3,695 research outputs found
Quantum Illumination at the Microwave Wavelengths
Quantum illumination is a quantum-optical sensing technique in which an
entangled source is exploited to improve the detection of a low-reflectivity
object that is immersed in a bright thermal background. Here we describe and
analyze a system for applying this technique at microwave frequencies, a more
appropriate spectral region for target detection than the optical, due to the
naturally-occurring bright thermal background in the microwave regime. We use
an electro-optomechanical converter to entangle microwave signal and optical
idler fields, with the former being sent to probe the target region and the
latter being retained at the source. The microwave radiation collected from the
target region is then phase conjugated and upconverted into an optical field
that is combined with the retained idler in a joint-detection quantum
measurement. The error probability of this microwave quantum-illumination
system, or quantum radar, is shown to be superior to that of any classical
microwave radar of equal transmitted energy.Comment: In press on Physical Review Letters. Long version of the manuscript,
including both the Letter and the Supplemental Material (15 pages total
Matched direction detectors and estimators for array processing with subspace steering vector uncertainties
In this paper, we consider the problem of estimating and detecting a signal whose associated spatial signature is known to lie in a given linear subspace but whose coordinates in this subspace are otherwise unknown, in the presence of subspace interference and broad-band noise. This situation arises when, on one hand, there exist uncertainties about the steering vector but, on the other hand, some knowledge about the steering vector errors is available. First, we derive the maximum-likelihood estimator (MLE) for the problem and compute the corresponding Cramer-Rao bound. Next, the maximum-likelihood estimates are used to derive a generalized likelihood ratio test (GLRT). The GLRT is compared and contrasted with the standard matched subspace detectors. The performances of the estimators and detectors are illustrated by means of numerical simulations
Inter-satellite Quantum Key Distribution at Terahertz Frequencies
Terahertz (THz) communication is a topic of much research in the context of
high-capacity next-generation wireless networks. Quantum communication is also
a topic of intensive research, most recently in the context of space-based
deployments. In this work we explore the use of THz frequencies as a means to
achieve quantum communication within a constellation of micro-satellites in
Low-Earth-Orbit (LEO). Quantum communication between the micro-satellite
constellation and high-altitude terrestrial stations is also investigated. Our
work demonstrates that THz quantum entanglement distribution and THz quantum
key distribution are viable deployment options in the micro-satellite context.
We discuss how such deployment opens up the possibility for simpler integration
of global quantum and wireless networks. The possibility of using THz
frequencies for quantum-radar applications in the context of LEO deployments is
briefly discussed.Comment: 7 pages, 6 figure
Study to investigate and evaluate means of optimizing the Ku-band combined radar/communication functions for the space shuttle
The Ku band radar system on the shuttle orbiter operates in both a search and a tracking mode, and its transmitter and antennas share time with the communication mode in the integrated system. The power allocation properties and the Costa subloop subcarrier tracking performance associated with the baseline digital phase shift implementation of the three channel orbiter Ku band modulator are discussed
Matched direction detectors
In this paper, we address the problem of detecting a signal whose associated spatial signature is subject to uncertainties, in the presence of subspace interference and broadband noise, and using multiple snapshots from an array of sensors. To account for steering vector uncertainties, we assume that the spatial signature of interest lies in a given linear subspace H while its coordinates in this subspace are unknown. The generalized likelihood ratio test (GLRT) for the problem at hand is formulated. We show that the GLRT amounts to searching for the best direction in the subspace H after projecting out the interferences. The distribution of the GRLT under both hypotheses is derived and numerical simulations illustrate its performance
Meteorological measurements, Satellite PL Quarterly report, 1 Jun. - 31 Aug. 1968
Development of balloon-borne miniature radio altimeter and investigation of multiple array infrared imaging from synchronous satellite
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