Spatial and temporal filtering of a 10-W Nd:YAG laser with a Fabry-Perot ring-cavity premode cleaner

We report on the use of a fixed-spacer Fabry–Perot ring cavity to filter spatially and temporally a 10-W laser-diode-pumped Nd:YAG master-oscillator power amplifier. The spatial filtering leads to a 7.6-W TEMinfinity beam with 0.1% higher-order transverse mode content. The temporal filtering reduces the relative power fluctuations at 10 MHz to 2.8 x 10^-/sqrtHz, which is 1 dB above the shot-noise limit for 50 mA of detected photocurrent

The Conflict Between Free Access to Information and the use of Filtering Techniques in Light of the Yahoo Case

The exponential growth and explosion of Information on the Internet has given rise to several questions of socio-economic, political and legal nature, especially as regard to the issue of free access to information and possible limitations to this free use. Since the Internet is a global operating network exceeding therefore national territories, the problem of universal jurisdiction rises. The introduction of filtering techniques has been introduced to deal with this problem. However the use of filtering techniques poses several problems as well and can clearly have a chilling effect on free speech as well.Zadanie pt. „Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki” nr 885/P-DUN/2014 zostało dofinansowane ze środków MNiSW w ramach działalności upowszechniającej nauk

Methods of using carbon nanotubes as filter media to remove aqueous heavy metals

Although carbon nanotubes (CNTs) are well known to have a strong affinity to various heavy metals in aqueous solution, little research has been dedicated to exploit their use in fixed-bed water treatment systems (e.g., trickling filters). In this work, batch sorption and fixed-bed experiments were conducted to examine the ability of functionalized multi-walled CNTs as filter media to remove two heavy metal ions (Pb2+ and Cu2+) from infiltrating water. Batch sorption experiments confirmed the strong sorption affinity of the CNTs for Pb2+ and Cu2+ in both single and dual metal solution systems. In addition, sonication-promoted dispersion of the CNT particles enhanced their heavy metal sorption capacity by 23.9–32.2%. For column experiments, laboratory-scale fixed-bed columns were packed with CNTs and natural quartz sand by three different packing: layered, mixed, and deposited. While all the three packing methods enhanced the fixed-bed filtering efficiency of Pb2+ and Cu2+ from single and dual metal systems, the CNT-deposited packing method was superior. Although the amount of the CNTs added into the fixed-bed columns was only 0.006% (w/w) of the sand, they significantly improved the fixed-bed’s filtering efficiency of Pb2+ and Cu2+ by 55–75% and 31–57%, respectively. Findings from this study demonstrate that functionalized multi-walled CNTs, together with natural sand, can be used to effectively and safely remove heavy metals from water

Wavepacket Dynamics in One-Dimensional System with Long-Range Correlated Disorder

We numerically investigate dynamical property in the one-dimensional tight-binding model with long-range correlated disorder having power spectrum $1/f^\alpha$ ($\alpha:$spectrum exponent) generated by Fourier filtering method. For relatively small $\alpha<\alpha_c(=2)$ time-dependence of mean square displacement (MSD) of the initially localized wavepacket shows ballistic spread and localizes as time elapses. It is shown that $\alpha-$dependence of the dynamical localization length (DLL) determined by the MSD exhibits a simple scaling law in the localization regime for the relatively weak disorder strength $W$. Furthermore, scaled MSD by the DLL almost obeys an universal function from the ballistic to the localization regime in the various combinations of the parameters $\alpha$ and $W$.Comment: 4 pages, 4 figure

Stabilized lasers for advanced gravitational wave detectors

Second generation gravitational wave detectors require high power lasers with more than 100 W of output power and with very low temporal and spatial fluctuations. To achieve the demanding stability levels required, low noise techniques and adequate control actuators have to be part of the high power laser design. In addition feedback control and passive noise filtering is used to reduce the fluctuations in the so-called prestabilized laser system (PSL). In this paper, we discuss the design of a 200 W PSL which is under development for the Advanced LIGO gravitational wave detector and will present the first results. The PSL noise requirements for advanced gravitational wave detectors will be discussed in general and the stabilization scheme proposed for the Advanced LIGO PSL will be described

W-jet Tagging: Optimizing the Identification of Boosted Hadronically-Decaying W Bosons

A method is proposed for distinguishing highly boosted hadronically decaying W's (W-jets) from QCD-jets using jet substructure. Previous methods, such as the filtering/mass-drop method, can give a factor of ~2 improvement in S/sqrt(B) for jet pT > 200 GeV. In contrast, a multivariate approach including new discriminants such as R-cores, which characterize the shape of the W-jet, subjet planar flow, and grooming-sensitivities is shown to provide a much larger factor of ~5 improvement in S/sqrt(B). For longitudinally polarized W's, such as those coming from many new physics models, the discrimination is even better. Comparing different Monte Carlo simulations, we observe a sensitivity of some variables to the underlying event; however, even with a conservative estimates, the multivariate approach is very powerful. Applications to semileptonic WW resonance searches and all-hadronic W+jet searches at the LHC are also discussed. Code implementing our W-jet tagging algorithm is publicly available at http://jets.physics.harvard.edu/wtagComment: Version to appear in PR

Method of measurements with random perturbation: Application in photoemission experiments

We report an application of a simultaneous perturbation stochastic approximation (SPSA) algorithm to filtering systematic noise (SN) with non-zero mean value in photoemission data. In our analysis we have used a series of 50 single-scan photoemission spectra of W(110) surface where randomly chosen SN was added. It was found that the SPSA-evaluated spectrum is in good agreement with the spectrum measured without SN. On the basis of our results a wide application of SPSA for evaluation of experimental data is anticipated.Comment: 11 pages, 3 figure

A look at motion in the frequency domain

A moving image can be specified by a contrast distribution, c(x,y,t), over the dimensions of space x,y, and time t. Alternatively, it can be specified by the distribution C(u,v,w) over spatial frequency u,v and temporal frequency w. The frequency representation of a moving image is shown to have a characteristic form. This permits two useful observations. The first is that the apparent smoothness of time-sampled moving images (apparent motion) can be explained by the filtering action of the human visual system. This leads to the following formula for the required update rate for time-sampled displays. W(c)=W(l)+ru(l) where w(c) is the required update rate in Hz, W(l) is the limit of human temporal resolution in Hz, r is the velocity of the moving image in degrees/sec, and u(l) is the limit of human spatial resolution in cycles/deg. The second observation is that it is possible to construct a linear sensor that responds to images moving in a particular direction. The sensor is derived and its properties are discussed

Multipartite entanglement in 2 x 2 x n quantum systems

We classify multipartite entangled states in the 2 x 2 x n (n >= 4) quantum system, for example the 4-qubit system distributed over 3 parties, under local filtering operations. We show that there exist nine essentially different classes of states, and they give rise to a five-graded partially ordered structure, including the celebrated Greenberger-Horne-Zeilinger (GHZ) and W classes of 3 qubits. In particular, all 2 x 2 x n-states can be deterministically prepared from one maximally entangled state, and some applications like entanglement swapping are discussed.Comment: 9 pages, 3 eps figure

Effect of weak measurement on entanglement distribution over noisy channels

Being able to implement effective entanglement distribution in noisy environments is a key step towards practical quantum communication, and long-term efforts have been made on the development of it. Recently, it has been found that the null-result weak measurement (NRWM) can be used to enhance probabilistically the entanglement of a single copy of amplitude-damped entangled state. This paper investigates remote distributions of bipartite and multipartite entangled states in the amplitudedamping environment by combining NRWMs and entanglement distillation protocols (EDPs). We show that the NRWM has no positive effect on the distribution of bipartite maximally entangled states and multipartite Greenberger-Horne-Zeilinger states, although it is able to increase the amount of entanglement of each source state (noisy entangled state) of EDPs with a certain probability. However, we find that the NRWM would contribute to remote distributions of multipartite W states. We demonstrate that the NRWM can not only reduce the fidelity thresholds for distillability of decohered W states, but also raise the distillation efficiencies of W states. Our results suggest a new idea for quantifying the ability of a local filtering operation in protecting entanglement from decoherence.Comment: 15 pages, 9 figures. Minor revision has been mad