95 research outputs found
SURGE: Continuous Detection of Bursty Regions Over a Stream of Spatial Objects
With the proliferation of mobile devices and location-based services,
continuous generation of massive volume of streaming spatial objects (i.e.,
geo-tagged data) opens up new opportunities to address real-world problems by
analyzing them. In this paper, we present a novel continuous bursty region
detection problem that aims to continuously detect a bursty region of a given
size in a specified geographical area from a stream of spatial objects.
Specifically, a bursty region shows maximum spike in the number of spatial
objects in a given time window. The problem is useful in addressing several
real-world challenges such as surge pricing problem in online transportation
and disease outbreak detection. To solve the problem, we propose an exact
solution and two approximate solutions, and the approximation ratio is
in terms of the burst score, where is a parameter
to control the burst score. We further extend these solutions to support
detection of top- bursty regions. Extensive experiments with real-world data
are conducted to demonstrate the efficiency and effectiveness of our solutions
Universal linear optical operations on discrete phase-coherent spatial modes
Linear optical operations are fundamental and significant for both quantum
mechanics and classical technologies. We demonstrate a non-cascaded approach to
perform arbitrary unitary and non-unitary linear operations for N-dimensional
phase-coherent spatial modes with meticulously designed phase gratings. As
implemented on spatial light modulators (SLMs), the unitary transformation
matrix has been realized with dimensionalities ranging from 7 to 24 and the
corresponding fidelities are from 95.1% to 82.1%. For the non-unitary
operators, a matrix is presented for the tomography of a 4-level quantum system
with a fidelity of 94.9%. Thus, the linear operator has been successfully
implemented with much higher dimensionality than that in previous reports. It
should be mentioned that our method is not limited to SLMs and can be easily
applied on other devices. Thus we believe that our proposal provides another
option to perform linear operation with a simple, fixed, error-tolerant and
scalable scheme
Programmable coherent linear quantum operations with high-dimensional optical spatial modes
A simple and flexible scheme for high-dimensional linear quantum operations
on optical transverse spatial modes is demonstrated. The quantum Fourier
transformation (QFT) and quantum state tomography (QST) via symmetric
informationally complete positive operator-valued measures (SIC POVMs) are
implemented with dimensionality of 15. The matrix fidelity of QFT is 0.85,
while the statistical fidelity of SIC POVMs and fidelity of QST are ~0.97 and
up to 0.853, respectively. We believe that our device has the potential for
further exploration of high-dimensional spatial entanglement provided by
spontaneous parametric down conversion in nonlinear crystals
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