9 research outputs found
Design of broadband high-efficiency superconducting-nanowire single photon detectors
In this paper several designs to maximize the absorption efficiency of
superconducting-nanowire single-photon detectors are investigated. Using a
simple optical cavity consisting of a gold mirror and a SiO2 layer, the
absorption efficiency can be boosted to over 97%: this result is confirmed
experimentally by the realization of an NbTiN-based detector having an overall
system detection efficiency of 85% at 1.31 micrometers. Calculations show that
by sandwiching the nanowire between two dielectric Bragg reflectors, unity
absorption (> 99.9%) could be reached at the peak wavelength for optimized
structures. To achieve broadband high efficiency, a different approach is
considered: a waveguide-coupled detector. The calculations performed in this
work show that, by correctly dimensioning the waveguide and the nanowire,
polarization-insensitive detectors absorbing more than 95% of the injected
photons over a wavelength range of several hundred nm can be designed. We
propose a detector design making use of GaN/AlN waveguides, since these
materials allow lattice-matched epitaxial deposition of Nb(Ti)N films and are
transparent on a very wide wavelength range
In-field entanglement distribution over a 96 km-long submarine optical fibre
Techniques for the distribution of quantum-secured cryptographic keys have
reached a level of maturity allowing them to be implemented in all kinds of
environments, away from any form of laboratory infrastructure. Here, we detail
the distribution of entanglement between Malta and Sicily over a 96 km-long
submarine telecommunications optical fibre cable. We used this standard
telecommunications fibre as a quantum channel to distribute
polarisation-entangled photons and were able to observe around 257 photon pairs
per second, with a polarisation visibility above 90%. Our experiment
demonstrates the feasibility of using deployed submarine telecommunications
optical fibres as long-distance quantum channels for polarisation-entangled
photons. This opens up a plethora of possibilities for future experiments and
technological applications using existing infrastructure.Comment: 6 pages, 4 figure
A miniaturized 4 K platform for superconducting infrared photon counting detectors
We report on a miniaturized platform for superconducting infrared photon counting detectors. We have implemented a fibre-coupled superconducting nanowire single photon detector in a Stirling/Joule–Thomson platform with a base temperature of 4.2 K. We have verified a cooling power of 4 mW at 4.7 K. We report 20% system detection efficiency at 1310 nm wavelength at a dark count rate of 1 kHz. We have carried out compelling application demonstrations in single photon depth metrology and singlet oxygen luminescence detection
High absorption efficiency and polarization-insensitivity in superconducting-nanowire single-photon detectors
International audienceThe performance of superconducting-nanowire single-photon detectors depends on the efficiency of light absorption in the ultrathin (3-8 nm) superconducting nanowire. In this work, we will discuss two approaches to boost light absorption: coupling the nanowire to the evanescent field propagating in a waveguide and enclosing the nanowire in an optical cavity. The latter method is the most widely used, but it is intrinsically very sensitive to the polarization of light. To overcome this issue, we propose some innovative cavity designs which make use of high-index (n >2) dielectrics. With this technique, highly-efficient polarization-insensitive devices can be easily implemented
Single-photon detectors combining high efficiency, high detection rates, and ultra-high timing resolution
Single-photon detection with high efficiency, high time resolution, low dark counts, and
high photon detection rates is crucial for a wide range of optical measurements. Although
efficient detectors have been reported before, combining all performance parameters in a
single device remains a challenge. Here, we show a broadband NbTiN superconducting
nanowire detector with an efficiency exceeding 92%, over 150 MHz photon detection rate,
and a dark count rate below 130 Hz operated in a Gifford-McMahon cryostat. Furthermore,
with careful optimization of the detector design and readout electronics, we reach an
ultra-low system timing jitter of 14.80 ps (13.95 ps decoupled) while maintaining high
detection efficiencies (>75%)