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Physics

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Displaying 1901 - 1925 of 2574

New Improved System for WWVB Broadcast

November 14, 2011
Author(s)
John P. Lowe, Matthew J. Deutch, Glenn K. Nelson, Douglas D. Sutton, William C. Yates, Peder Hansen, Oren Eliezer, Tom Jung, Stephen Morrison, Yingsi Liang, Dinesh Rajan, Sidharth Balasubramanian, Arun Ramasami, Waleed Khalil
The WWVB broadcast of the time-code signal has not undergone major changes in its communications protocol and modulation scheme since its introduction in 1963. Its amplitude-modulation (AM) and pulse-width based representations of its digital symbols were

Synchronizing Computer Clocks by the Use of Kalman Filters

November 14, 2011
Author(s)
Judah Levine
The National Institute of Standards and Technology (NIST) currently operates 35 public network time servers that are located at many different sites in the United States. The servers provide time messages over the public Internet in a number of different

Common-Arm Counter-Propagating Interferometer for Fiber Vibration Measurements

November 1, 2011
Author(s)
Craig W. Nelson, Archita Hati, David A. Howe
We propose and demonstrate a novel technique to measure the vibration sensitivity of two-port fiber-based optical components. It uses a common-arm counter-propagating frequency-shifted interferometer that cancels the vibration induced phase noise of the

A 750 mW, continuous-wave, solid-state laser source at 313 nm for cooling and manipulating trapped 9Be+ ions

October 28, 2011
Author(s)
Andrew C. Wilson, Christian Ospelkaus, Aaron Vandevender, J. A. Mlynek, Kenton R. Brown, Dietrich G. Leibfried, David J. Wineland
We present a solid-state laser system that generates 750 mW of continuous-wave, single frequency, output at 313 nm. Sum-frequency generation with fiber lasers at 1550 nm and 1051 nm produces up to 2 W at 626 nm. This visible light is then converted to UV

Porous Superhydrophobic Membranes: Hydrodynamic Anomaly in Oscillating Flows

October 17, 2011
Author(s)
Sukumar Rajauria, O. Ozsun, John R. Lawall, V. Yakhot, Kamil L. Ekinci
Inspiration for man-made superhydrophobic surfaces comes from Nature: the Lotus leaf [1–3], for instance, exploits superhydrophobicity to keep its surface dry and clean from contaminants. Superhydrophobicity emerges due to roughness on a chemically

Mid-infrared upconversion spectroscopy based on a Yb:fiber frequency laser

October 11, 2011
Author(s)
Scott A. Diddams, Todd Johnson
We present a system for molecular spectroscopy using a mid-infrared broadband frequency comb source with near infrared detection. Difference frequency generation of a Yb:fiber frequency comb produced a mid-infrared (MIR) comb tunable from 2.7 − 4.7 υm

Carbon nanotube arrays for absolute IR and THz radiometry

October 2, 2011
Author(s)
John H. Lehman, Kerry N. Betz, Erich N. Grossman
We have assembled and evaluated a novel electrically calibrated thermopile having an array of 1.5 mm long multiwalled carbon nanotubes as the radiation absorber. We find very low reflectance at the 390 υm laser wavelength and excellent agreement between

The Evolution of Time Measurement, Part 2 - Quartz Clocks

September 30, 2011
Author(s)
Michael Lombardi
A historical article about the origins and the development of quartz clocks and oscillators (Part II of a IV-part series). It describes the discovery of piezoelectricity, the development of the first quartz oscillators, how quartz oscillators were

SEM Induced Shrinking of Solid State Nanopores for Single Molecule Detection

September 22, 2011
Author(s)
Anmiv Prahbu, Kevin J. Freedman, Joseph W. Robertson, Zhorro Nikolov, John J. Kasianowicz, MinJun Kim
We have investigated the shrinkage of solid state nanopores by a scanning electron microscope and find the process to be reproducible and dependant beam parameters such as the accelerating voltage and electron flux. The shrinking phenomenon does not

A Laser-Cooled Frequency Standard for GPS

September 20, 2011
Author(s)
Thomas P. Heavner, Stephan E. Barlow, Marc A. Weiss, Neil Ashby, Steven R. Jefferts
NIST is in an initial phase of developing a prototype laser-cooled atomic frequency standard (AFS) for potential use in a future GPS system. The expected fractional frequency stability or Allan deviation, ς y(τ), will be 2x10 -13 at one second, improving

5 MHz Phase Detector With Low Residual Flicker

September 15, 2011
Author(s)
Corey A. Barnes, Archita Hati, Craig W. Nelson, David A. Howe
The measurement of close-to carrier phase modulation (PM) noise of state-of-the-art oscillators is always challenging. Quite often the residual noise of the phase detector used in these measurements is the source of difficulty. In particular at Fourier

Testing Passive UHF Tag Performance Evolution

September 15, 2011
Author(s)
Daniel G. Kuester, David R. Novotny, Jeffrey R. Guerrieri, Zoya Popovic
Trends in tag development since the introduction of the ISO 18000-6C and EPC Global standards are investigated empirically with measurements of power harvesting and backscattering performance from 20 samples of passive tags across 860-960MHz. The

Chip-scale room-temperature atomic magnetometers for biomedical measurements

September 14, 2011
Author(s)
Svenja A. Knappe, Rahul R. Mhaskar, Jan Preusser, John E. Kitching, Lutz Trahms, Tillman H. Sander
We describe a portable 4-channel array of chip-scale atomic magnetometers in a flexible flying-lead configuration. These microfabricated, uncooled sensors with volumes below 1 cm 3 demonstrate sensitivities around 100 fT/Hz 1/2 and bandwidths of several

Single-qubit-gate error below 10 -4 in a trapped ion

September 14, 2011
Author(s)
Kenton R. Brown, Andrew C. Wilson, Yves Colombe, Christian Ospeklaus, Adam M. Meier, Emanuel H. Knill, Dietrich G. Leibfried, David J. Wineland
In theory, quantum computers can solve certain problems much more efficiently than classical computers [1]. This has motivated experimental efforts to construct and verify devices that manipulate quantum bits (qubits) in a variety of physical systems [2]

Frequency-stabilization to 6x10 -16 via spectral-hole burning

September 11, 2011
Author(s)
Michael J. Thorpe, Tara M. Fortier, Matthew S. Kirchner, Till P. Rosenband, Lars Rippe
We demonstrate two-stage laser stabilization based on a combination of Fabry-Pérot and spectral-hole burning techniques. The laser is first pre-stabilized by the Fabry-Pérot cavity to a fractional-frequency stability of ς y(τ) -13. A pattern of spectral

Near-ground-state transport of trapped-ion qubits through a multidimensional array

September 8, 2011
Author(s)
Dietrich G. Leibfried, Rodney B. Blakestad, Christian Ospelkaus, Aaron Vandevender, Janus Wesenberg, Michael J. Biercuk, David J. Wineland
We have demonstrated transport of 9Be+ ions through a 2D Paul-trap X-junction array while maintaining the ions near the motional ground-state of their local potential well. We expand on the first report of the experiment in [1], including a detailed

State Discriminiation Signal Nulling Receivers

September 6, 2011
Author(s)
Francisco E. Becerra Chavez, Jingyun Fan, Gerald Baumgartner, Sergey V. Polyakov, Julius Goldhar, Jonathan Kosloski, Alan L. Migdall
Optimized state-discrimination receiver strategies for nonorthogonal states can improve the capacity of the communication channels operating with error rates below the ones corresponding to conventional receivers. Coherent signal-nulling receivers use a

p-Wave Cold Collisions in an Optical Lattice Clock

September 2, 2011
Author(s)
Nathan D. Lemke, Andrew D. Ludlow, J. von Stecher, Jeffrey A. Sherman, A.M. Rey, Christopher W. Oates
State-of-the-art optical clocks with neutral atoms employ an optical lattice to tightly confine the atoms, enabling high-resolution spectroscopy and the potential for high-accuracy timekeeping. Interrogating many atoms simultaneously facilitates high

An Interlaboratory Stopwatch Comparison in the SIM Region

September 1, 2011
Author(s)
Michael A. Lombardi, Raul Solis, Harold Sanchez, J. Mauricio Lopez-Romero, Francisco Jimenez, Henry Postigo, Daniel Perez, Walter Adad, Victor Masi, Ahmed Ibrahim, Bill Hoger, Ricardo de Carvalho, Jose L. Kronenberg, Gustavo C. Orozco, Theodore Reddock, Leonardo Trigo
Stopwatches and timers are used for an almost unlimited number of applications and are among the most common devices calibrated by metrology laboratories. In large nations, stopwatch calibrations are typically handled by secondary laboratories, such as

Atomic Sensors - A Review

September 1, 2011
Author(s)
John E. Kitching, Svenja A. Knappe, Elizabeth A. Donley
We discuss the basic physics and instrumentation issues related to high performance physical and inertial sensors based on atomic spectroscopy.

SURF III: A flexible Synchrotron Radiation Source for Radiometry and Research

September 1, 2011
Author(s)
Uwe Arp, Charles W. Clark, Lu Deng, Nadir S. Faradzhev, Alex P. Farrell, Mitchell L. Furst, Steven E. Grantham, Edward W. Hagley, Shannon B. Hill, Thomas B. Lucatorto, Ping-Shine Shaw, Charles S. Tarrio, Robert E. Vest
The calculability of synchrotron radiation (SR) makes electron storage rings wonderful light sources for radiometry. The broadband nature of SR allows coverage of the whole spectral region from the x-ray to the far-infrared. Compact low-energy storage

Offset phase locking of noisy diode lasers aided by frequency division

August 31, 2011
Author(s)
Elizabeth A. Donley, Eugene N. Ivanov, Francois-Xavier R. Esnault
For heterodyne phase locking, frequency division of the beat note between two oscillators can improve the reliability of the phase lock and the quality of the phase synchronization. Frequency division can also reduce the size, weight, power, and cost of
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