88 research outputs found
Photon-number resolving detector based on a series array of superconducting nanowires
We present the experimental demonstration of a superconducting photon number
resolving detector. It is based on the series connection of N superconducting
nanowires, each connected in parallel to an integrated resistor. The device
provides a single voltage readout, proportional to the number of photons
absorbed in distinct nanowires. Clearly separated output levels corresponding
to the detection of n=1-4 photons are observed in a 4-element detector
fabricated from an NbN film on GaAs substrate, with a single-photon system
quantum efficiency of 2.6% at the wavelength of 1300nm. The series-nanowire
structure is promising in view of its scalability to large photon numbers and
high efficiencies.Comment: 12 pages, 6 figure
Ultrasensitive N-photon interferometric autocorrelator
We demonstrate a novel method to measure the Nth-order (N=1, 2, 3, 4)
interferometric autocorrelation with high sensitivity and temporal resolution.
It is based on the combination of linear absorption and nonlinear detection in
a superconducting nanodetector, providing much higher efficiency than methods
based on all-optical nonlinearities. Its temporal resolution is only limited by
the quasi-particle energy relaxation time, which is directly measured to be in
the 20 ps range for the NbN films used in this work. We present a general model
of interferometric autocorrelation with these nonlinear detectors and discuss
the comparison with other approaches and possible improvements
Optimal Amplitude Multiplexing of a Series of Superconducting Nanowire Single Photon Detectors
Integrated arrays of Superconducting Nanowire Single Photon Detectors
(SNSPDs) have shown capabilities such as Photon Number Resolution, single
photon imaging and coincidences detection, and can be effectively used also in
other different applications related to quantum optics. The growing complexity
of such applications requires the use of multiplexing schemes for the
simultaneous readout of different detectors. A simple multiplexing scheme can
be realized by arranging a series of SNSPDs elements, shunted by appropriate
resistances. The goal of this work is to investigate and optimize this scheme,
developing a general method able to identify the optimal sets of shunting
resistences for any different application. The methodology obtained is very
general, and can be extended to other detection systems
Superconducting series nanowire detector counting up to twelve photons
We demonstrate a superconducting photon-number-resolving detector capable of
resolving up to twelve photons at telecommunication wavelengths. It is based on
a series array of twelve superconducting NbN nanowire elements, each connected
in parallel with an integrated resistor. The photon-induced voltage signals
from the twelve elements are summed up into a single readout pulse with a
height proportional to the detected photon number. Thirteen distinct output
levels corresponding to the detection of n=0-12 photons are observed
experimentally. A detailed analysis of the excess noise shows the potential of
scaling to an even larger dynamic range.Comment: 13 page
Nidogen-1 is a novel extracellular ligand for the NKp44 activating receptor
The release of soluble ligands of activating Natural Killer (NK) cell receptors may represent a regulatory mechanism of NK cell function both in physiologic and in pathologic conditions. Here, we identified the extracellular matrix protein Nidogen-1 (NID1) as a ligand of NKp44, an important activating receptor expressed by activated NK cells. When released as soluble molecule, NID1 regulates NK cell function by modulating NKp44-induced IFN-\u3b3 production or cytotoxicity. In particular, it also modulates IFN-\u3b3 production induced by Platelet-Derived Growth Factor (PDGF)-DD following NKp44 engagement. We also show that NID1 may be present at the cell surface. In this form or when bound to a solid support (bNID1), NID1 fails to induce NK cell cytotoxicity or cytokine release. However, analysis by mass spectrometry revealed that exposure to bNID1 can induce in human NK cells relevant changes in the proteomic profiles suggesting an effect on different biological processes
Waveguide single-photon detectors for integrated quantum photonic circuits
The generation, manipulation and detection of quantum bits (qubits) encoded
on single photons is at the heart of quantum communication and optical quantum
information processing. The combination of single-photon sources, passive
optical circuits and single-photon detectors enables quantum repeaters and
qubit amplifiers, and also forms the basis of all-optical quantum gates and of
linear-optics quantum computing. However, the monolithic integration of
sources, waveguides and detectors on the same chip, as needed for scaling to
meaningful number of qubits, is very challenging, and previous work on quantum
photonic circuits has used external sources and detectors. Here we propose an
approach to a fully-integrated quantum photonic circuit on a semiconductor
chip, and demonstrate a key component of such circuit, a waveguide
single-photon detector. Our detectors, based on superconducting nanowires on
GaAs ridge waveguides, provide high efficiency (20%) at telecom wavelengths,
high timing accuracy (60 ps), response time in the ns range, and are fully
compatible with the integration of single-photon sources, passive networks and
modulators.Comment: 11 pages, 4 figure
Superconducting nanowire photon number resolving detector at telecom wavelength
The optical-to-electrical conversion, which is the basis of optical
detectors, can be linear or nonlinear. When high sensitivities are needed
single-photon detectors (SPDs) are used, which operate in a strongly nonlinear
mode, their response being independent of the photon number. Nevertheless,
photon-number resolving (PNR) detectors are needed, particularly in quantum
optics, where n-photon states are routinely produced. In quantum communication,
the PNR functionality is key to many protocols for establishing, swapping and
measuring entanglement, and can be used to detect photon-number-splitting
attacks. A linear detector with single-photon sensitivity can also be used for
measuring a temporal waveform at extremely low light levels, e.g. in
long-distance optical communications, fluorescence spectroscopy, optical
time-domain reflectometry. We demonstrate here a PNR detector based on parallel
superconducting nanowires and capable of counting up to 4 photons at
telecommunication wavelengths, with ultralow dark count rate and high counting
frequency
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