352 research outputs found
Quantum cryptography protocols robust against photon number splitting attacks for weak laser pulses implementations
We introduce a new class of quantum quantum key distribution protocols,
tailored to be robust against photon number splitting (PNS) attacks. We study
one of these protocols, which differs from the BB84 only in the classical
sifting procedure. This protocol is provably better than BB84 against PNS
attacks at zero error.Comment: 4 pages, 2 figure
Highly nonclassical photon statistics in parametric down conversion
We use photon counters to obtain the joint photon counting statistics from
twin-beam non-degenerate parametric down conversion, and we demonstrate
directly, and with no auxiliary assumptions, that these twin beams are
nonclassical
Tight focusing of plane waves from micro-fabricated spherical mirrors
We derive a formula for the light field of a monochromatic plane wave that is
truncated and reflected by a spherical mirror. Our formula is valid even for
deep mirrors, where the aperture radius approaches the radius of curvature. We
apply this result to micro-fabricated mirrors whose size scales are in the
range of tens to hundreds of wavelengths, and show that sub-wavelength spot
sizes can be achieved. This opens up the possibility of scalable arrays of
tightly focused optical dipole traps without the need for high-performance
optical systems.Comment: 8 pages, 5 color figures, 1 .sty file; changes made in response to
referee comments; published in Optics Expres
Experimental demonstration of phase measurement precision beating standard quantum limit by projection measurement
We propose and demonstrate experimentally a projection scheme to measure the
quantum phase with a precision beating the standard quantum limit. The initial
input state is a twin Fock state proposed by Holland and Burnett [Phys.
Rev. Lett. {\bf 71}, 1355 (1993)] but the phase information is extracted by a
quantum state projection measurement. The phase precision is about for
large photon number , which approaches the Heisenberg limit of 1/N.
Experimentally, we employ a four-photon state from type-II parametric
down-conversion and achieve a phase uncertainty of beating the
standard quantum limit of for four photons.Comment: 5 figure
Cell-to-cell variability of alternative RNA splicing
The role of mRNA processing in gene expression variability is poorly characterized. This study investigates the extent of cell-to-cell variability of alternative RNA splicing in mammalian cells using single-molecule imaging of CAPRIN1 and MKNK2 splice isoforms
Crosstalk calibration of multi-pixel photon counters using coherent states
We present a novel method of calibration of crosstalk probability for
multi-pixel photon counters (MPPCs) based on the measurement of the normalized
second-order intensity correlation function of coherent light. The method was
tested for several MPPCs, and was shown to be advantageous over the traditional
calibration method based on the measurements of the dark noise statistics. The
method can be applied without the need of modification for different kinds of
spatially resolved single photon detectors.Comment: 8 pages, 3 figures, 2 table
Temporal trends and lesion sets for persistent atrial fibrillation ablation: a meta-analysis with trial sequential analysis and meta-regression
BACKGROUND: Ablation for persistent atrial fibrillation (PsAF) has been performed for over 20 years, although success rates have remained modest. Several adjunctive lesion sets have been studied but none have become standard of practice. We sought to describe how the efficacy of ablation for PsAF has evolved in this time period with a focus on the effect of adjunctive ablation strategies. METHODS: Databases were searched for prospective studies of PsAF ablation. We performed meta-regression and trial sequential analysis. RESULTS: A total of 99 studies (15 424 patients) were included. Ablation for PsAF achieved the primary outcome (freedom of atrial fibrillation/atrial tachycardia rate at 12 months follow-up) in 48.2% (5% CI, 44.0-52.3). Meta-regression showed freedom from atrial arrhythmia at 12 months has improved over time, while procedure time and fluoroscopy time have significantly reduced. Through the use of cumulative meta-analyses and trial sequential analysis, we show that some ablation strategies may initially seem promising, but after several randomized controlled trials may be found to be ineffective. Trial sequential analysis showed that complex fractionated atrial electrogram ablation is ineffective and further study of this treatment would be futile, while posterior wall isolation currently does not have sufficient evidence for routine use in PsAF ablation. CONCLUSIONS: Overall success rates from PsAF ablation and procedure/fluoroscopy times have improved over time. However, no adjunctive lesion set, in addition to pulmonary vein isolation, has been conclusively demonstrated to be beneficial. Through the use of trial sequential analysis, we highlight the importance of adequately powered randomized controlled trials, to avoid reaching premature conclusions, before widespread adoption of novel therapies
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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