We experimentally demonstrate a supercurrent-assisted, hotspot-formation mechanism for ultrafast detection and counting of visible and infrared photons. A photon-induced hotspot leads to a temporary formation of a resistive barrier across the superconducting sensor strip and results in an easily measurable voltage pulse. Subsequent hotspot healing in ∼30 ps time frame, restores the superconductivity (zero-voltage state), and the detector is ready to register another photon. Our device consists of an ultrathin, very narrow NbN strip, maintained at 4.2 K and current-biased close to the critical current. It exhibits an experimentally measured quantum efficiency of ∼20% for 0.81 μm wavelength photons and negligible dark counts.

Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Zinoni, C., Alloing, B., Li, L., Marsili, F., Fiore, A., Lunghi, L., ... Gol'tsman, G. N. (2007). Single-photon experiments at telecommunication wavelengths using nanowire superconducting detectors. Applied Physics Letters, 91(3), 031106-1/3. [031106]. DOI: 10.1063/1.2752108 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The authors report fiber-coupled superconducting single-photon detectors with specifications that exceed those of avalanche photodiodes, operating at telecommunication wavelength, in sensitivity, temporal resolution, and repetition frequency. The improved performance is demonstrated by measuring the intensity correlation function g ͑2͒ ͑͒ of single-photon states at 1300 nm produced by single semiconductor quantum dots.

Time resolution is one of the main characteristics of the single photon detectors besides quantum efficiency and dark count rate. We demonstrate here an ultrafast time-correlated single photon counting (TCSPC) setup consisting of a newly developed single photon counting board SPC-150NX and a superconducting NbN single photon detector with a sensitive area of 7 × 7 μm. The combination delivers a record instrument response function with a full width at half maximum of 17.8 ps and system quantum efficiency ∼15% at wavelength of 1560 nm. A calculation of the root mean square value of the timing jitter for channels with counts more than 1% of the peak value yielded about 7.6 ps. The setup has also good timing stability of the detector-TCSPC board.

No abstract

PACS 74.78.Fk, 85.25.Oj We present our progress on the research and development of NbN superconducting single-photon detectors (SSPD's) for ultrafast counting of near-infrared photons for secure quantum communications. Our SSPD's operate in the quantum detection mode based on the photon-induced hotspot formation and subsequent development of a transient resistive barrier across an ultrathin and submicron-width superconducting stripe. The devices are fabricated from 4-nm-thick NbN films and kept in the 4.2-to 2-K temperature range. The detector experimental quantum efficiency in the photon-counting mode reaches above 40% for the visible light and up to 30% in the 1.3-to 1.55-µm wavelength range with dark counts below 0.01 per second. The experimental real-time counting rate is above 2 GHz and is limited by our readout electronics. The SSPD's timing jitter is below 18 ps, and the best-measured value of the noise-equivalent power (NEP) is 5 × 10 -21 W/Hz 1/2 at 1.3 µm. In terms of quantum efficiency, timing jitter, and maximum counting rate, our NbN SSPD's significantly outperform semiconductor avalanche photodiodes and photomultipliers in the 1.3-to 1.55-µm range.

Published by the AIP Publishing Articles you may be interested inHigh efficiency and rapid response superconducting NbN nanowire single photon detector based on asymmetric split ring metamaterial Appl. Phys. Lett.

No abstract

Numerous studies have revealed changes in gastrointestinal secretion, motility, evacuation, and absorption in humans and animals after actual space missions and under hypokinesia of various duration as well. It is found that short-term space missions produce transient changes in the activity of digestive enzymes, instability of bifido- and lactoflora peculiar to stress reaction, and an enhanced evacuation of the stomach. Extended space missions result in more pronounced but transient changes which characterize mainly two states: development of a hypersecretory syndrome of the stomach and decrease in the functional capacity of the pancreas. As a rule, the changes of membranous enzymes are of compensatory-and-adaptive character. Concurrent with this, there occur disbiotic changes of various degree in the intestinal microflora.