Temperature and humidity profiles in the atmosphere from spaceborne lasers: A feasibility study

Computer simulations of the differential absorption lidar technique in a space craft for the purpose of temperature and humidity profiling indicate: (1) Current technology applied to O2 and H2O lines in the .7 to .8 micrometers wavelength band gives sufficiently high signal-to-noise ratios (up to 50 for a single pulse pair) if backscattering by aerosol particles is high, i.e. profiling accurate to 2 K for temperature and 10% for humidity should be feasible within the turbid lower troposphere in 1 km layers and with an averaging over approximately 100 pulses. (2) The impact of short term fluctuations in aerosol particle concentration is too big for a one laser system. Only a two laser system firing at a time lag of about 1 millisecond can surmount these difficulties. (3) The finite width of the laser line and the quasi-random shift of this line introduce tolerable, partly systematic errors

Experimental Implementation of a Codeword Stabilized Quantum Code

A five-qubit codeword stabilized quantum code is implemented in a seven-qubit system using nuclear magnetic resonance (NMR). Our experiment implements a good nonadditive quantum code which encodes a larger Hilbert space than any stabilizer code with the same length and capable of correcting the same kind of errors. The experimentally measured quantum coherence is shown to be robust against artificially introduced errors, benchmarking the success in implementing the quantum error correction code. Given the typical decoherence time of the system, our experiment illustrates the ability of coherent control to implement complex quantum circuits for demonstrating interesting results in spin qubits for quantum computing

Multiparticle entanglement purification for graph states

We introduce a class of multiparticle entanglement purification protocols that allow us to distill a large class of entangled states. These include cluster states, GHZ states and various error correction codes all of which belong to the class of two-colorable graph states. We analyze these schemes under realistic conditions and observe that they are scalable, i.e. the threshold value for imperfect local operations does not depend on the number of parties for many of these states. When compared to schemes based on bipartite entanglement purification, the protocol is more efficient and the achievable quality of the purified states is larger. As an application we discuss an experimental realization of the protocol in optical lattices which allows one to purify cluster states.Comment: 4 pages, 2 figures; V2: some typos corrected; V3: published versio

Possible climatic effects of contrails and additional water vapour

The importance of contrails in the upper troposphere and of additional water vapour in the lower stratosphere, both the result of aircraft emissions, for the radiation budget of the surface/atmosphere system is roughly assessed. The radiation flux density profiles with contrails and additional water vapour are compared to other greenhouse gas forcings. This leads to a very first order of magnitude estimate of the air traffic climate forcing potential: two percent contrail cover or air traffic induced natural cirrus may be as important for the planetary radiation budget as a 10 percent increase of present anthropogenic CO2 forcing, equivalent to six years emission of 25 Gigatons CO2 per year; additional water vapour in the lowest high northern latitude stratosphere is considerably contributing to the greenhouse effect of the atmosphere. If air traffic would cause a 10 percent increase in water vapour there this would be equivalent to up to 0.2 Wm-2 radiation budget change depending on surface temperature

Extraction of surface temperature from satellite data

Surface temperature figures in nearly all equations for energy fluxes through a surface element. It is routinely derived from satellite radiances over the oceans. However, over land the changing surface emissivity, strong daytime heating as well as nighttime cooling and the difficulty of defining surface temperature for a canopy, have prevented a routine application. This paper shows the possible influences of water vapour content, near surface thermal structure, aerosol particles, thin clouds, slant paths and surface emissivity on the correction of atmospheric masking. A procedure for land surface temperature determination for the NOAA 7, 9 satellite data is put foward. -from Autho

The dependence of the measured cool skin of the ocean on wind stress and total heat flux

The temperature drop δT between the ocean surface and the 5-cm depth was recorded during GATE, Phase III. With measured values of the total heat flux Q and an assumption about the thickness of the viscous boundary layer of the ocean, the wind-speed dependence of the factor of proportionality between δT and Q is determined. This factor depends on the deviations of the thickness of the conductive layer from the thickness of the viscous layer and possibly partially on the wind stress. A further assumption about the thickness of the conductive layer leads to a wind-speed dependence of the ratio between total wind stress and its wave supporting part of it. This ratio increases from a value 1.5 at 1 m s-1 to 9 at 10 m s-1, which is in agreement with existing estimates. © 1976 D. Reidel Publishing Company

On local invariants of pure three-qubit states

We study invariants of three-qubit states under local unitary transformations, i.e. functions on the space of entanglement types, which is known to have dimension 6. We show that there is no set of six independent polynomial invariants of degree less than or equal to 6, and find such a set with maximum degree 8. We describe an intrinsic definition of a canonical state on each orbit, and discuss the (non-polynomial) invariants associated with it.Comment: LateX, 13 pages. Minor typoes corrected. Published versio