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Physics

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Displaying 1751 - 1775 of 2493

Sub-femtosecond absolute timing jitter with a 10 GHz hybrid photonic-microwave oscillator

June 7, 2012
Author(s)
Tara M. Fortier, Craig W. Nelson, Archita Hati, Franklyn J. Quinlan, Jennifer A. Taylor, Haifeng (. Jiang, Chin-Wen Chou, Till P. Rosenband, Nathan D. Lemke, Andrew D. Ludlow, David A. Howe, Christopher W. Oates, Scott A. Diddams
We present an optical-electronic approach to generating microwave signals with high spectral purity. By overcoming shot noise and operating near fundamental thermal limits, we demonstrate 10 GHz signals that have timing deviation from an ideal periodic

Three-dimensional real-time tracking of nanoparticles at an oil-water interface

June 5, 2012
Author(s)
Kan K. Du, James A. Liddle, Andrew J. Berglund
We show that real-time feedback control can be used to study three-dimensional nanoparticle transport dynamics. We apply the method to study the behavior of adsorbed nanoparticles at a silicone oil-water interface in a microemulsion system over a range of

Spectroscopy and Thermometry of Drumhead Modes in a Mesoscopic Trapped-Ion Crystal Using Entanglement

May 25, 2012
Author(s)
Brian C. Sawyer, Joseph W. Britton, Adam Keith, C.-C Joseph Wang, James K. Freericks, Hermann Uys, Michael Biercuk, John J. Bollinger
We demonstrate a method of sensitive detection and thermometry of individual modes in cold ( sim1 mK), planar one-component ion plasmas. Exploiting precise control over the valence electron spins of several hundred crystallized 9Be + confined in a Penning

A Compact Cold-Atom Frequency Standard Based on Coherent Population Trapping

May 24, 2012
Author(s)
Francois-Xavier R. Esnault, John Kitching, Elizabeth Donley
We present the status of our cold-atom clock based on coherent population trapping, including the present clock stability and a preliminary evaluation of the three main systematic frequency shifts: the 1st-order Doppler shift, the Zeeman shift, and the

A high stability optical frequency reference based on thermal calcium atoms

May 24, 2012
Author(s)
Richard W. Fox, Jeffrey Sherman, W. Douglas, Judith B. Olson, Andrew Ludlow, Christopher W. Oates
Here we report an imprecision below 10 -14 with a simple, compact optical frequency standard based upon thermal calcium atoms. Using a Ramsey-Borde spectrometer we excite features with linewidths 5 kHz for the 1S 0- 3P 1 intercombination line at 657 nm

A hybrid 10 GHz photonic-microwave oscillator with sub-femtosecond absolute timing jitter

May 24, 2012
Author(s)
Tara M. Fortier, Craig W. Nelson, Archita Hati, Franklyn J. Quinlan, Jennifer A. Taylor, Haifeng (. Jiang, Chin-Wen Chou, Nathan D. Lemke, Andrew D. Ludlow, David A. Howe, Christopher W. Oates, Scott A. Diddams
We demonstrate a 10 GHz hybrid oscillator comprised of a phase stabilized optical frequency comb divider and a room temperature dielectric sapphire oscillator. Characterization of the 10 GHz microwave signal via comparison of two independent hybrid

A new algorithm for clock weights for the SIM time scale

May 24, 2012
Author(s)
Michael A. Lombardi, J. Mauricio Lopez-Romero, Nelida Diaz-Munoz, E. de Carlos-Lopez
A time and frequency comparison system has been developed for the Sistema Interamericano de Metrologia (SIM) region in order to compare in real time the time references maintained at the SIM national metrology institutes (NMIs). Since January 2010 a

A Sub-Sampling Digital PM/AM Noise Measurement System

May 24, 2012
Author(s)
Craig W. Nelson, David A. Howe
A digital phase/amplitude modulation (PM/AM) noise measurement system (DNMS) implementing field programmable gate array (FPGA) based digital down converters (DDCs), and 250 MHz analog to digital converters (ADCs) is reported. Performance in the first

Blackbody effects in the Yb optical lattice clock

May 24, 2012
Author(s)
Andrew D. Ludlow, Jeffrey A. Sherman, Nathan D. Lemke, Kyle P. Beloy, Nathan M. Hinkley, M. Pizzocaro, Richard W. Fox, Christopher W. Oates
We report a high accuracy measurement of the differential static polarizability for the clock transition in a Yb lattice clock, a key parameter for determining the blackbody BBR) shift of this transition. We further report efforts to determine the 6s5d3D1

Common-Arm Counter Propagating Phase Bridge for Vibration Sensitivity Measurement

May 24, 2012
Author(s)
Danielle G. Lirette, Corey A. Barnes, Archita Hati, Jason A. DeSalvo, Craig W. Nelson, David A. Howe
Current methods for measuring the vibration sensitivity of microwave devices are primarily limited by choice of cables connecting a stationary platform to a vibrating actuator. We experimentally compare the current ("conventional") method with a new (

Mechanical stabilization of a microrod-resonator optical frequency

May 24, 2012
Author(s)
Scott B. Papp, Pascal P. Del'Haye, Scott A. Diddams
We present line-spacing frequency control of a microresonator-based optical frequency comb by way of mechanical actuation. Using this novel technique we have achieved a record level of residual stability in the line spacing of 5 × 10 -15 for 1s averaging

Phase-Noise Measurement of a 670 GHz Source

May 24, 2012
Author(s)
Jason A. DeSalvo, Archita Hati, Craig W. Nelson, David A. Howe
We present phase-noise measurements in support of terahertz electronics. Using digital phase-noise measurement techniques and an even-harmonic mixer, we achieve a phase-noise measurement system in waveguide (WR1.5). At 670 GHz an upper bound of this system

PM-AM Correlation Measurements and Analysis

May 24, 2012
Author(s)
David A. Howe, Archita Hati, Craig W. Nelson, Danielle G. Lirette
We measure and analyze effects of nonlinear mixing of phase-noise modulation (PM) and amplitude-noise modulation (AM) in an oscillating signal by real-time correlations measured in the cross power spectral density (CPSD). We outline sensitive measurements

Ultra-low-noise Regenerative Frequency Divider for High Spectral Purity RF Signal Generation

May 24, 2012
Author(s)
Archita Hati, Craig W. Nelson, Corey A. Barnes, Danielle G. Lirette, Jason A. DeSalvo, Tara M. Fortier, Franklyn J. Quinlan, Andrew D. Ludlow, Till P. Rosenband, Scott A. Diddams, David A. Howe
We implement an ultra-low-noise frequency divider chain from 8 GHz to 5 MHz that utilizes custom-built regenerative frequency divide-by-2 circuits. The single-sideband (SSB) residual phase noise of this regenerative divider at 5 MHz output is -163 dBc/Hz

Vibrational analysis of stabilized lasers

May 24, 2012
Author(s)
Kenneth J. Hughes, Archita Hati, Craig W. Nelson, David A. Howe
Frequency-stabilized lasers are routinely used in a variety of research and application areas relating to laser-cooled atoms. Important applications in the cold-atom regime include atomic time keeping, inertial navigation, gravitational sensing, and

Real-time measurements of plasma photoresist modifications: The role of plasma vacuum ultraviolet radiation and ions

May 23, 2012
Author(s)
Weilnboeck Florian, Nirav Kumar, Gottlieb Oehrlein, Ting-Ying Chung, D Graves, Mingqi Li, Eric A. Hudson, Eric C. Benck
Plasma-induced roughness development of photoresist (PR) can be due to synergistic interactions of surface modifications introduced by ions, bulk material modifications by ultraviolet (UV)/vacuum ultraviolet (VUV) radiation, and increased temperature

Overview of Recent Atomic Spectroscopy At The NIST EBIT

May 5, 2012
Author(s)
John Gillaspy
Seven papers published by the NIST EBIT spectroscopy team and collaborators from mid-2009 to mid-2011 are summarized. Previous discussions of the D-lines in Na-like ions and the Lyman-alpha lines in H-like ions are updated with new information. Nine issues

Engineered two-dimensional Ising interactions on a trapped-ion quantum simulator with hundreds of spins

April 26, 2012
Author(s)
Joseph W. Britton, Brian C. Sawyer, Adam Keith, C.-C. Joseph Wang, James K. Freericks, Hermann Uys, Michael Biercuk, John J. Bollinger
The presence of long-range quantum spin correlations underlies a variety of physical phenomena in condensed matter systems, potentially including high-temperature superconductivity, making this a fertile area for exploration. Unfortunately, many properties

Automated Clock Comparisons and Time Scale Generation in the SIM Region

April 21, 2012
Author(s)
Michael A. Lombardi, J. Mauricio Lopez-Romero, Nelida Diaz-Munoz
The second, the base unit of time interval in the International System, is defined in terms of the two hyperfine states of the Cesium atom ground energy level. This definition has so far served the metrology community well, and the uncertainty of the best

Matrix-based color measurement corrections of tristimulus colorimeters

April 20, 2012
Author(s)
George P. Eppeldauer, Z. T. Kosztyan, J. D. Schanda
For image taking colorimetry the tristimulus technique is still the best practical method to keep the measurement time within reasonable limits. However, the achievable color measurement uncertainties for special sources can be significant because of the

Magnetoencephalography with a chip-scale atomic magnetometer

April 17, 2012
Author(s)
Svenja A. Knappe, Tillman H. Sander, Jan Preusser, Rahul R. Mhaskar, John E. Kitching, Lutz Trahms
We report on the measurement of somatosensory-evoked and spontaneous magnetoencephalography signals with a chip-scale atomic magnetometer. This uncooled, fiber-coupled sensor has a sensitive volume of 0.58 mm 3 inside a sensor head of volume 1 cm 3. When

High-Accuracy Measurement of Atomic Polarizability in an Optical Lattice Clock

April 13, 2012
Author(s)
Jeffrey A. Sherman, Nathan D. Lemke, Nathan M. Hinkley, M. Pizzocaro, Richard W. Fox, Andrew D. Ludlow, Christopher W. Oates
Presently, the Stark effect contributes the largest source of uncertainty in a ytterbium optical atomic clock through blackbody radiation. By employing an ultracold, trapped atomic ensemble and high stability optical clock, we characterize the quadratic
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