240 research outputs found
Passive scheme with a photon-number-resolving detector for monitoring the untrusted source in a plug-and-play quantum-key-distribution system
A passive scheme with a beam splitter and a photon-number-resolving (PNR)
detector is proposed to verify the photon statistics of an untrusted source in
a plug-and-play quantum-key-distribution system by applying a three-intensity
decoy-state protocol. The practical issues due to statistical fluctuation and
detection noise are analyzed. The simulation results show that the scheme can
work efficiently when the total number of optical pulses sent from Alice to Bob
is above 10^8, and the dark count rate of the PNR detector is below 0.5
counts/pulse, which is realizable with current techniques. Furthermore, we
propose a practical realization of the PNR detector with a variable optical
attenuator combined with a threshold detector.Comment: 8 pages, 6 figure
Source monitoring for continuous-variable quantum key distribution
The noise in optical source needs to be characterized for the security of
continuous-variable quantum key distribution (CVQKD). Two feasible schemes,
based on either active optical switch or passive beamsplitter are proposed to
monitor the variance of source noise, through which, Eve's knowledge can be
properly estimated. We derive the security bounds for both schemes against
collective attacks in the asymptotic case, and find that the passive scheme
performs better.Comment: The first version. 9 pages and 4 figure
Accurate Eye Tracking from Dense 3D Surface Reconstructions using Single-Shot Deflectometry
Eye-tracking plays a crucial role in the development of virtual reality
devices, neuroscience research, and psychology. Despite its significance in
numerous applications, achieving an accurate, robust, and fast eye-tracking
solution remains a considerable challenge for current state-of-the-art methods.
While existing reflection-based techniques (e.g., "glint tracking") are
considered the most accurate, their performance is limited by their reliance on
sparse 3D surface data acquired solely from the cornea surface. In this paper,
we rethink the way how specular reflections can be used for eye tracking: We
propose a novel method for accurate and fast evaluation of the gaze direction
that exploits teachings from single-shot phase-measuring-deflectometry (PMD).
In contrast to state-of-the-art reflection-based methods, our method acquires
dense 3D surface information of both cornea and sclera within only one single
camera frame (single-shot). Improvements in acquired reflection surface
points("glints") of factors are easily achievable. We show the
feasibility of our approach with experimentally evaluated gaze errors of only
demonstrating a significant improvement over the current
state-of-the-art
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