National plans for aircraft icing and improved aircraft icing forecasts and associated warning services

Recently, the United States has increased its activities related to aircraft icing in numerous fields: ice phobics, revised characterization of icing conditions, instrument development/evaluation, de-ice/anti-ice devices, simulated supercooled clouds, computer simulation and flight tests. The Federal Coordinator for Meteorology is involved in two efforts, one a National Plan on Aircraft Icing and the other a plan for Improved Aircraft Icing Forecasts and Associated Warning Services. These two plans will provide an approved structure for future U.S. activities related to aircraft icing. The recommended activities will significantly improve the position of government agencies to perform mandated activities and to enable U.S. manufacturers to be competitive in the world market

Fibre imaging bundles for full-field optical coherence tomography

An imaging fibre bundle is incorporated into a full-field imaging OCT system, with the aim of eliminating the mechanical scanning currently required at the probe tip in endoscopic systems. Each fibre within the imaging bundle addresses a Fizeau interferometer formed between the bundle end and the sample, a configuration which ensures down lead insensitivity of the probe fibres, preventing variations in sensitivity due to polarization changes in the many thousand constituent fibres. The technique allows acquisition of information across a planar region with single-shot measurement, in the form of a 2D image detected using a digital CCD camera. Depth scanning components are now confined within a processing interferometer external to the completely passive endoscope probe. The technique has been evaluated in our laboratory for test samples, and images acquired using the bundle-based system are presented. Data are displayed either as en-face scans, parallel to the sample surface, or as slices through the depth of the sample, with a spatial resolution of about 30 ï ­m. The minimum detectable reflectivity at present is estimated to be about 10-3, which is satisfactory for many inorganic samples. Methods of improving the signal-to- noise ratio for imaging of lower reflectivity samples are discuss

Frequency and temporal effects in linear optical quantum computing

Typically linear optical quantum computing (LOQC) models assume that all input photons are completely indistinguishable. In practice there will inevitably be non-idealities associated with the photons and the experimental setup which will introduce a degree of distinguishability between photons. We consider a non-deterministic optical controlled-NOT gate, a fundamental LOQC gate, and examine the effect of temporal and spectral distinguishability on its operation. We also consider the effect of utilizing non-ideal photon counters, which have finite bandwidth and time response.Comment: 10 pages, 9 figures, replaced with published versio

Quantum Metrology in the Kerr Metric

A surprising feature of the Kerr metric is the anisotropy of the speed of light. The angular momentum of a rotating massive object causes co- and counter-propagating light paths to move at faster and slower velocities, respectively as determined by a far-away clock. Based on this effect we derive ultimate quantum limits for the measurement of the Kerr rotation parameter $a$ using a interferometric set up. As a possible implementation, we propose a Mach-Zehnder interferometer to measure the "one-way height differential" time effect. We isolate the effect by calibrating to a dark port and rotating the interferometer such that only the direction dependent Kerr-metric induced phase term remains. We transform to the Zero Angular Momentum Observer (ZAMO) flat metric where the observer see $c=1$. We use this metric and the Lorentz transformations to calculate the same Kerr phase shift. We then consider non-stationary observers moving with the planet's rotation, and find a method for cancelling the additional phase from the classical relative motion, thus leaving only the curvature induced phase.Comment: 9 pages, 7 figures, closest to published versio

Modeling photo-detectors in quantum optics

Photo-detection plays a fundamental role in experimental quantum optics and is of particular importance in the emerging field of linear optics quantum computing. Present theoretical treatment of photo-detectors is highly idealized and fails to consider many important physical effects. We present a physically motivated model for photo-detectors which accommodates for the effects of finite resolution, bandwidth and efficiency, as well as dark-counts and dead-time. We apply our model to two simple well known applications, which illustrates the significance of these characteristics.Comment: 8 pages, 7 figure

Estimating space-time parameters with a quantum probe in a lossy environment

We study the problem of estimating the Schwarzschild radius of a massive body using Gaussian quantum probe states. Previous calculations assumed that the probe state remained pure after propagating a large distance. In a realistic scenario, there would be inevitable losses. Here we introduce a practical approach to calculate the Quantum Fisher Informations (QFIs) for a quantum probe that has passed through a lossy channel. Whilst for many situations loss means coherent states are optimal, we identify certain situations for which squeezed states have an advantage. We also study the effect of the frequency profile of the wavepacket propagating from Alice to Bob. There exists an optimal operating point for a chosen mode profile. In particular, employing a smooth rectangular frequency profile significantly improves the error bound on the Schwarzschild radius compared to a Gaussian frequency profile.Comment: 14 pages, 18 figure

Reading policies for joins: An asymptotic analysis

Suppose that $m_n$ observations are made from the distribution $\mathbf {R}$ and $n-m_n$ from the distribution $\mathbf {S}$. Associate with each pair, $x$ from $\mathbf {R}$ and $y$ from $\mathbf {S}$, a nonnegative score $\phi(x,y)$. An optimal reading policy is one that yields a sequence $m_n$ that maximizes $\mathbb{E}(M(n))$, the expected sum of the $(n-m_n)m_n$ observed scores, uniformly in $n$. The alternating policy, which switches between the two sources, is the optimal nonadaptive policy. In contrast, the greedy policy, which chooses its source to maximize the expected gain on the next step, is shown to be the optimal policy. Asymptotics are provided for the case where the $\mathbf {R}$ and $\mathbf {S}$ distributions are discrete and $\phi(x,y)=1 or 0$ according as $x=y$ or not (i.e., the observations match). Specifically, an invariance result is proved which guarantees that for a wide class of policies, including the alternating and the greedy, the variable M(n) obeys the same CLT and LIL. A more delicate analysis of the sequence $\mathbb{E}(M(n))$ and the sample paths of M(n), for both alternating and greedy, reveals the slender sense in which the latter policy is asymptotically superior to the former, as well as a sense of equivalence of the two and robustness of the former.Comment: Published at http://dx.doi.org/10.1214/105051606000000646 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org