20 research outputs found
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
Quantum Communication
Quantum communication, and indeed quantum information in general, has changed
the way we think about quantum physics. In 1984 and 1991, the first protocol
for quantum cryptography and the first application of quantum non-locality,
respectively, attracted a diverse field of researchers in theoretical and
experimental physics, mathematics and computer science. Since then we have seen
a fundamental shift in how we understand information when it is encoded in
quantum systems. We review the current state of research and future directions
in this new field of science with special emphasis on quantum key distribution
and quantum networks.Comment: Submitted version, 8 pg (2 cols) 5 fig
Testing foundations of quantum mechanics with photons
The foundational ideas of quantum mechanics continue to give rise to
counterintuitive theories and physical effects that are in conflict with a
classical description of Nature. Experiments with light at the single photon
level have historically been at the forefront of tests of fundamental quantum
theory and new developments in photonics engineering continue to enable new
experiments. Here we review recent photonic experiments to test two
foundational themes in quantum mechanics: wave-particle duality, central to
recent complementarity and delayed-choice experiments; and Bell nonlocality
where recent theoretical and technological advances have allowed all
controversial loopholes to be separately addressed in different photonics
experiments.Comment: 10 pages, 5 figures, published as a Nature Physics Insight review
articl
A Single-Photon Imager Based on Microwave Plasmonic Superconducting Nanowire
Detecting spatial and temporal information of individual photons by using
single-photon-detector (SPD) arrays is critical to applications in
spectroscopy, communication, biological imaging, astronomical observation, and
quantum-information processing. Among the current SPDs1,detectors based on
superconducting nanowires have outstanding performance2, but are limited in
their ability to be integrated into large scale arrays due to the engineering
difficulty of high-bandwidth cryogenic electronic readout3-8. Here, we address
this problem by demonstrating a scalable single-photon imager using a single
continuous photon-sensitive superconducting nanowire microwave-plasmon
transmission line. By appropriately designing the nanowire's local
electromagnetic environment so that the nanowire guides microwave plasmons, the
propagating voltages signals generated by a photon-detection event were slowed
down to ~ 2% of the speed of light. As a result, the time difference between
arrivals of the signals at the two ends of the nanowire naturally encoded the
position and time of absorption of the photon. Thus, with only two readout
lines, we demonstrated that a 19.7-mm-long nanowire meandered across an area of
286 {\mu}m * 193 {\mu}m was capable of resolving ~590 effective pixels while
simultaneously recording the arrival times of photons with a temporal
resolution of 50 ps. The nanowire imager presents a scalable approach to
realizing high-resolution photon imaging in time and space
Improvement of infrared single-photon detectors absorptance by integrated plasmonic structures
Plasmonic structures open novel avenues in photodetector development. Optimized illumination configurations are reported to improve p-polarized light absorptance in superconducting-nanowire single-photon detectors (SNSPDs) comprising short- and long-periodic niobium-nitride (NbN) stripe-patterns. In OC-SNSPDs consisting of ~quarter-wavelength dielectric layer closed by a gold reflector the highest absorptance is attainable at perpendicular incidence onto NbN patterns in P-orientation due to E-field concentration at the bottom of nano-cavities. In NCAI-SNSPDs integrated with nano-cavity-arrays consisting of vertical and horizontal gold segments off-axis illumination in S-orientation results in polar-angle-independent perfect absorptance via collective resonances in short-periodic design, while in long-periodic NCAI-SNSPDs grating-coupled surface waves promote EM-field transportation to the NbN stripes and result in local absorptance maxima. In NCDAI-SNSPDs integrated with nano-cavity-deflector-array consisting of longer vertical gold segments large absorptance maxima appear in 3p-periodic designs due to E-field enhancement via grating-coupled surface waves synchronized with the NbN stripes in S-orientation, which enable to compensate fill-factor-related retrogression.United States. Dept. of Energy (Frontier Research Centers
Single-photon experiments at telecommunication wavelengths using nanowire superconducting detectors
The authors report fiber-coupled superconducting single-photon detectors with specifications that exceed those of avalanche photodiodes, operating at telecommunication wavelength, in sensitivity, temporal resoln., and repetition frequency. The improved performance is demonstrated by measuring the intensity correlation function g(2)(t) of single-photon states at 1300 nm produced by single semiconductor quantum dots. [on SciFinder (R)