2,834 research outputs found
Optimal cloning of single photon polarization by coherent feedback of beam splitter losses
Light fields can be amplified by measuring the field amplitude reflected at a
beam splitter of reflectivity R and adding a coherent amplitude proportional to
the measurement result to the transmitted field. By applying the quantum
optical realization of this amplification scheme to single photon inputs, it is
possible to clone the polarization states of photons. We show that optimal
cloning of single photon polarization is possible when the gain factor of the
amplification is equal to the inverse squareroot of 1-R.Comment: 10 pages, including 1 figure, extended from letter to full paper, to
be published in New Journal of Physic
Liquid water content and droplet size calibration of the NASA Lewis Icing Research Tunnel
The icing research tunnel at the NASA Lewis Research Center underwent a major rehabilitation in 1986 to 1987, necessitating recalibration of the icing cloud. The methods used in the recalibration, including the procedure used to establish a uniform icing cloud and the use of a standard icing blade technique for measurement of liquid water content are described. PMS Forward Scattering Spectrometer and Optical Array probes were used for measurement of droplet size. Examples of droplet size distributions are shown for several median volumetric diameters. Finally, the liquid water content/droplet size operating envelopes of the icing tunnel are shown for a range of airspeeds and are compared to the FAA icing certification criteria
Comparison of drop size distributions from two droplet sizing systems
A comparison between the Phase Doppler Particle Analyzer and the combined measurements from Particle Measuring Systems' Forward Scattering Spectrometer Probe and the Optical Array Probe was conducted in an icing wind tunnel using NASA Icing Research Tunnel spray nozzles to produce the supercooled water droplet cloud. Clouds having a range of volume median diameters from 10 to greater than 50 microns were used for the instrument comparisons. A volume median diameter was calculated from combining the droplet distributions of the Optical Array Probe and the Forward Scattering Spectrometer Probe. A comparison of the combined volume median diameters and the Phase Doppler Particle Analyzer volume median diameters showed agreement from 10 microns up to 30 microns. Typical drop size distributions from the Phase Doppler Particle Analyzer, the Forward Scattering Spectrometer Probe, and Optical Array Probe are presented for several median volume diameters. A comparison of the distributions illustrates regions of the distributions where there is good agreement and other regions where there are discrepancies between the Phase Doppler Particle Analyzer and the Particle Measuring Systems' droplet size instruments
Performance of the forward scattering spectrometer probe in NASA's icing research tunnel
Two Forward Scattering Spectrometer Probes were used to measure droplet distributions in the NASA Lewis Icing Research Tunnel. The instruments showed good agreement when the median volume diameter (MVD) was approximately 16 micrometers. Coincidence events affect much of the data and caused the measured MVD to be about 2 to 3 micrometers larger than expected. Coincidence events were reduced by shutting down half of the spray bars in the tunnel during certain tests
Gain tuning and fidelity in continuous variable quantum teleportation
The fidelity of continuous variable teleportation can be optimized by
changing the gain in the modulation of the output field. We discuss the gain
dependence of fidelity for coherent, vacuum and one photon inputs and propose
optimal gain tuning strategies for corresponding input selections.Comment: 23 pages, 10 figure
Information extraction and quantum state distortions in continuous variable quantum teleportation
We analyze the loss of fidelity in continuous variable teleportation due to
non-maximal entanglement. It is shown that the quantum state distortions
correspond to the measurement back-action of a field amplitude measurement.
Results for coherent states and for photon number states are presented.Comment: 4 pages Latex, contribution to the proceedings of the ISQM'01
conference held August 27th to 30th in Toky
Fidelity and information in the quantum teleportation of continuous variables
Ideally, quantum teleportation should transfer a quantum state without
distortion and without providing any information about that state. However,
quantum teleportation of continuous electromagnetic field variables introduces
additional noise, limiting the fidelity of the quantum state transfer. In this
article, the operator describing the quantum state transfer is derived. The
transfer operator modifies the probability amplitudes of the quantum state in a
shifted photon number base by enhancing low photon numbers and suppressing high
photon numbers. This modification of the statistical weight corresponds to a
measurement of finite resolution performed on the original quantum state. The
limited fidelity of quantum teleportation is thus shown to be a direct
consequence of the information obtained in the measurement.Comment: 10 pages, including one figure, minor clarifications and added
referenc
The art of spacecraft design: A multidisciplinary challenge
Actual design turn-around time has become shorter due to the use of optimization techniques which have been introduced into the design process. It seems that what, how and when to use these optimization techniques may be the key factor for future aircraft engineering operations. Another important aspect of this technique is that complex physical phenomena can be modeled by a simple mathematical equation. The new powerful multilevel methodology reduces time-consuming analysis significantly while maintaining the coupling effects. This simultaneous analysis method stems from the implicit function theorem and system sensitivity derivatives of input variables. Use of the Taylor's series expansion and finite differencing technique for sensitivity derivatives in each discipline makes this approach unique for screening dominant variables from nondominant variables. In this study, the current Computational Fluid Dynamics (CFD) aerodynamic and sensitivity derivative/optimization techniques are applied for a simple cone-type forebody of a high-speed vehicle configuration to understand basic aerodynamic/structure interaction in a hypersonic flight condition
PowerAqua: fishing the semantic web
The Semantic Web (SW) offers an opportunity to develop novel, sophisticated forms of question answering (QA). Specifically, the availability of distributed semantic markup on a large scale opens the way to QA systems which can make use of such semantic information to provide precise, formally derived answers to questions. At the same time the distributed, heterogeneous, large-scale nature of the semantic information introduces significant challenges. In this paper we describe the design of a QA system, PowerAqua, designed to exploit semantic markup on the web to provide answers to questions posed in natural language. PowerAqua does not assume that the user has any prior information about the semantic resources. The system takes as input a natural language query, translates it into a set of logical queries, which are then answered by consulting and aggregating information derived from multiple heterogeneous semantic sources
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