Professional Education

  • Master of Science, ETH Zurich (2017)
  • Bachelor of Science, ETH Zurich (2015)
  • Doctor of Philosophy, Kungliga Tekniska Hogskolan (2022)
  • Doctor of Philosophy, KTH Royal Institute of Technology, Stockholm, Sweden, Physics / Integrated photonics for quantum optics. (2022)

Stanford Advisors

Research Interests

  • Alternative Schooling
  • Data Sciences
  • Research Methods

All Publications

  • Wavelength-Sensitive Superconducting Single-Photon Detectors on Thin Film Lithium Niobate Waveguides. Nano letters Prencipe, A., Gyger, S., Baghban, M. A., Zichi, J., Zeuner, K. D., Lettner, T., Schweickert, L., Steinhauer, S., Elshaari, A. W., Gallo, K., Zwiller, V. 2023


    Lithium niobate, because of its nonlinear and electro-optical properties, is one of the materials of choice for photonic applications. The development of nanostructuring capabilities of thin film lithium niobate (TFLN) permits fabrication of small footprint, low-loss optical circuits. With the recent implementation of on-chip single-photon detectors, this architecture is among the most promising for realizing on-chip quantum optics experiments. In this Letter, we report on the implementation of superconducting nanowire single-photon detectors (SNSPDs) based on NbTiN on 300 nm thick TFLN ridge nano-waveguides. We demonstrate a waveguide-integrated wavelength meter based on the photon energy dependence of the superconducting detectors. The device operates at the telecom C- and L-bands and has a footprint smaller than 300 × 180 μm2 and critical currents between ∼12 and ∼14 μA, which ensures operation with minimum heat dissipation. Our results hold promise for future densely packed on-chip wavelength-multiplexed quantum communication systems.

    View details for DOI 10.1021/acs.nanolett.3c02324

    View details for PubMedID 37871304

  • Metropolitan single-photon distribution at 1550 nm for random number generation APPLIED PHYSICS LETTERS Gyger, S., Zeuner, K. D., Lettner, T., Bensoussan, S., Carlnas, M., Ekemar, L., Schweickert, L., Hedlund, C., Hammar, M., Nilsson, T., Almlof, J., Steinhauer, S., Llosera, G., Zwiller, V. 2022; 121 (19)

    View details for DOI 10.1063/5.0112939

    View details for Web of Science ID 000884565500003

  • Strain-Controlled Quantum Dot Fine Structure for Entangled Photon Generation at 1550 nm. Nano letters Lettner, T., Gyger, S., Zeuner, K. D., Schweickert, L., Steinhauer, S., Reuterskiöld Hedlund, C., Stroj, S., Rastelli, A., Hammar, M., Trotta, R., Jöns, K. D., Zwiller, V. 2021; 21 (24): 10501-10506


    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.

    View details for DOI 10.1021/acs.nanolett.1c04024

    View details for PubMedID 34894699

    View details for PubMedCentralID PMC8704189

  • Efficient and versatile toolbox for analysis of time-tagged measurements JOURNAL OF INSTRUMENTATION Lin, Z., Schweickert, L., Gyger, S., Jons, K. D., Zwiller, V. 2021; 16 (8)
  • Reconfigurable photonics with on-chip single-photon detectors. Nature communications Gyger, S., Zichi, J., Schweickert, L., Elshaari, A. W., Steinhauer, S., Covre da Silva, S. F., Rastelli, A., Zwiller, V., Jöns, K. D., Errando-Herranz, C. 2021; 12 (1): 1408


    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.

    View details for DOI 10.1038/s41467-021-21624-3

    View details for PubMedID 33658495

    View details for PubMedCentralID PMC7930283

  • Single-mode squeezed-light generation and tomography with an integrated optical parametric oscillator. Science advances Park, T., Stokowski, H., Ansari, V., Gyger, S., Multani, K. K., Celik, O. T., Hwang, A. Y., Dean, D. J., Mayor, F., McKenna, T. P., Fejer, M. M., Safavi-Naeini, A. 2024; 10 (11): eadl1814


    Quantum optical technologies promise advances in sensing, computing, and communication. A key resource is squeezed light, where quantum noise is redistributed between optical quadratures. We introduce a monolithic, chip-scale platform that exploits the χ(2) nonlinearity of a thin-film lithium niobate (TFLN) resonator device to efficiently generate squeezed states of light. Our system integrates all essential components-except for the laser and two detectors-on a single chip with an area of one square centimeter, reducing the size, operational complexity, and power consumption associated with conventional setups. Using the balanced homodyne measurement subsystem that we implemented on the same chip, we measure a squeezing of 0.55 decibels and an anti-squeezing of 1.55 decibels. We use 20 milliwatts of input power to generate the parametric oscillator pump field by using second harmonic generation on the same chip. Our work represents a step toward compact and efficient quantum optical systems posed to leverage the rapid advances in integrated nonlinear and quantum photonics.

    View details for DOI 10.1126/sciadv.adl1814

    View details for PubMedID 38478618

  • Superconducting single-photon detectors fabricated via a focused electron beam-induced deposition process AIP ADVANCES Steinhauer, S., Iovan, A., Gyger, S., Zwiller, V. 2023; 13 (4)

    View details for DOI 10.1063/5.0080674

    View details for Web of Science ID 000973660000002

  • Fractal superconducting nanowire single-photon detectors working in dual bands and their applications in free-space and underwater hybrid LIDAR. Optics letters Zou, K., Hao, Z., Feng, Y., Meng, Y., Hu, N., Steinhauer, S., Gyger, S., Zwiller, V., Hu, X. 2023; 48 (2): 415-418


    We demonstrate a fiber-coupled fractal superconducting nanowire single-photon detector (SNSPD) system with minimum polarization dependence of detection efficiency. Its system detection efficiency (SDE) was maximized at the wavelength of 1540 nm, which was measured to be 91±4%; furthermore, we observed the second local maximum of SDE at the wavelength of 520 nm, which was measured to be 61±2%. This dual-band feature of SDE was due to the enhancement of the optical absorptance by two longitudinal resonance modes of the micro-cavity. By using high SDE with minimum polarization dependence in these two bands, we implemented a hybrid LIDAR for imaging the remote objects in free space and under water.

    View details for DOI 10.1364/OL.481226

    View details for PubMedID 36638471

  • Phonon heat capacity and self-heating normal domains in NbTiN nanostrips SUPERCONDUCTOR SCIENCE & TECHNOLOGY Sidorova, M., Semenov, A. D., Huebers, H., Gyger, S., Steinhauer, S. 2022; 35 (10)
  • Observation of Anderson phase in a topological photonic circuit PHYSICAL REVIEW RESEARCH Gao, J., Xu, Z., Smirnova, D. A., Leykam, D., Gyger, S., Zhou, W., Steinhauer, S., Zwiller, V., Elshaari, A. W. 2022; 4 (3)
  • Current Crowding in Nanoscale Superconductors within the Ginzburg-Landau Model PHYSICAL REVIEW APPLIED Jonsson, M., Vedin, R., Gyger, S., Sutton, J. A., Steinhauer, S., Zwiller, V., Wallin, M., Lidmar, J. 2022; 17 (6)
  • Fractal Superconducting Nanowires Detect Infrared Single Photonswith 84% System Detection Efficiency, 1.02 Polarization Sensitivity,and 20.8 ps Timing Resolution ACS PHOTONICS Meng, Y., Zou, K., Hu, N., Xu, L., Lan, X., Steinhauer, S., Gyger, S., Zwiller, V., Hu, X. 2022; 9 (5): 1547-1553
  • Full-Stokes polarimetric measurements and imaging using a fractal superconducting nanowire single-photon detector OPTICA Hu, N., Meng, Y., Zou, K., Feng, Y., Hao, Z., Steinhauer, S., Gyger, S., Zwiller, V., Hu, X. 2022; 9 (4): 346-351
  • Giant Rydberg excitons in Cu2O probed by photoluminescence excitation spectroscopy PHYSICAL REVIEW B Versteegh, M. M., Steinhauer, S., Bajo, J., Lettner, T., Soro, A., Romanova, A., Gyger, S., Schweickert, L., Mysyrowicz, A., Zwiller, V. 2021; 104 (24)
  • Magnetoconductance and photoresponse properties of disordered NbTiN films PHYSICAL REVIEW B Sidorova, M., Semenov, A. D., Huebers, H., Gyger, S., Steinhauer, S., Zhang, X., Schilling, A. 2021; 104 (18)
  • Enhancing Si3N4 Waveguide Nonlinearity with Heterogeneous Integration of Few-Layer WS2. ACS photonics Wang, Y., Pelgrin, V., Gyger, S., Uddin, G. M., Bai, X., Lafforgue, C., Vivien, L., Jöns, K. D., Cassan, E., Sun, Z. 2021; 8 (9): 2713-2721


    The heterogeneous integration of low-dimensional materials with photonic waveguides has spurred wide research interest. Here, we report on the experimental investigation and the numerical modeling of enhanced nonlinear pulse broadening in silicon nitride waveguides with the heterogeneous integration of few-layer WS2. After transferring a few-layer WS2 flake of ∼14.8 μm length, the pulse spectral broadening in a dispersion-engineered silicon nitride waveguide has been enhanced by ∼48.8% in bandwidth. Through numerical modeling, an effective nonlinear coefficient higher than 600 m-1 W-1 has been retrieved for the heterogeneous waveguide indicating an enhancement factor of larger than 300 with respect to the pristine waveguide at a wavelength of 800 nm. With further advances in two-dimensional material fabrication and integration techniques, on-chip heterostructures will offer another degree of freedom for waveguide engineering, enabling high-performance nonlinear optical devices, such as frequency combs and quantum light sources.

    View details for DOI 10.1021/acsphotonics.1c00767

    View details for PubMedID 34553003

    View details for PubMedCentralID PMC8447258

  • On-Demand Generation of Entangled Photon Pairs in the Telecom C-Band with InAs Quantum Dots ACS PHOTONICS Zeuner, K. D., Jons, K. D., Schweickert, L., Hedlund, C., Lobato, C., Lettner, T., Wang, K., Gyger, S., Scholl, E., Steinhauer, S., Hammar, M., Zwiller, V. 2021; 8 (8): 2337-2344


    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 Φ+ 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.

    View details for DOI 10.1021/acsphotonics.1c00504

    View details for Web of Science ID 000687190500019

    View details for PubMedID 34476289

    View details for PubMedCentralID PMC8377713

  • Superconducting nanowire single-photon detectors: A perspective on evolution, state-of-the-art, future developments, and applications APPLIED PHYSICS LETTERS Esmaeil Zadeh, I., Chang, J., Los, J. N., Gyger, S., Elshaari, A. W., Steinhauer, S., Dorenbos, S. N., Zwiller, V. 2021; 118 (19)

    View details for DOI 10.1063/5.0045990

    View details for Web of Science ID 000659149400001

  • Deterministic Integration of hBN Emitter in Silicon Nitride Photonic Waveguide ADVANCED QUANTUM TECHNOLOGIES Elshaari, A. W., Skalli, A., Gyger, S., Nurizzo, M., Schweickert, L., Esmaeil Zadeh, I., Svedendahl, M., Steinhauer, S., Zwiller, V. 2021; 4 (6)
  • Resonance Fluorescence from Waveguide-Coupled, Strain-Localized, Two-Dimensional Quantum Emitters. ACS photonics Errando-Herranz, C., Schöll, E., Picard, R., Laini, M., Gyger, S., Elshaari, A. W., Branny, A., Wennberg, U., Barbat, S., Renaud, T., Sartison, M., Brotons-Gisbert, M., Bonato, C., Gerardot, B. D., Zwiller, V., Jöns, K. D. 2021; 8 (4): 1069-1076


    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.

    View details for DOI 10.1021/acsphotonics.0c01653

    View details for PubMedID 34056034

    View details for PubMedCentralID PMC8155555

  • Progress on large-scale superconducting nanowire single-photon detectors APPLIED PHYSICS LETTERS Steinhauer, S., Gyger, S., Zwiller, V. 2021; 118 (10)

    View details for DOI 10.1063/5.0044057

    View details for Web of Science ID 000627444500001

  • Gate-Switchable Arrays of Quantum Light Emitters in Contacted Monolayer MoS2 van der Waals Heterodevices. Nano letters Hötger, A., Klein, J., Barthelmi, K., Sigl, L., Sigger, F., Männer, W., Gyger, S., Florian, M., Lorke, M., Jahnke, F., Taniguchi, T., Watanabe, K., Jöns, K. D., Wurstbauer, U., Kastl, C., Müller, K., Finley, J. J., Holleitner, A. W. 2021; 21 (2): 1040-1046


    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.

    View details for DOI 10.1021/acs.nanolett.0c04222

    View details for PubMedID 33433221

  • Engineering the Luminescence and Generation of Individual Defect Emitters in Atomically Thin MoS2 ACS PHOTONICS Klein, J., Sigl, L., Gyger, S., Barthelmi, K., Florian, M., Rey, S., Taniguchi, T., Watanabe, K., Jahnke, F., Kastl, C., Zwiller, V., Jons, K. D., Mueller, K., Wurstbauer, U., Finley, J. J., Holleitner, A. W. 2021; 8 (2): 669-677
  • Temporal array with superconducting nanowire single-photon detectors for photon-number resolution PHYSICAL REVIEW A Jonsson, M., Swillo, M., Gyger, S., Zwiller, V., Bjork, G. 2020; 102 (5)
  • Dispersion engineering of superconducting waveguides for multi-pixel integration of single-photon detectors APL PHOTONICS Elshaari, A. W., Iovan, A., Gyger, S., Zadeh, I., Zichi, J., Yang, L., Steinhauer, S., Zwiller, V. 2020; 5 (11)

    View details for DOI 10.1063/5.0019734

    View details for Web of Science ID 000587654100001

  • Atomistic defects as single-photon emitters in atomically thin MoS2 APPLIED PHYSICS LETTERS Barthelmi, K., Klein, J., Hoetger, A., Sigl, L., Sigger, F., Mitterreiter, E., Rey, S., Gyger, S., Lorke, M., Florian, M., Jahnke, F., Taniguchi, T., Watanabe, K., Zwiller, Jons, K. D., Wurstbauer, U., Kastl, C., Weber-Bargioni, A., Finley, J. J., Mueller, K., Holleitner, A. W. 2020; 117 (7)

    View details for DOI 10.1063/5.0018557

    View details for Web of Science ID 000563577500001

  • NbTiN thin films for superconducting photon detectors on photonic and two-dimensional materials APPLIED PHYSICS LETTERS Steinhauer, S., Yang, L., Gyger, S., Lettner, T., Errando-Herranz, C., Jons, K. D., Baghban, M., Gallo, K., Zichi, J., Zwiller, V. 2020; 116 (17)

    View details for DOI 10.1063/1.5143986

    View details for Web of Science ID 000530414200001

  • Rydberg excitons in Cu2O microcrystals grown on a silicon platform COMMUNICATIONS MATERIALS Steinhauer, S., Versteegh, M. M., Gyger, S., Elshaari, A. W., Kunert, B., Mysyrowicz, A., Zwiller, V. 2020; 1 (1)
  • GaAs Quantum Dot in a Parabolic Microcavity Tuned to Rb-87 D-1 ACS PHOTONICS Lettner, T., Zeuner, K. D., Scholl, E., Huang, H., Scharmer, S., da Silva, S., Gyger, S., Schweickert, L., Rastelli, A., Jons, K. D., Zwiller, V. 2020; 7 (1): 29-35


    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 D1 line (795 nm).

    View details for DOI 10.1021/acsphotonics.9b01243

    View details for Web of Science ID 000508475800003

    View details for PubMedID 32025532

    View details for PubMedCentralID PMC6994066

  • Reconfigurable frequency coding of triggered single photons in the telecom C-band OPTICS EXPRESS Gyger, S., Zeuner, K. D., Jons, K. D., Elshaari, A. W., Paul, M., Popov, S., Hedlund, C., Hammar, M., Ozolins, O., Zwiller, V. 2019; 27 (10): 14400-14406


    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.

    View details for DOI 10.1364/OE.27.014400

    View details for Web of Science ID 000469220500072

    View details for PubMedID 31163890

  • Strain-Tunable Quantum Integrated Photonics NANO LETTERS Elshaari, A. W., Buyukozer, E., Zadeh, I., Lettner, T., Zhao, P., Scholl, E., Gyger, S., Reimer, M. E., Dalacu, D., Poole, P. J., Jons, K. D., Zwiller, V. 2018; 18 (12): 7969-7976


    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.

    View details for DOI 10.1021/acs.nanolett.8b03937

    View details for Web of Science ID 000453488800074

    View details for PubMedID 30474987

    View details for PubMedCentralID PMC6477803