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  • 1. Assali, S.
    et al.
    Laehnemann, J.
    Vu, T. T. T.
    Jöns, Klaus
    KTH, School of Engineering Sciences (SCI), Applied Physics. 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.
    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.

  • 3.
    Elshaari, Ali W.
    et al.
    Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    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
    Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    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, Quantum and Biophotonics. Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    Gyger, Samuel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    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, Quantum and Biophotonics. Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    Zwiller, Val
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics. Royal Inst Technol KTH, Dept Appl Phys, Quantum Nano Photon Grp, S-10691 Stockholm, Sweden..
    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.

  • 4.
    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.

  • 5.
    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.

  • 6.
    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, ISSN 2041-1723, 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.

  • 7.
    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, ISSN 1097-5764, 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.

  • 8.
    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.

  • 9.
    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.

  • 10.
    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, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, no 1, article id 7751Article in journal (Refereed)
  • 11.
    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, ISSN 2045-2322, 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.

  • 12.
    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.

  • 13.
    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.

  • 14. 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.

  • 15.
    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.

  • 16. 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.

  • 17.
    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.

  • 18.
    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 D.
    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.

  • 19.
    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.

  • 20. 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%.

  • 21.
    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), Electronics.
    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), Electronics.
    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. 

  • 22.
    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), 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 - 22 of 22
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