr Quantum Sci & Technol MCQST, D-80799 Munich, Germany..
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Carreno, Juan Camilo Lopez
    Univ Wolverhampton, Fac Sci & Engn, Wulfruna St, Wolverhampton WV1 1LY, England..
    Schöll, Eva
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zeuner, Katharina D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Casalengua, Eduardo Zubizarreta
    Univ Wolverhampton, Fac Sci & Engn, Wulfruna St, Wolverhampton WV1 1LY, England..
    Reindl, Marcus
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    da Silva, Saimon Filipe Covre
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Trotta, Rinaldo
    Sapienza Univ Roma, Dipartimento Fis, Piazzale A Moro 1, I-00185 Rome, Italy..
    Finley, Jonathan J.
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Munich Ctr Quantum Sci & Technol MCQST, D-80799 Munich, Germany.;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany..
    Rastelli, Armando
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    del Valle, Elena
    Univ Wolverhampton, Fac Sci & Engn, Wulfruna St, Wolverhampton WV1 1LY, England.;Univ Autonoma Madrid, Dept Fis Teor Mat Condensada, Madrid 28049, Spain..
    Laussy, Fabrice P.
    Univ Wolverhampton, Fac Sci & Engn, Wulfruna St, Wolverhampton WV1 1LY, England.;Russian Quantum Ctr, Novaya 100, Skolkovo 143025, Moscow Region, Russia..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Muller, Kai
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Dept Elect & Comp Engn, D-85748 Garching, Germany.;Munich Ctr Quantum Sci & Technol MCQST, D-80799 Munich, Germany..
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics. Albanova Univ Ctr, Royal Paderborn Univ, Dept Phys, D-33098 Paderborn, Germany..
    Origin of Antibunching in Resonance Fluorescence2020In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 125, no 17, article id 170402Article in journal (Refereed)
    Abstract [en]

    Resonance fluorescence has played a major role in quantum optics with predictions and later experimental confirmation of nonclassical features of its emitted light such as antibunching or squeezing. In the Rayleigh regime where most of the light originates from the scattering of photons with subnatural linewidth, antibunching would appear to coexist with sharp spectral lines. Here, we demonstrate that this simultaneous observation of subnatural linewidth and antibunching is not possible with simple resonant excitation. Using an epitaxial quantum dot for the two-level system, we independently confirm the single-photon character and subnatural linewidth by demonstrating antibunching in a Hanbury Brown and Twiss type setup and using high-resolution spectroscopy, respectively. However, when filtering the coherently scattered photons with filter bandwidths on the order of the homogeneous linewidth of the excited state of the two-level system, the antibunching dip vanishes in the correlation measurement. Our observation is explained by antibunching originating from photon-interferences between the coherent scattering and a weak incoherent signal in a skewed squeezed state. This prefigures schemes to achieve simultaneous subnatural linewidth and antibunched emission.

  • 17. Hanschke, Lukas
    et al.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Lopez~Carreño, Juan Camilo
    Zeuner, Katharina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schöll, Eva
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zubizarreta Casalengua, Eduardo
    Reindl, Marcus
    Covre da Silva, Saimon Filipe
    Trotta, Rinaldo
    Finley, Jonathan J.
    Rastelli, Armando
    del Valle, Elena
    Laussy, Fabrice P.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Müller, Kai
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Coherent scattering: either sub-natural linewidth or anti-bunched lightManuscript (preprint) (Other academic)
    Abstract [en]

    Epitaxial quantum dots have emerged as one of the best single–photon sources, not only for applications in photonic quantum technologies but also for testing fundamental properties of quantum optics. One intriguing observation in this area is the emission of photons with subnatural–linewidth from a two-level system under resonant continuous wave excitation. In particular, an open question is whether these subnatural–linewidth photons exhibit simultaneously single–photon characteristics, i.e. show antibunching as a signature of single-photon emission. Here, we demonstrate that this simultaneous observation of subnatural–linewidth and single photoncharacter is not possible with simple resonant excitation. First, we independently confirm single–photon character and subnatural–linewidth by demonstrating antibunching in a Hanbury Brown and Twiss type setup and using high-resolution spectroscopy, respectively. However, when filtering the coherently scattered photons with filter bandwidths on the order of the homogeneous linewidth of the excited state of the two-level system, the antibunching dip vanishes in the correlation measurement. Our experimental work is consistent with recent theoretical findings, and can be explained by a fundamental model considering higher-order photon correlations.

  • 18. Hoetger, Alexander
    et al.
    Klein, Julian
    Barthelmi, Katja
    Sigl, Lukas
    Sigger, Florian
    Manner, Wolfgang
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Florian, Matthias
    Lorke, Michael
    Jahnke, Frank
    Taniguchi, Takashi
    Watanabe, Kenji
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Wurstbauer, Ursula
    Kastl, Christoph
    Mueller, Kai
    Finley, Jonathan J.
    Holleitner, Alexander W.
    Gate-Switchable Arrays of Quantum Light Emitters in Contacted Monolayer MoS2 van der Waals Heterodevices2021In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 21, no 2, p. 1040-1046Article in journal (Refereed)
    Abstract [en]

    We demonstrate electrostatic switching of individual, site-selectively generated matrices of single photon emitters (SPEs) in MoS2 van der Waals heterodevices. We contact monolayers of MoS2 in field-effect devices with graphene gates and hexagonal boron nitride as the dielectric and graphite as bottom gates. After the assembly of such gate-tunable heterodevices, we demonstrate how arrays of defects, that serve as quantum emitters, can be site-selectively generated in the monolayer MoS2 by focused helium ion irradiation. The SPEs are sensitive to the charge carrier concentration in the MoS2 and switch on and off similar to the neutral exciton in MoS2 for moderate electron doping. The demonstrated scheme is a first step for producing scalable, gate-addressable, and gate-switchable arrays of quantum light emitters in MoS2 heterostacks.

  • 19.
    Jöns, Klaus D.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Versteegh, Marijn A. M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Dalacu, D.
    Poole, P. J.
    Gulinatti, A.
    Giudice, A.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reimer, M. E.
    Erratum to: Bright nanoscale source of deterministic entangled photon pairs violating Bell’s inequality (Scientific Reports, (2017), 7, 1, (1700), 10.1038/s41598-017-01509-6)2017In: Scientific Reports, E-ISSN 2045-2322, Vol. 7, no 1, article id 7751Article in journal (Refereed)
  • 20.
    Jöns, Klaus D.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics. Delft University of Technology, Netherlands.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics. Delft University of Technology, Netherlands.
    Versteegh, Marijn A. M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics. Delft University of Technology, Netherlands.
    Dalacu, Dan
    Poole, Philip J.
    Gulinatti, Angelo
    Giudice, Andrea
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics. Delft University of Technology, Netherlands.
    Reimer, Michael E.
    Bright nanoscale source of deterministic entangled photon pairs violating Bell's inequality2017In: Scientific Reports, E-ISSN 2045-2322, Vol. 7, no 1, article id 1700Article in journal (Refereed)
    Abstract [en]

    Global, secure quantum channels will require efficient distribution of entangled photons. Long distance, low-loss interconnects can only be realized using photons as quantum information carriers. However, a quantum light source combining both high qubit fidelity and on-demand bright emission has proven elusive. Here, we show a bright photonic nanostructure generating polarization-entangled photon pairs that strongly violates Bell's inequality. A highly symmetric InAsP quantum dot generating entangled photons is encapsulated in a tapered nanowire waveguide to ensure directional emission and efficient light extraction. We collect similar to 200 kHz entangled photon pairs at the first lens under 80 MHz pulsed excitation, which is a 20 times enhancement as compared to a bare quantum dot without a photonic nanostructure. The performed Bell test using the Clauser-Horne-Shimony-Holt inequality reveals a clear violation (S-CHSH > 2) by up to 9.3 standard deviations. By using a novel quasi-resonant excitation scheme at the wurtzite InP nanowire resonance to reduce multi-photon emission, the entanglement fidelity (F = 0.817 +/- 0.002) is further enhanced without temporal post-selection, allowing for the violation of Bell's inequality in the rectilinear-circular basis by 25 standard deviations. Our results on nanowire-based quantum light sources highlight their potential application in secure data communication utilizing measurement-device-independent quantum key distribution and quantum repeater protocols.

  • 21.
    Jöns, Klaus D.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. AlbaNova University Center.
    Stensson, Katarina
    KTH, School of Engineering Sciences (SCI), Applied Physics. AlbaNova University Center.
    Reindl, Marcus
    Swillo, Marcin
    KTH, School of Engineering Sciences (SCI), Applied Physics. AlbaNova University Center.
    Huo, Yongheng
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics. AlbaNova University Center.
    Rastelli, Armando
    Trotta, Rinaldo
    Björk, Gunnar
    KTH, School of Engineering Sciences (SCI), Applied Physics. AlbaNova University Center.
    Two-photon interference from two blinking quantum emitters2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 7, article id 075430Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of blinking on the two-photon interference measurement from two independent quantum emitters. We find that blinking significantly alters the statistics in the Hong-Ou-Mandel second-order intensity correlation function g((2))(tau) and the outcome of two-photon interference measurements performed with independent quantum emitters. We theoretically demonstrate that the presence of blinking can be experimentally recognized by a deviation from the g(D)((2))(0) = 0.5 value when distinguishable photons from two emitters impinge on a beam splitter. Our findings explain the significant differences between linear losses and blinking for correlation measurements between independent sources and are experimentally verified using a parametric down-conversion photon-pair source. We show that blinking imposes a mandatory cross-check measurement to correctly estimate the degree of indistinguishability of photons emitted by independent quantum emitters.

  • 22. Klein, Julian
    et al.
    Sigl, Lukas
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Barthelmi, Katja
    Florian, Matthias
    Rey, Sergio
    Taniguchi, Takashi
    Watanabe, Kenji
    Jahnke, Frank
    Kastl, Christoph
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Mueller, Kai
    Wurstbauer, Ursula
    Finley, Jonathan J.
    Holleitner, Alexander W.
    Engineering the Luminescence and Generation of Individual Defect Emitters in Atomically Thin MoS22021In: ACS Photonics, E-ISSN 2330-4022, Vol. 8, no 2, p. 669-677Article in journal (Refereed)
    Abstract [en]

    We demonstrate the on-demand creation and positioning of photon emitters in atomically thin MoS2 with very narrow ensemble broadening and negligible background luminescence. Focused helium-ion beam irradiation creates 100s to 1000s of such mono-typical emitters at specific positions in the MoS2 monolayers. Individually measured photon emitters show anti-bunching behavior with a g(2)(0) similar to 0.23 and 0.27. From a statistical analysis, we extract the creation yield of the He-ion induced photon emitters in MoS2 as a function of the exposed area, as well as the total yield of single emitters as a function of the number of He ions when single spots are irradiated by He ions. We reach probabilities as high as 18% for the generation of individual and spectrally clean photon emitters per irradiated single site. Our results firmly establish 2D materials as a platform for photon emitters with unprecedented control of position as well as photophysical properties owing to the all-interfacial nature.

  • 23.
    Leandro, Lorenzo
    et al.
    Tech Univ Denmark, DTU Dept Photon Engn, DK-2800 Lyngby, Denmark..
    Gunnarsson, Christine P.
    Tech Univ Denmark, DTU Dept Photon Engn, DK-2800 Lyngby, Denmark..
    Reznik, Rodion
    St Petersburg Acad Univ, RAS, St Petersburg 194021, Russia.;ITMO Univ, Kronverkskiy Pr 49, St Petersburg 197101, Russia..
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Shtrom, Igor
    St Petersburg Acad Univ, RAS, St Petersburg 194021, Russia..
    Khrebtov, Artem
    ITMO Univ, Kronverkskiy Pr 49, St Petersburg 197101, Russia..
    Kasama, Takeshi
    Tech Univ Denmark, DTU Dept Photon Engn, DK-2800 Lyngby, Denmark..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics. Delft Univ Technol, Kavli Inst Nanosci, NL-2628CJ Delft, Netherlands..
    Cirlin, George
    St Petersburg Acad Univ, RAS, St Petersburg 194021, Russia.;ITMO Univ, Kronverkskiy Pr 49, St Petersburg 197101, Russia..
    Akopian, Nika
    Tech Univ Denmark, DTU Dept Photon Engn, DK-2800 Lyngby, Denmark..
    Nanowire Quantum Dots Tuned to Atomic Resonances2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 11, p. 7217-7221Article in journal (Refereed)
    Abstract [en]

    Quantum dots tuned to atomic resonances represent an emerging field of hybrid quantum systems where the advantages of quantum dots and natural atoms can be combined. Embedding quantum dots in nanowires boosts these systems with a set of powerful possibilities, such as precise positioning of the emitters, excellent photon extraction efficiency and direct electrical contacting of quantum dots. Notably, nanowire structures can be grown on silicon substrates, allowing for a straightforward integration with silicon-based photonic devices. In this work we show controlled growth of nanowire-quantum-dot structures on silicon, frequency tuned to atomic transitions. We grow GaAs quantum dots in AlGaAs nanowires with a nearly pure crystal structure and excellent optical properties. We precisely control the dimensions of quantum dots and their position inside nanowires and demonstrate that the emission wavelength can be engineered over the range of at least 30 nm around 765 nm. By applying an external magnetic field, we are able to fine-tune the emission frequency of our nanowire quantum dots to the D-2 transition of Rb-87. We use the Rb transitions to precisely measure the actual spectral line width of the photons emitted from a nanowire quantum dot to be 9.4 +/- 0.7 mu eV, under nonresonant excitation. Our work brings highly desirable functionalities to quantum technologies, enabling, for instance, a realization of a quantum network, based on an arbitrary number of nanowire single-photon sources, all operating at the same frequency of an atomic transition.

  • 24.
    Lettner, Thomas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zeuner, Katharina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reuterskiöld-Hedlund, Carl
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Stroj, Sandra
    Vorarlberg Univ Appl Sci, Res Ctr Microtechnol, A-6850 Dornbirn, Austria..
    Rastelli, Armando
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Hammar, Mattias
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Trotta, Rinaldo
    Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Paderborn Univ, Inst Photon Quantum Syst PhoQS, Ctr Optoelect & Photon Paderborn CeOPP, D-33098 Paderborn, Germany.;Paderborn Univ, Dept Phys, D-33098 Paderborn, Germany..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Strain-Controlled Quantum Dot Fine Structure for Entangled Photon Generation at 1550 nm2021In: Nano Letters, ISSN 1530-6984, E-ISSN 1530-6992, Vol. 21, no 24, p. 10501-10506Article in journal (Refereed)
    Abstract [en]

    Entangled photon generation at 1550 nm in the telecom C-band is of critical importance as it enables the realization of quantum communication protocols over long distance using deployed telecommunication infrastructure. InAs epitaxial quantum dots have recently enabled on-demand generation of entangled photons in this wavelength range. However, time-dependent state evolution, caused by the fine-structure splitting, currently limits the fidelity to a specific entangled state. Here, we show fine-structure suppression for InAs quantum dots using micromachined piezoelectric actuators and demonstrate generation of highly entangled photons at 1550 nm. At the lowest fine-structure setting, we obtain a maximum fidelity of 90.0 +/- 2.7% (concurrence of 87.5 +/- 3.1%). The concurrence remains high also for moderate (weak) temporal filtering, with values close to 80% (50%), corresponding to 30% (80%) of collected photons, respectively. The presented fine-structure control opens the way for exploiting entangled photons from quantum dots in fiber-based quantum communication protocols.

  • 25.
    Lettner, Thomas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zeuner, Katharina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reuterskiöld-Hedlund, Carl
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Stroj, Sandra
    Rastelli, Armando
    Hammar, Mattias
    KTH, Superseded Departments (pre-2005), Microelectronics and Information Technology, IMIT. KTH, Superseded Departments (pre-2005), Electronics. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Trotta, Rinaldo
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Strain-controlled quantum dot fine-structure for entangled-photon generation at 1550 nmManuscript (preprint) (Other academic)
    Abstract [en]

    Entangled-photon generation at 1550nm in the telecom C-band is of critical importance, since it enables the realization of quantum communication protocols over long distance using deployed telecommunication infrastructure. InAs epitaxial quantum dots have recently enabled on-demand generation of entangled pairs of photons in this wavelength range. However, time-dependent state evolution, caused by the fine-structure splitting, currently limits the fidelity to a specific entangled state. Here, we show suppression of the fine-structure for InAs quantum dots using micromachined piezoelectric actuators and demonstrate generation of highly entangled photons in the telecom C-band. At the lowest fine-structure setting, we obtain a maximum fidelity of (90.0 ± 2.7)% (concurrence of (87.5 ± 3.1)%). The concurrence remains high also for moderate (weak) temporal-filtering, with values close to 80% (50%), corresponding to 30% (80%) of collected photons, respectively. The presented fine-structure control opens the way for the exploitation of entangled photons from quantum dots in fiber-based quantum communication protocols.

  • 26.
    Lettner, Thomas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zeuner, Katharina D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Schöll, Eva
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Huang, Huiying
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Scharmer, Selim
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    da Silva, Saimon Filipe Covre
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Rastelli, Armando
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    GaAs Quantum Dot in a Parabolic Microcavity Tuned to Rb-87 D-12020In: ACS Photonics, E-ISSN 2330-4022, Vol. 7, no 1, p. 29-35Article in journal (Refereed)
    Abstract [en]

    We develop a structure to efficiently extract photons emitted by a GaAs quantum dot tuned to rubidium. For this, we employ a broadband microcavity with a curved gold backside mirror that we fabricate by a combination of photoresist reflow, dry reactive ion etching in an inductively coupled plasma, and selective wet chemical etching. Precise reflow and etching control allows us to achieve a parabolic backside mirror with a short focal distance of 265 nm. The fabricated structures yield a predicted (measured) collection efficiency of 63% (12%), an improvement by more than 1 order of magnitude compared to unprocessed samples. We then integrate our quantum dot parabolic microcavities onto a piezoelectric substrate capable of inducing a large in-plane biaxial strain. With this approach, we tune the emission wavelength by 0.5 nm/kV, in a dynamic, reversible, and linear way, to the rubidium D-1 line (795 nm).

  • 27. Lin, Zuzeng
    et al.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Efficient toolbox for correlation of time tagged measurementsManuscript (preprint) (Other academic)
    Abstract [en]

    Extracting correlations from time-series data is a wide-spread analysing method for large data sets, giving insights in temporal dynamics over several orders ofmagnitudes. However, the efficient correlation extraction and processing of big data is still a challenge widely encountered, independent of the application and research field. In optics, correlations among photon detection events can often yield insight into underlying physical processes. The recent advent of time-tagging techniques for photon detection events with timing resolution compa-rable to the coherence and lifetimes of quantum emitters offers an alternative to the well established start-stop histograms obtained directly with correlation electronics. Here we introduce a versatile toolbox for analysis of time tagged data, enabling extraction of a wide range of information from one measurement. A user of our software can specify the desired analysis method using a combination of graphical and traditional programming. Automatically selecting an appropriate algorithm, a just-in-time compiler combines these two inputs into an intermediate representation, which is then compiled into assembly code optimized for the target computer’s architecture. This procedure optimizes for fast analysis of large time tag files at the cost of upfront compilation time while maintaining flexibility. Our program finds uses in single molecule, LIDAR, quantum entanglement and fluorescence correlation spectroscopy measurements, as well as quantum key distribution protocols in which data from remote detectors needs to be synchronized and correlated. Our software is optimized and modular, offering high processing speed and extensibility.

  • 28. Orieux, Adeline
    et al.
    Versteegh, Marijn A. M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics.
    Ducci, Sara
    Semiconductor devices for entangled photon pair generation: a review2017In: Reports on progress in physics (Print), ISSN 0034-4885, E-ISSN 1361-6633, Vol. 80, no 7, article id 076001Article, review/survey (Refereed)
    Abstract [en]

    Entanglement is one of the most fascinating properties of quantum mechanical systems; when two particles are entangled the measurement of the properties of one of the two allows the properties of the other to be instantaneously known, whatever the distance separating them. In parallel with fundamental research on the foundations of quantum mechanics performed on complex experimental set-ups, we assist today with bourgeoning of quantum information technologies bound to exploit entanglement for a large variety of applications such as secure communications, metrology and computation. Among the different physical systems under investigation, those involving photonic components are likely to play a central role and in this context semiconductor materials exhibit a huge potential in terms of integration of several quantum components in miniature chips. In this article we review the recent progress in the development of semiconductor devices emitting entangled photons. We will present the physical processes allowing the generation of entanglement and the tools to characterize it; we will give an overview of major recent results of the last few years and highlight perspectives for future developments.

  • 29.
    Reindl, Marcus
    et al.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Huber, Daniel
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Schimpf, Christian
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    da Silva, Saimon F. Covre
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Rota, Michele B.
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria.;Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    Huang, Huiying
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Rastelli, Armando
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria.;Johannes Kepler Univ Linz, Linz Inst Technol, A-4040 Linz, Austria..
    Trotta, Rinaldo
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria.;Sapienza Univ Rome, Dept Phys, I-00185 Rome, Italy..
    All-photonic quantum teleportation using on-demand solid-state quantum emitters2018In: Science Advances, E-ISSN 2375-2548, Vol. 4, no 12, article id eaau1255Article in journal (Refereed)
    Abstract [en]

    All-optical quantum teleportation lies at the heart of quantum communication science and technology. This quantum phenomenon is built up around the nonlocal properties of entangled states of light that, in the perspective of real-life applications, should be encoded on photon pairs generated on demand. Despite recent advances, however, the exploitation of deterministic quantum light sources in push-button quantum teleportation schemes remains a major open challenge. Here, we perform an important step toward this goal and show that photon pairs generated on demand by a GaAs quantum dot can be used to implement a teleportation protocol whose fidelity violates the classical limit (by more than 5 SDs) for arbitrary input states. Moreover, we develop a theoretical framework that matches the experimental observations and that defines the degree of entanglement and indistinguishability needed to overcome the classical limit independently of the input state. Our results emphasize that on-demand solid-state quantum emitters are one of the most promising candidates to realize deterministic quantum teleportation in practical quantum networks.

  • 30. Reindl, Marcus
    et al.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics.
    Huber, Daniel
    Schimpf, Christian
    Huo, Yongheng
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, School of Electrical Engineering (EES).
    Rastelli, Armando
    Trotta, Rinaldo
    Phonon-Assisted Two-Photon Interference from Remote Quantum Emitters2017In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 7, p. 4090-4095Article in journal (Refereed)
    Abstract [en]

    Photonic quantum technologies are on the verge of finding applications in everyday life with quantum cryptography and quantum simulators on the horizon. Extensive research has been carried out to identify suitable quantum emitters and single epitaxial quantum dots have emerged as near-optimal sources of bright, on demand, highly indistinguishable single photons and entangled photon-pairs. In order to build up quantum networks, it is essential to interface remote quantum emitters. However, this is still an outstanding challenge, as the quantum states of dissimilar "artificial atoms" have to be prepared on-demand with high fidelity and the generated photons have to be made indistinguishable in all possible degrees of freedom. Here, we overcome this major obstacle and show an unprecedented two-photon interference (visibility of 51 +/- 5%) from remote strain-tunable GaAs quantum dots emitting on-demand photon-pairs. We achieve this result by exploiting for the first time the full potential of a novel phonon-assisted two-photon excitation scheme, which allows for the generation of highly indistinguishable (visibility of 71 +/- 9%) entangled photon-pairs (fidelity of 90 +/- 2%), enables push-button biexciton state preparation (fidelity of 80 +/- 2%) and outperforms conventional resonant two-photon excitation schemes in terms of robustness against environmental decoherence. Our results mark an important milestone for the practical realization of quantum repeaters and complex multiphoton entanglement experiments involving dissimilar artificial atoms.

  • 31.
    Schweickert, Lucas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zeuner, Katharina
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Elshaari, Ali W.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Fognini, A.
    Zadeh, I. E.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Generating, manipulating and detecting quantum states of light at the nanoscale2018In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2018Conference paper (Refereed)
    Abstract [en]

    We generate, manipulate and detect light at the single photon level with semiconducting and superconducting nanowires.

  • 32.
    Schweickert, Lucas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zeuner, Katharina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    da Silva, Saimon Filipe Covre
    Huang, Huiying
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reindl, Marcus
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Trotta, Rinaldo
    Rastelli, Armando
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    On-demand generation of background-free single photons from a solid-state source2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 9, article id 093106Article in journal (Refereed)
    Abstract [en]

    True on-demand high-repetition-rate single-photon sources are highly sought after for quantum information processing applications. However, any coherently driven two-level quantum system suffers from a finite re-excitation probability under pulsed excitation, causing undesirable multi-photon emission. Here, we present a solid-state source of on-demand single photons yielding a raw second-order coherence of g((2)) (0) = (7.5 +/- 1.6) x 10(-5) without any background subtraction or data processing. To this date, this is the lowest value of g((2)) (0) Peported for any single-photon source even compared to the previously reported best background subtracted values. We achieve this result on GaAs/AlGaAs quantum dots embedded in a low-Q planar cavity by employing (i) a two-photon excitation process and (ii) a filtering and detection setup featuring two superconducting single-photon detectors with ultralow dark-count rates of (0.0056 +/- 0.0007) s(-1) and (0.017 +/- 0.001) s(-1), respectively. Re-excitation processes are dramatically suppressed by (i), while (ii) removes false coincidences resulting in a negligibly low noise floor.

  • 33.
    Schöll, Eva
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hanschke, Lukas
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany..
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zeuner, Katharina D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reindl, Marcus
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    da Silva, Saimon Filipe Covre
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Trotta, Rinaldo
    Sapienza Univ Roma, Dipartimento Fis, Piazzale A Moro 1, I-00185 Rome, Italy..
    Finley, Jonathan J.
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany..
    Mueller, Kai
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany..
    Rastelli, Armando
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Resonance Fluorescence of GaAs Quantum Dots with Near-Unity Photon Indistinguishability2019In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 19, no 4, p. 2404-2410Article in journal (Refereed)
    Abstract [en]

    Photonic quantum technologies call for scalable quantum light sources that can be integrated, while providing the end user with single and entangled photons on demand. One promising candidate is strain free GaAs/A1GaAs quantum dots obtained by aluminum droplet etching. Such quantum dots exhibit ultra low multi-photon probability and an unprecedented degree of photon pair entanglement. However, different to commonly studied InGaAs/GaAs quantum dots obtained by the Stranski-Krastanow mode, photons with a near-unity indistinguishability from these quantum emitters have proven to be elusive so far. Here, we show on-demand generation of near-unity indistinguishable photons from these quantum emitters by exploring pulsed resonance fluorescence. Given the short intrinsic lifetime of excitons and trions confined in the GaAs quantum dots, we show single photon indistinguishability with a raw visibility of V-raw = (95.0(-6.1)(+5.0))%, without the need for Purcell enhancement. Our results represent a milestone in the advance of GaAs quantum dots by demonstrating the final missing property standing in the way of using these emitters as a key component in quantum communication applications, e.g., as quantum light sources for quantum repeater architectures.

  • 34.
    Schöll, Eva
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Paderborn Univ, Dept Phys, D-33098 Paderborn, Germany..
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hanschke, Lukas
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Dept Elect & Comp Engn, D-85748 Garching, Germany.;Munich Ctr Quantum Sci & Technol, Schellingstr 4, D-80799 Munich, Germany..
    Zeuner, Katharina D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Sbresny, Friedrich
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Dept Elect & Comp Engn, D-85748 Garching, Germany.;Munich Ctr Quantum Sci & Technol, Schellingstr 4, D-80799 Munich, Germany..
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Trivedi, Rahul
    Stanford Univ, Ginzton Lab, Stanford, CA 94305 USA..
    Reindl, Marcus
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    da Silva, Saimon Filipe Covre
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Trotta, Rinaldo
    Sapienza Univ Roma, Dipartimento Fis, Piazzale A Moro 1, I-00185 Rome, Italy..
    Finley, Jonathan J.
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Munich Ctr Quantum Sci & Technol, Schellingstr 4, D-80799 Munich, Germany.;Tech Univ Munich, Phys Dept, D-85748 Garching, Germany..
    Vuckovic, Jelena
    Stanford Univ, Ginzton Lab, Stanford, CA 94305 USA..
    Mueller, Kai
    Tech Univ Munich, Walter Schottky Inst, D-85748 Garching, Germany.;Tech Univ Munich, Dept Elect & Comp Engn, D-85748 Garching, Germany.;Munich Ctr Quantum Sci & Technol, Schellingstr 4, D-80799 Munich, Germany..
    Rastelli, Armando
    Johannes Kepler Univ Linz, Inst Semicond & Solid State Phys, A-4040 Linz, Austria..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Paderborn Univ, Dept Phys, D-33098 Paderborn, Germany..
    Crux of Using the Cascaded Emission of a Three-Level Quantum Ladder System to Generate Indistinguishable Photons2020In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 125, no 23, article id 233605Article in journal (Refereed)
    Abstract [en]

    We investigate the degree of indistinguishability of cascaded photons emitted from a three-level quantum ladder system; in our case the biexciton-exciton cascade of semiconductor quantum dots. For the three-level quantum ladder system we theoretically demonstrate that the indistinguishability is inherently limited for both emitted photons and determined by the ratio of the lifetimes of the excited and intermediate states. We experimentally confirm this finding by comparing the quantum interference visibility of noncascaded emission and cascaded emission from the same semiconductor quantum dot. Quantum optical simulations produce very good agreement with the measurements and allow us to explore a large parameter space. Based on our model, we propose photonic structures to optimize the lifetime ratio and overcome the limited indistinguishability of cascaded photon emission from a three-level quantum ladder system.

  • 35.
    Schöll, Eva
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hanschke, Lukas
    Zeuner, Katharina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Sbresny, Friedrich
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Trivedi, Rahul
    Reindl, Marcus
    Covre da Silva, Saimon Filipe
    Trotta, Rinaldo
    Finley, Jonathan J.
    Vuckovic, Jelena
    Müller, Kai
    Rastelli, Armando
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    The crux of using the cascaded emission of a 3-level quantum ladder system to generate indistinguishable photonsManuscript (preprint) (Other academic)
    Abstract [en]

    We investigate the degree of indistinguishability of cascaded photons emitted from a 3–level quantum ladder system; in our case the biexciton–exciton cascade of semiconductor quantum dots. For the 3–level quantum ladder system we theoretically demonstrate that the indistinguishability is inherently limited for both emitted photons and determined by the ratio of the lifetimes of the excited and intermediate states. We experimentally confirm this finding by comparing the quantum interference visibility of non–cascaded emission and cascaded emission from the same semiconductor quantum dot. Quantum optical simulations produce very good agreement with the measurements and allow to explore a large parameter space. Based on our model, we propose photonic structures too ptimize the lifetime ratio and overcome the limited indistinguishability of cascaded photon emission from a 3–level quantum ladder system.

  • 36.
    Steinhauer, Stephan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Yang, Lily
    KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Errando-Herranz, Carlos
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Baghban, Mohammad Amin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Gallo, Katia
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    NbTiN thin films for superconducting photon detectors on photonic and two-dimensional materials2020In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118Article in journal (Refereed)
    Abstract [en]

    Integration of superconducting devices on photonic platforms opens up a wide range of functionalities and applications. We report on NbTiN thin films deposited on SiO2, Si3N4, GaAs, LiNbO3, and AlN as well as on a monolayer of hexagonal boron nitride, using a universal reactive co-sputtering recipe. The morphology and the superconducting properties of the NbTiN thin films with a thickness of 10 nm were characterized by atomic force microscopy and electrical transport measurements. Superconducting strip photon detectors were fabricated using a design suitable for waveguide integration and compared in terms of their internal quantum efficiency and detection pulse kinetics. Our results show well-comparable performances for detectors integrated on different platforms, while also demonstrating that reactive co-sputter deposition of NbTiN at room temperature provides a robust method for realizing superconducting devices on various materials.Superconducting materials are the fundamental building block for a wide variety of devices such as Josephson junctions, magnetic field probes, and electromagnetic radiation detectors. Moreover, they form a platform for quantum computing as well as neuromorphic circuit architectures. To utilize the full potential of superconducting thin films and take advantage of their versatile functionalities, fabrication processes suitable for integration on different platforms are required. For instance, superconducting strip photon detectors1 (SSPDs; nomenclature according to the International Standard IEC is used,2 whereas in the literature, these devices are also referred to as superconducting nanowire single-photon detectors) have been demonstrated with different thin film systems on multiple substrate materials and have evolved into the leading technology for single-photon detection.3,4 They offer a wide wavelength sensitivity range,5 high detection efficiency, low dark count rate, and high time resolution6–9 and can be integrated on waveguides in photonic integrated circuits.10 However, integration of SSPDs is often complicated by application-specific restrictions and dedicated growth processes using high temperatures or intermediate buffer layers. While amorphous materials such as WSi are associated with high detection efficiencies and a forgiving fabrication process resulting in a good detector fabrication yield,11 it is challenging to achieve low timing jitter12 and detector operation typically requires sub-Kelvin temperatures. On the other hand, the nitride-based superconductors NbN and NbTiN excel in time resolution but are less forgiving in terms of fabrication yield due to their nanocrystalline structure, often requiring deposition at elevated temperatures.In this Letter, we show the integration of NbTiN-based SSPD devices on photonic and monolayer two-dimensional materials using a universal reactive co-sputtering process at room temperature. Six substrate materials were studied: silicon dioxide (SiO2), silicon nitride (Si3N4), gallium arsenide (GaAs), lithium niobate (LiNbO3), aluminum nitride (AlN), and hexagonal boron nitride (hBN). SiO2 is commonly used for the fabrication of free-space or fiber-coupled SSPDs due to the refractive index difference between SiO2 and the Si substrate underneath forming a weak optical cavity.13 Si3N4 is a CMOS-compatible material that offers a wide transparency window from the visible to the mid-infrared and is suitable for efficient photonic waveguiding. SSPDs can be integrated either before Si3N4 growth as embedded detectors14 or on top of the photonic circuit.15 AlN is used as a piezo-electric material, for instance, in resonators, transducers, and actuators. Superconducting detectors were also fabricated using a pick and place technique16 and by NbN deposition at high temperatures.17 LiNbO3 as an optically non-linear material with a large transparency window and electro-optical properties allows for second-harmonic generation and electro-optic modulation. SSPDs were demonstrated on planar substrates,18,19 whereas superconducting transition-edge sensors were realized on titanium in-diffused waveguides.20 GaAs is a common photonic platform that also allows for the fabrication of quantum dot-based non-classical light sources. The integration of NbN SSPDs requires precise control of deposition temperature to preserve the substrate integrity21–23 or the use of a buffer layer.24 Finally, two-dimensional crystals and van der Waals heterostructures have emerged as optoelectronic platforms with unique characteristics.25 hBN, in particular, is an important building block that is used as a dielectric, for passivation or for its optical properties in the ultraviolet range.26 However, SSPDs realized on two-dimensional crystals as substrate material have remained unexplored so far.We realized NbTiN thin films by reactive co-sputtering from separate Nb and Ti targets at room temperature. We developed a universal recipe for the deposition of 10 nm NbTiN on all six material platforms without substrate-dependent adaptation. The deposition rate and nominal film thickness were monitored in situ using a rate monitor calibrated for SiO2/Si substrates (uncertainty 5%). The magnetron sources were operated at a DC bias of 120 W and a RF bias of 240 W for Nb and Ti, respectively, using an Ar/N2 ratio of 10 and a sputtering pressure of 3 mTorr. These deposition conditions result in polycrystalline films with a Nb/Ti ratio around 60% suitable for high-efficiency SSPDs with a sub-20 ps timing jitter, as reported previously for SiO2/Si substrates.27 The following samples were used: thin film SiO2 on Si (150 nm thermal oxide), thin film Si3N4 on SiO2/Si (250 nm low pressure chemical vapor deposition; Rogue Valley Microdevices), bulk GaAs wafer (Wafer Technology); bulk LiNbO3 wafer (x-cut; CasTech), thin film AlN on Si (200 nm plasma vapor deposition; Kyma Technologies), and monolayer hBN on SiO2/Si (chemical vapor deposition growth and PMMA transfer, oxide thickness 285 nm; Graphene Supermarket). Measurements of NbTiN step heights by atomic force microscopy in tapping mode suggested well-comparable thicknesses for films on SiO2 compared to Si3N4, GaAs, LiNbO3, and AlN with relative differences below 4% (hBN was excluded from the step height analysis due to surface irregularities resulting from the transfer process). Furthermore, the surface morphology of all substrates was assessed (Fig. 1), characterizing areas with NbTiN as well as bare substrate areas covered during the deposition. The root mean square surface roughness Rq was extracted and is summarized for all the cases in Table I. Sputtering of 10 nm NbTiN at room temperature had a negligible influence on the surface roughness, confirming the homogeneity of film deposition. Low Rq values of 0.3–0.6 nm were found for SiO2, Si3N4, and GaAs, whereas larger values were measured for LiNbO3 (0.9 nm), hBN (1.0 nm), and AlN (1.2 nm). In the latter case of AlN, the surface roughness was determined by its distinct grain morphology [Fig. 1(e)]. Note that for the monolayer hBN substrate, circular surface irregularities were present, which were excluded from the roughness analysis.

  • 37. Tedeschi, D
    et al.
    Basso Basset, F
    Rota, M B
    Schimpf, C
    Reindl, M
    Huber, D
    Zeuner, Katharina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    da Silva, S F C
    Huang, H
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Rastelli, A
    Trotta, R
    All-photonic quantum teleportation and entanglement swapping using on-demand solid-state quantum emitters2019In: Quantum Information and Measurement, QIM 2019, OSA - The Optical Society , 2019, Vol. Part F165-Conference paper (Refereed)
    Abstract [en]

    Quantum teleportation and entanglement swapping represent pivot concepts in quantum information science. Here, we show that entangled photon pairs generated on-demand by quantum-dots can be used to implement successfully quantum teleportation and entanglement swapping protocols. 

  • 38.
    Tuktamyshev, A.
    et al.
    Univ Milano Bicocca, L NESS, Via R Cozzi 55, I-20125 Milan, Italy.;Univ Milano Bicocca, Mat Sci Dept, Via R Cozzi 55, I-20125 Milan, Italy..
    Fedorov, A.
    L NESS, Via F Anzani 42, I-22100 Como, Italy.;CNR, IFN, Polo Como, Via F Anzani 42, I-22100 Como, Italy..
    Bietti, S.
    Univ Milano Bicocca, L NESS, Via R Cozzi 55, I-20125 Milan, Italy.;Univ Milano Bicocca, Mat Sci Dept, Via R Cozzi 55, I-20125 Milan, Italy..
    Vichi, S.
    Univ Milano Bicocca, L NESS, Via R Cozzi 55, I-20125 Milan, Italy.;Univ Milano Bicocca, Mat Sci Dept, Via R Cozzi 55, I-20125 Milan, Italy..
    Zeuner, Katharina
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Chrastina, D.
    L NESS, Via F Anzani 42, I-22100 Como, Italy.;Politecn Milan, Polo Como, Phys Dept, Via F Anzani 42, I-22100 Como, Italy..
    Tsukamoto, S.
    Univ Milano Bicocca, L NESS, Via R Cozzi 55, I-20125 Milan, Italy.;Univ Milano Bicocca, Mat Sci Dept, Via R Cozzi 55, I-20125 Milan, Italy..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Gurioli, M.
    Univ Firenze, Phys & Astron Dept, Via G Sansone 1, I-50019 Sesto Fiorentino, Italy..
    Sanguinetti, S.
    Univ Milano Bicocca, L NESS, Via R Cozzi 55, I-20125 Milan, Italy.;Univ Milano Bicocca, Mat Sci Dept, Via R Cozzi 55, I-20125 Milan, Italy..
    Telecom-wavelength InAs QDs with low fine structure splitting grown by droplet epitaxy on GaAs(111)A vicinal substrates2021In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 118, no 13, article id 133102Article in journal (Refereed)
    Abstract [en]

    We present self-assembly of InAs/InAlAs quantum dots by the droplet epitaxy technique on vicinal GaAs(111)A substrates. The small miscut angle, while maintaining the symmetries imposed on the quantum dot from the surface, allows a fast growth rate thanks to the presence of preferential nucleation sites at the step edges. A 100nm InAlAs metamorphic layer with In content >= 50% directly deposited on the GaAs substrate is already almost fully relaxed with a very flat surface. The quantum dots emit at the 1.3 mu m telecom O-band with fine structure splitting as low as 16 mu eV, thus making them suitable as photon sources in quantum communication networks using entangled photons.

  • 39. Wang, Y.
    et al.
    Pelgrin, V.
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Lafforgue, C.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Department of Physics, Paderborn University, Paderborn, 33098, Germany.
    Cassan, E.
    Sun, Z.
    Heterogeneous silicon nitride waveguide integrated with few-layer WS2 for on-chip nonlinear optics2021In: Optics InfoBase Conference Papers, Optica Publishing Group , 2021Conference paper (Refereed)
  • 40.
    Wang, Yuchen
    et al.
    Aalto Univ, Dept Elect & Nanoengn, POB 13500, Aalto, Finland..
    Pelgrin, Vincent
    Aalto Univ, Dept Elect & Nanoengn, POB 13500, Aalto, Finland.;Univ Paris Saclay, Ctr Nanosci & Nanotechnol, CNRS, F-91120 Palaiseau, France..
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Lafforgue, Christian
    Univ Paris Saclay, Ctr Nanosci & Nanotechnol, CNRS, F-91120 Palaiseau, France..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Paderborn Univ, Dept Phys, D-33098 Paderborn, Germany..
    Cassan, Eric
    Univ Paris Saclay, Ctr Nanosci & Nanotechnol, CNRS, F-91120 Palaiseau, France..
    Sun, Zhipei
    Aalto Univ, Dept Elect & Nanoengn, POB 13500, Aalto, Finland.;Aalto Univ, QTF Ctr Excellence, Dept Appl Phys, FI-00076 Aalto, Finland..
    Heterogeneous silicon nitride waveguide integrated with few-layer WS2 for on-chip nonlinear optics2021In: 2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), Institute of Electrical and Electronics Engineers (IEEE) , 2021Conference paper (Refereed)
    Abstract [en]

    Recently, two-dimensional materials have attracted significant interests for nonlinear optics [1] . Here, we report on the experimental investigation and the numerical modelling of nonlinear pulse propagation in a heterogeneous silicon nitride channel waveguide with the integration of a few-layer WS 2 flake significantly increasing the effective nonlinearity.

  • 41.
    Zadeh, I. E.
    et al.
    Optics Group, Delft University of Technology, Delft, Netherlands.
    Elshaari, Ali W.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Los, J. W. N.
    cSingle Quantum B.V., Delft, Netherlands.
    Gourgues, R.
    cSingle Quantum B.V., Delft, Netherlands.
    Zichi, J.
    cSingle Quantum B.V., Delft, Netherlands.
    Dorenbos, S.
    cSingle Quantum B.V., Delft, Netherlands.
    Reimer, M. E.
    cSingle Quantum B.V., Delft, Netherlands.
    Dalacu, D.
    cSingle Quantum B.V., Delft, Netherlands.
    Poole, P. J.
    cSingle Quantum B.V., Delft, Netherlands.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. cSingle Quantum B.V., Delft, Netherlands.
    Zwiller, V.
    cSingle Quantum B.V., Delft, Netherlands.
    Pereira, S.
    Optics Group, Delft University of Technology, Delft, Netherlands.
    Scalable quantum optics with nanowires2019In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2019Conference paper (Refereed)
    Abstract [en]

    Single-photon generation, processing, and detection are the three main components of any quantum optical circuit. We present our results on integration of semiconducting nanowire quantum dots, dielectric waveguides, and ultrahigh performance superconducting nanowire single-photon detectors.

  • 42. Zadeh, Iman Esmaeil
    et al.
    Elshaari, Ali W.
    KTH, School of Electrical Engineering (EES). Delft Univ Technol, Netherlands.
    Jöns, Klaus D.
    KTH, School of Electrical Engineering (EES). Delft Univ Technol, Netherlands.
    Fognini, Andreas
    Dalacu, Dan
    Poole, Philip J.
    Reimer, Michael E.
    Zwiller, Val
    KTH, School of Electrical Engineering (EES). Delft Univ Technol, Netherlands.
    Deterministic Integration of Single Photon Sources in Silicon Based Photonic Circuits2016In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 16, no 4, p. 2289-2294Article in journal (Refereed)
    Abstract [en]

    A major step toward fully integrated quantum optics is the deterministic incorporation of high quality single photon sources in on-chip optical circuits. We show a novel hybrid approach in which preselected III-V single quantum dots in nanowires are transferred and integrated in silicon based photonic circuits. The quantum emitters maintain their high optical quality after integration as verified by measuring a low multiphoton probability of 0.07 +/- 0.07 and emission line width as narrow as 3.45 +/- 0.48 GHz. Our approach allows for optimum alignment of the quantum dot light emission to the fundamental waveguide mode resulting in very high coupling efficiencies. We estimate a coupling efficiency of 24.3 +/- 1.7% from the studied single-photon source to the photonic channel and further show by finite-difference time-domain simulations that for an optimized choice of material and design the efficiency can exceed 90%.

  • 43.
    Zeuner, Katharina D.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Paul, Matthias
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Reuterskiold Hedlund, Carl
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Yang, Lily
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zichi, Julien
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Hammar, Mattias
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    A stable wavelength-tunable triggered source of single photons and cascaded photon pairs at the telecom C-band2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 17, article id 173102Article in journal (Refereed)
    Abstract [en]

    The implementation of fiber-based long-range quantum communication requires tunable sources of single photons at the telecom C-band. Stable and easy-to-implement wavelength-tunability of individual sources is crucial to (i) bring remote sources into resonance, (ii) define a wavelength standard, and (iii) ensure scalability to operate a quantum repeater. So far, the most promising sources for true, telecom single photons are semiconductor quantum dots, due to their ability to deterministically and reliably emit single and entangled photons. However, the required wavelength-tunability is hard to attain. Here, we show a stable wavelength-tunable quantum light source by integrating strain-released InAs quantum dots on piezoelectric substrates. We present triggered single-photon emission at 1.55 mu m with a multi-photon emission probability as low as 0.097, as well as photon pair emission from the radiative biexciton-exciton cascade. We achieve a tuning range of 0.25 nm which will allow us to spectrally overlap remote quantum dots or tuning distant quantum dots into resonance with quantum memories. This opens up realistic avenues for the implementation of photonic quantum information processing applications at telecom wavelengths. 

  • 44.
    Zeuner, Katharina
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Reuterskiöld-Hedlund, Carl
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Nunez Lobato, Carlos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Wang, Kai
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schöll, Eva
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hammar, Mattias
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    On-Demand Generation of Entangled Photon Pairs in the Telecom C-Band with InAs Quantum Dots2021In: ACS Photonics, E-ISSN 2330-4022, Vol. 8, no 8, p. 2337-2344Article in journal (Refereed)
    Abstract [en]

    Entangled photons are an integral part in quantum optics experiments and a key resource in quantum imaging, quantum communication, and photonic quantum information processing. Making this resource available on-demand has been an ongoing scientific challenge with enormous progress in recent years. Of particular interest is the potential to transmit quantum information over long distances, making photons the only reliable flying qubit. Entangled photons at the telecom C-band could be directly launched into single-mode optical fibers, enabling worldwide quantum communication via existing telecommunication infrastructure. However, the on-demand generation of entangled photons at this desired wavelength window has been elusive. Here, we show a photon pair generation efficiency of 69.9 +/- 3.6% in the telecom C-band by an InAs/GaAs semiconductor quantum dot on a metamorphic buffer layer. Using a robust phonon-assisted two-photon excitation scheme we measure a maximum concurrence of 91.4 +/- 3.8% and a peak fidelity to the Phi(+) state of 95.2 +/- 1.1%, verifying on-demand generation of strongly entangled photon pairs and marking an important milestone for interfacing quantum light sources with our classical fiber networks.

  • 45.
    Zeuner, Katharina
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schweickert, Lucas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics.
    Reuterskiöld-Hedlund, Carl
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Nuñez Lobato, Carlos
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Nano Photonics. KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Kai, Wang
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Schöll, Eva
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Hammar, Mattias
    KTH, Superseded Departments (pre-2005), Microelectronics and Information Technology, IMIT. KTH, Superseded Departments (pre-2005), Electronics. KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Integrated devices and circuits.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    On-demand generation of entangled photon pairs in the telecom C-band for fiber-based quantum networksManuscript (preprint) (Other academic)
    Abstract [en]

    On–demand sources of entangled photons for the transmission of quantum information in the telecom C–band are required to realize fiber–based quantum networks. So far, non–deterministic sources of quantum states of light were used for long distance entanglement distribution in this lowest loss wavelength range. However, they are fundamentally limited in either efficiency or security due to their Poissonian emission statistics. Here, we show on–demand generation of entangled photon pairs in the telecom C-band by an InAs/GaAs semiconductor quantum dot. Using a robust phonon–assisted excitation scheme we measurea concurrence of 91.4% and a fidelity of 95.2% to Φ+ . On–demand generation of polarization entangled photons will enable secure quantum communication in fiber–based networks.Furthermore, applying this excitation scheme to several remote quantum dots tuned into resonance will enable first on–demand entanglement distribution over large distances for scalable real–life quantum applications.

  • 46.
    Zichi, Julien
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Yang, Lily
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Lettner, Thomas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Errando-Herranz, Carlos
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    Jöns, Klaus D.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Baghban, Mohammad Amin
    Gallo, Katia
    Steinhauer, Stephan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Heterogeneous integration of NbTiN by universal room temperature depositionManuscript (preprint) (Other academic)
    Abstract [en]

    Being the Nb-based compound with the highest known critical temperature, NbTiN is of particular interest for many applications. It is used in Josephson junctions for single flux quantum logic gates, as a superconducting electrode to contact semiconductor devices, and one important use is in superconducting nanowire single photon detectors. These detectors are the ideal candidate for on-chip integration in photonic circuits, offering near-unity detection efficiency, low noise and excellent time resolution, therefore it is desirable to implement them on a wide variety of platforms. However, it remains a challenge to deposit the superconducting material with a process suitable for heterogeneous integration, as the most widespread material, NbN, is associated with a deposition at a high temperature. Taking advantage of the possibility to deposit superconducting NbTiN with various stoichiometries by co-sputter deposition at room temperature, we demonstrate growth on six different substrates – silicon dioxide, silicon nitride, gallium arsenide, lithium niobate, [Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] or PMN-PT, and aluminum nitride – in the same deposition run, and show that all the films exhibit superconducting properties with similar critical temperatures. We fabricated waveguide-compatible superconducting nanowire single photon detectors on five substrates, report short dead times for all devices with a narrow spread of performances, and discuss their different photon detection saturation behavior. Our method simplifies the fabrication of superconducting devices on a wide range of materials.

1 - 46 of 46
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