44 research outputs found
Superconducting Single-photon Detectors Made of Ultra-thin VN Films
We optimized technology of thin VN films deposition in order to study VN-based superconducting single-photon detectors. Investigation of the main VN film parameters showed that this material has lower resistivity compared to commonly used NbN. Fabricated from obtained films devices showed 100% intrinsic detection efficiency at 900 nm, at the temperature of 1.7 K starting with the bias current of 0.7·
Gated Mode Superconducting Nanowire Single Photon Detectors
Single Photon Detectors (SPD) are fundamental to quantum optics and quantum
information. Superconducting Nanowire SPDs (SNSPD) [1] provide high performance
in terms of quantum efficiency (QE), dark count rate (DCR) and timing jitter
[2], but have limited maximum count rate (MCR) when operated as a free-running
mode (FM) detector [3, 4]. However, high count rates are needed for many
applications like quantum computing [5] and communication [6], and laser
ranging [7]. Here we report the first operation of SNSPDs in a gated mode (GM)
that exploits a single photon triggered latching phenomenon to detect photons.
We demonstrate operation of a large active area single element GM-SNSPD at
625MHz, one order of magnitude faster than its FM counterpart. Contrary to
FM-SNSPDs, the MCR in GM can be pushed to GHz range without a compromise on the
active area or QE, while reducing the DCR
Superconducting parallel nanowire detector with photon number resolving functionality
We present a new photon number resolving detector (PNR), the Parallel
Nanowire Detector (PND), which uses spatial multiplexing on a subwavelength
scale to provide a single electrical output proportional to the photon number.
The basic structure of the PND is the parallel connection of several NbN
superconducting nanowires (100 nm-wide, few nm-thick), folded in a meander
pattern. Electrical and optical equivalents of the device were developed in
order to gain insight on its working principle. PNDs were fabricated on 3-4 nm
thick NbN films grown on sapphire (substrate temperature TS=900C) or MgO
(TS=400C) substrates by reactive magnetron sputtering in an Ar/N2 gas mixture.
The device performance was characterized in terms of speed and sensitivity. The
photoresponse shows a full width at half maximum (FWHM) as low as 660ps. PNDs
showed counting performance at 80 MHz repetition rate. Building the histograms
of the photoresponse peak, no multiplication noise buildup is observable and a
one photon quantum efficiency can be estimated to be QE=3% (at 700 nm
wavelength and 4.2 K temperature). The PND significantly outperforms existing
PNR detectors in terms of simplicity, sensitivity, speed, and multiplication
noise
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