116 research outputs found
Bright Integrated Photon-Pair Source for Practical Passive Decoy-State Quantum Key Distribution
We report on a bright, nondegenerate type-I parametric down-conversion
source, which is well suited for passive decoy-state quantum key distribution.
We show the photon-number-resolved analysis over a broad range of pump powers
and we prove heralded higher-order -photon states up to . The inferred
photon click statistics exhibit excellent agreements to the theoretical
predictions. From our measurement results we conclude that our source meets the
requirements to avert photon-number-splitting attacks.Comment: 5 pages, 4 figure
Fundamental constraints on particle tracking with optical tweezers
A general quantum limit to the sensitivity of particle position measurements
is derived following the simple principle of the Heisenberg microscope. The
value of this limit is calculated for particles in the Rayleigh and Mie
scattering regimes, and with parameters which are relevant to optical tweezers
experiments. The minimum power required to observe the zero-point motion of a
levitating bead is also calculated, with the optimal particle diameter always
smaller than the wavelength. We show that recent optical tweezers experiments
are within two orders of magnitude of quantum limited sensitivity, suggesting
that quantum optical resources may soon play an important role in high
sensitivity tracking applications
How well can superconducting nanowire single-photon detectors resolve photon number?
We apply principal component analysis (PCA) to a set of electrical output
signals from a commercially available superconducting nanowire single-photon
detector (SNSPD) to investigate their photon-number-resolving capability. We
find that the rising edge as well as the amplitude of the electrical signal
have the most dependence on photon number. Accurately measuring the rising edge
while simultaneously measuring the voltage of the pulse amplitude maximizes the
photon-number resolution of SNSPDs. Using an optimal basis of principle
components, we show unambiguous discrimination between one- and two-photon
events, as well as partial resolution up to five photons. This expands the
use-case of SNSPDs to photon-counting experiments, without the need of detector
multiplexing architectures.Comment: 7 pages, 5 figure
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