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Displaying 1851 - 1875 of 2587

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 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

Resource Letter SS-1: The Spin-Statistics Connection

April 4, 2012
Author(s)
Catalina Curceanu, John Gillaspy, R. C. Hilborn
This Resource Letter provides a guide to the literature on the Spin-Statistics Connection and related issues such as the Pauli Exclusion Principle and particle indistinguishability. Journal articles and books are cited for the following topics: basic

The Evolution of Time Measurement Part V: Radio Controlled Clocks

April 1, 2012
Author(s)
Michael A. Lombardi
A historical article about the origins and the development of radio controlled clocks (Part IV of a IV-part series). It describes the first time signal radio stations, the early use of telegraphic time codes, and the modern use of digital time codes. It

Graphene Carrier Transport Theory

March 31, 2012
Author(s)
Shaffique Adam
In this chapter we study the mechanisms for carrier transport in two dimensional graphene sheets. We demonstrate that at high carrier density, graphene's transport properties depend both on the type of impurities present and on graphene's screening

Quantum interface between an electrical circuit and a single atom

March 30, 2012
Author(s)
Jacob M. Taylor, Dvir Kafri, David Kielpinski, G J. Milburn, M J. Woolley
Atomic systems are remarkably well suited to storage and processing of quantum information. However, their properties are tightly constrained by physical law, causing difficulties in interfacing to optical or electronic devices. On the other hand, quantum
Displaying 1851 - 1875 of 2587
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