Shortly after their inception, superconducting nanowire single-photon detectors(SNSPDs) became the leading quantum light detection technology. With the capability of detecting single-photons with near-unity efficiency...Shortly after their inception, superconducting nanowire single-photon detectors(SNSPDs) became the leading quantum light detection technology. With the capability of detecting single-photons with near-unity efficiency,high time resolution, low dark count rate, and fast recovery time, SNSPDs outperform conventional single-photon detection techniques. However, detecting lower energy single photons(<0.8 eV) with high efficiency and low timing jitter has remained a challenge. To achieve unity internal efficiency at mid-infrared wavelengths, previous works used amorphous superconducting materials with low energy gaps at the expense of reduced time resolution(close to a nanosecond), and by operating them in complex milli Kelvin(mK) dilution refrigerators. In this work,we provide an alternative approach with SNSPDs fabricated from 5 to 9.5 nm thick NbTiN superconducting films and devices operated in conventional Gifford-McMahon cryocoolers. By optimizing the superconducting film deposition process, film thickness, and nanowire design, our fiber-coupled devices achieved >70% system detection efficiency(SDE) at 2 μm and sub-15 ps timing jitter. Furthermore, detectors from the same batch demonstrated unity internal detection efficiency at 3 μm and 80% internal efficiency at 4 μm, paving the road for an efficient mid-infrared single-photon detection technology with unparalleled time resolution and without mK cooling requirements. We also systematically studied the dark count rates(DCRs) of our detectors coupled to different types of mid-infrared optical fibers and blackbody radiation filters. This offers insight into the trade-off between bandwidth and DCRs for mid-infrared SNSPDs. To conclude, this paper significantly extends the working wavelength range for SNSPDs made from polycrystalline NbTiN to 1.5–4 μm, and we expect quantum optics experiments and applications in the mid-infrared range to benefit from this far-reaching technology.展开更多
Since the discovery of topological insulators,topological phases have generated considerable attention across the physics community.The superlattices in particular offer a rich system with several degrees of freedom t...Since the discovery of topological insulators,topological phases have generated considerable attention across the physics community.The superlattices in particular offer a rich system with several degrees of freedom to explore a variety of topological characteristics and control the localization of states.Albeit their importance,characterizing topological invariants in superlattices consisting of a multi-band structure is challenging beyond the basic case of two-bands as in the Su–Schreifer–Heeger model.Here,we experimentally demonstrate the direct measurement of the topological character of chiral superlattices with broken inversion symmetry.Using a CMOS-compatible nanophotonic chip,we probe the state evolving in the system along the propagation direction using novel nanoscattering structures.We employ a two-waveguide bulk excitation scheme to the superlattice,enabling the identification of topological zero-energy modes through measuring the beam displacement.Our measurements reveal quantized beam displacement corresponding to 0.088 and-0.245,in the cases of trivial and nontrivial photonic superlattices,respectively,showing good agreement with the theoretical values of 0 and-0.25.Our results provide direct identification of the quantized topological numbers in superlattices using a single-shot approach,paving the way for direct measurements of topological invariants in complex photonic structures using tailored excitations with Wannier functions.展开更多
基金Vetenskapsradet(2016-06122,Research Environment Grant2013-7152,International Recruitment of Leading Researchers)+4 种基金Knut och Alice Wallenbergs Stiftelse(Quantum Sensors)EU(899580,FET-Open project)European Commission(H2020-MSCA-ITN-642656,Marie-Sklodowska Curie action Phonsi777222,ATTRACT project)China Scholarship Council(201603170247).
文摘Shortly after their inception, superconducting nanowire single-photon detectors(SNSPDs) became the leading quantum light detection technology. With the capability of detecting single-photons with near-unity efficiency,high time resolution, low dark count rate, and fast recovery time, SNSPDs outperform conventional single-photon detection techniques. However, detecting lower energy single photons(<0.8 eV) with high efficiency and low timing jitter has remained a challenge. To achieve unity internal efficiency at mid-infrared wavelengths, previous works used amorphous superconducting materials with low energy gaps at the expense of reduced time resolution(close to a nanosecond), and by operating them in complex milli Kelvin(mK) dilution refrigerators. In this work,we provide an alternative approach with SNSPDs fabricated from 5 to 9.5 nm thick NbTiN superconducting films and devices operated in conventional Gifford-McMahon cryocoolers. By optimizing the superconducting film deposition process, film thickness, and nanowire design, our fiber-coupled devices achieved >70% system detection efficiency(SDE) at 2 μm and sub-15 ps timing jitter. Furthermore, detectors from the same batch demonstrated unity internal detection efficiency at 3 μm and 80% internal efficiency at 4 μm, paving the road for an efficient mid-infrared single-photon detection technology with unparalleled time resolution and without mK cooling requirements. We also systematically studied the dark count rates(DCRs) of our detectors coupled to different types of mid-infrared optical fibers and blackbody radiation filters. This offers insight into the trade-off between bandwidth and DCRs for mid-infrared SNSPDs. To conclude, this paper significantly extends the working wavelength range for SNSPDs made from polycrystalline NbTiN to 1.5–4 μm, and we expect quantum optics experiments and applications in the mid-infrared range to benefit from this far-reaching technology.
基金Vetenskapsrodet(2016-03905,2019-04821)VINNOVA+1 种基金Wallenberg Center for Quantum TechnologyChalmers University of Technology。
文摘Since the discovery of topological insulators,topological phases have generated considerable attention across the physics community.The superlattices in particular offer a rich system with several degrees of freedom to explore a variety of topological characteristics and control the localization of states.Albeit their importance,characterizing topological invariants in superlattices consisting of a multi-band structure is challenging beyond the basic case of two-bands as in the Su–Schreifer–Heeger model.Here,we experimentally demonstrate the direct measurement of the topological character of chiral superlattices with broken inversion symmetry.Using a CMOS-compatible nanophotonic chip,we probe the state evolving in the system along the propagation direction using novel nanoscattering structures.We employ a two-waveguide bulk excitation scheme to the superlattice,enabling the identification of topological zero-energy modes through measuring the beam displacement.Our measurements reveal quantized beam displacement corresponding to 0.088 and-0.245,in the cases of trivial and nontrivial photonic superlattices,respectively,showing good agreement with the theoretical values of 0 and-0.25.Our results provide direct identification of the quantized topological numbers in superlattices using a single-shot approach,paving the way for direct measurements of topological invariants in complex photonic structures using tailored excitations with Wannier functions.
