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Physics

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Displaying 2051 - 2075 of 2574

Challenges in SIM to Create a Coordination Program for Time and Frequency

July 26, 2010
Author(s)
J. Mauricio Lopez-Romero, Michael A. Lombardi
The Sistema Interamericano de Metrologia (SIM), one of the world s five major regional metrology organizations (RMOs) recognized by the Bureau International des Poids et Mesures (BIPM), is comprised of national metrology institutes (NMIs) located in all 34

Generation of optical Schrodinger cat states by number-resolved squeezed photon subtraction

July 23, 2010
Author(s)
Thomas Gerrits, Scott C. Glancy, Tracy S. Clement, Brice R. Calkins, Adriana E. Lita, Aaron J. Miller, Alan L. Migdall, Aaron J. Miller, Sae Woo Nam, Richard P. Mirin, Emanuel H. Knill
We have generated and measured an approximation of an optical Schrödinger cat state by photon subtraction from squeezed vacuum. Figure 1 shows the experimental scheme. Photons are probabilistically subtracted from squeezed vacuum and detected with a photon

Ground-based observatory operations optimized and enhanced by direct atmospheric measurements

July 22, 2010
Author(s)
John T. McGraw, Peter C. Zimmer, Azzam Mansour, Dean C. Hines, Anthony B. Hull, Lisa Rossmann, Daniel C. Zirzow, Steven W. Brown, Gerald T. Fraser, Keith R. Lykke, Allan W. Smith, John T. Woodward IV, Christopher W. Stubbs
Earth's atmosphere represents a turbulent, turbid refractive element for every ground-based telescope. We describe the significantly enhanced and optimized operation of observatories supported by the combination of a lidar and spectrophotometer that allows

Hyper-Ramsey spectroscopy of optical clock transitions

July 22, 2010
Author(s)
Christopher W. Oates, V. I. Yudin, A. V. Taichenachev, Zeb Barber, Nathan D. Lemke, Andrew D. Ludlow, U Sterr, Ch. Lisdat, F Riehle
We present nonstandard optical Ramsey schemes that use pulses individually tailored in duration, phase and frequency to cancel spurious frequency shifts related to the excitation itself. In particular, the field shifts and their uncertainties can be

Efficient fiber optic detection of trapped ion flourescence

July 9, 2010
Author(s)
Aaron Vandevender, Yves Colombe, Jason Amini, Dietrich G. Leibfried, David J. Wineland
Integration of fiber optics may play a critical role in the development of quantum information processors based on trapped ions, atoms, and quantum dots. Fibers could help enable a scalable and efficient means of collecting light from and delivering light

Double-Resonance Lineshapes in a Cell with Wall Coating and Buffer Gas

June 28, 2010
Author(s)
Svenja A. Knappe, Hugh Robinson
Microwave double resonances were measured is a wall-coated Rb vapor cell as a function of additional buffer gas pressure. These data were compared to similar measurements in an uncoated cell. It was found that the linewidth in the coated cell displays a

Accurate light-time correction due to a gravitating mass

June 7, 2010
Author(s)
Neil Ashby, Bruno Bertotti
This technical paper of mathematical physics arose as an aftermath of the 2002 Cassini experiment, in which the PPN parameter γ was measured with an accuracy ς γ = 2.3 × 10 -5 and found consistent with the rediction γ=1 of general relativity. The Orbit

High Spectral purity oscillator at 40 GHz: Design using air-dielectric Cavity

June 2, 2010
Author(s)
Archita Hati, Craig W. Nelson, Billy F. Riddle, David A. Howe
We describe the design of a low-PM noise 40 GHz oscillator that uses a conventional air-dielectric cavity resonator as a frequency discriminator to clean up the PM noise of a commercial 10 GHz dielectric resonator oscillator (DRO) multiplied by four. The

Low-Frequency Characterization of MEMS-Based Portable Atomic Magnetometer

June 2, 2010
Author(s)
Rahul R. Mhaskar, Svenja A. Knappe, John E. Kitching
Atomic magnetometers based on absorption or polarization rotation of light in an alkali vapor have recently demonstrated sensitivities rivaling those of superconducting quantum interference devices (SQUIDs). Miniaturization of such devices containing vapor

Medium-Term Frequency Stability of Hydrogen Masers as Measured by a Cesium Fountain

June 2, 2010
Author(s)
Thomas E. Parker, Steven R. Jefferts, Thomas P. Heavner
Abstract Hydrogen masers are used extensively in time scale ensembles, but the frequency drift must be accurately known. NIST-F1, the cesium fountain primary frequency standard at the National Institute of Standards and Technology, now operates nearly

Phase Noise in the Photodetection of Ultrashort Optcial Pulses

June 2, 2010
Author(s)
Jennifer A. Taylor, Franklyn J. Quinlan, Archita Hati, Craig W. Nelson, Scott A. Diddams, Shubahshish Datta, Abhay Joshi
Femtosecond laser frequency combs provide an effective and efficient way to take an ultra-stable optical frequency reference and divide the signal down into the microwave region. In order to convert optical pulses into a usable rf signal, one must use high

Phase noise suppression in frequency comb generators

June 2, 2010
Author(s)
Craig W. Nelson, Archita Hati, J F. Nava-garcia, David A. Howe
We propose an idea to suppress the flicker (1/f) noise in radio frequency (RF) multiplier based frequency comb generators. Comb generators are often used for frequency multiplication in frequency synthesis. In general, comb generators apply high power to a

Towards a compact cold atom frequency standard based on coherent populatoin trapping

June 2, 2010
Author(s)
Francois-Xavier R. Esnault, Elizabeth Donley, John Kitching
We describe in this paper the main features of a cold atom CPT based frequency standard. We explain our particular CPT configuration and our experimental setup. as well as present simulations of the expected performance (stability and major systematics)

Effects of disorder and internal dynamics on vortex wall propagation

May 26, 2010
Author(s)
Hongki Min, Robert D. McMichael, Michael J. Donahue, Jacques Miltat, Mark D. Stiles
Experimental measurements of domain wall propagation are typically interpreted by comparison to ideal models that ignore the effects of extrinsic disorder and the internal dynamics of domain wall structures. Using micromagnetic simulations we study vortex

A common-view disciplined oscillator

May 24, 2010
Author(s)
Michael A. Lombardi, Aaron P. Dahlen
This paper describes a common-view disciplined oscillator (CVDO) that locks to a reference time scale through the use of common-view Global Positioning System (GPS) satellite measurements. A Proportional-Integral-Derivative (PID) controller obtains near

Effect of strain, magnetic field and field angle on the critical current density of YBa 2 Cu 3 O 7-d coated conductors

May 18, 2010
Author(s)
Daniel C. van der Laan, J. F. Douglas, John (Jack) W. Ekin, Loren F. Goodrich, Theodore C. Stauffer, Cameron C. Clickner
A large, magnetic-field-dependent, reversible reduction in critical current density with axial strain in YBa 2Cu 3O 7-δ coated conductors at 75.9 K has been measured. This effect may have important implications for the performance of YBa 2Cu 3O 7-δ coated

Mid-IR frequency comb upconversion spectroscopy

May 16, 2010
Author(s)
Todd Johnson, Scott A. Diddams
We present a mid-infrared frequency comb generated via differency frequency mixing of a Yb femtosecond fiber laser. After passing through a methane gas sample, the MIR comb is upconverted and dispersed onto a CCD for detection.

Preserving quantum coherence using optimized open-loop control techniques

May 16, 2010
Author(s)
Michael J. Biercuk, Hermann Uys, Aaron Vandevender, Nobuyasu Shiga, Wayne M. Itano, John J. Bollinger
We describe experimental and theoretical studies of open-loop quantum control techniques known as dynamical decoupling (DD) for the suppression of decoherence-induced errors in quantum systems. Our experiments on trapped atomic ion qubits demonstrate that

Shell-dependent Blinking of CdSe-Based Core/Shell Nanocrystals

May 10, 2010
Author(s)
Seung Koo Shin, Bonghwan Chon, Sung Jun Lim, Wonjung Kim, Hyeong G. Kang, Taiha Joo, Jeeseong C. Hwang
Blinking of zinc-blende CdSe-based core/shell nanocrystals are studied as a function of shell materials. CdSe/ZnS, CdSe/ZnSe/ZnS, and CdSe/CdS/ZnS core/shell nanocrystals are prepared by epitaxial growth of two-to-six monolayers (MLs) of shell materials

Comparison of Air Kerma and Absorbed Dose to Water Measurements of Co-60 Radiation Beams in Radiotherapy

April 30, 2010
Author(s)
Ronaldo Minniti, I. Csete, A.G. Leiton, V. Sochor, A. Lapenas, J.-E Grindborg, I Jokelainen, H. Bjerke, J. Dobrovodsky, A. Megzifene, H.J. Costas, R. Ivanov, B. Vekic, J. Kokocinski, H.J. Cardoso, L. Buermann, W. Tiefenboeck, G. Stucki, E. van Dijk , M P. Toni, J.P. McCaffrey, C.N.M. da Silva, I Kharitonov, D. Webb, M Saravi, F. Delaunay
The results of the 25 participants of the EUROMET.RI(I)-K1 and EUROMET.RI(I)-K4 key comparisons are reported to support their relevant CMC claims being published or going to be published by the participant laboratories. The measured quantities were the air
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