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Physics

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Displaying 2126 - 2150 of 2493

A microfabricated photonic magnetometer

October 26, 2008
Author(s)
Jan Preusser, Vladislav Gerginov, Svenja A. Knappe, John E. Kitching
An integrated optically-controlled sensor, suitable for remote, high-sensitivity detection of magnetic fields is presented. The sensor head is free of electrical currents or metal parts, therefore eliminating distortion of the magnetic fields to be

Alpha-Dot or Not: Comparison of Two Single Atom Optical Clocks

October 5, 2008
Author(s)
Till P. Rosenband, David Hume, Chin-Wen Chou, J.C. Koelemeij, A. Brusch, Sarah Bickman, Windell Oskay, Tara M. Fortier, Jason Stalnaker, Scott A. Diddams, Nathan R. Newbury, William C. Swann, Wayne M. Itano, David J. Wineland, James C. Bergquist
Repeated measurements of the frequency ratio of Hg + and Al + single-atom optical clocks over the course of a year yield a constraint on the possible temporal variation of the fine-structure constant a. The time variation of the measured ratio corresponds

Chip-scale atomic devices: precision atomic instruments based on MEMS

October 5, 2008
Author(s)
John E. Kitching, Svenja A. Knappe, Vladislav Gerginov, Vishal Shah, Peter D. Schwindt, Brad Lindseth, Elizabeth A. Donley, Ying-ju Wang, Eleanor Hodby, Matt Eardley, Ricardo Jimenez Martinez, William C. Griffith, Andrew Geraci, Jan Preusser, Tara C. Liebisch, Hugh Robinson, Leo Hollberg
We describe recent work at NIST to develop compact, low-power instruments based on a combination of precision atomic spectroscopy, advanced diode lasers and microelectromechanical systems (MEMS). Designed to be fabricated in parallel in large numbers

NIST F1 and F2

October 5, 2008
Author(s)
Thomas P. Heavner, Tom Parker, Jon H. Shirley, Steven R. Jefferts
The National Institute of Standards and Technology operates a cesium fountain primary frequency standard, NIST-F1, which has been contributing to International Atomic Time (TAI) since 1999. At the time of the last Symposium on Frequency Standards and

Weight Functions for Biases in Atomic Frequency Standards

October 5, 2008
Author(s)
Jon H. Shirley
We present a unified treatment of frequency-standard biases that vary significantly during the time of measurement. We introduce three time-dependent weight functions built from the solution of the unperturbed equations of motion for a two-level system. By

Recent atomic clock comparisions at NIST

October 1, 2008
Author(s)
Luca Lorini, Neil Ashby, Anders Brusch, Scott Diddams, Robert E. Drullinger, Eric Eason, Tara Fortier, Pat Hastings, Thomas P. Heavner, David Hume, Wayne M. Itano, Steven R. Jefferts, Nathan R. Newbury, Tom Parker, Till P. Rosenband, Jason Stalnaker, William C. Swann, David J. Wineland, James C. Bergquist
The record of atomic clock frequency comparisons at NIST over the past half-decade provides one of the tightest constraints of any present-day, temporal variations of the fundamental constants. Notably, the 6-year record of increasingly precise

Ratio of the Al + and Hg + Optical Clock Frequencies to 17 Decimal Places

August 25, 2008
Author(s)
Wayne M. Itano, Till P. Rosenband, David Hume, P.O. Schmidt, Chin-Wen Chou, A. Brusch, Luca Lorini, Windell Oskay, Robert E. Drullinger, Sarah Bickman, Tara M. Fortier, Jason Stalnaker, Scott A. Diddams, William C. Swann, Nathan R. Newbury, David J. Wineland, James C. Bergquist
Frequency standards (atomic clocks) based on narrow optical transitions in 27Al + and 199Hg + have been developed over the past several years at NIST. These two types of standards are both based on single ions confined in Paul traps, but differ in the

Passively mode-locked 10 GHz femtosecond Ti:sapphire laser

August 15, 2008
Author(s)
A Bartels, Dirk Heinecke, Scott Diddams
We report a mode-locked Ti:sapphire femtosecond laser emitting pulses as short as 42 fs at 10 GHz repetition rate. When operated with a spectrally-integrated average power greater than 1 W, the associated femtosecond laser frequency comb (FLFC) contains

Why the long-term charge offset drift in Si single-electron tunneling transistors is much smaller (better) than in metal-based ones: Two-level fluctuator stability

August 7, 2008
Author(s)
Neil M. Zimmerman, W H. Huber, Brian J. Simonds, Emmanouel S. Hourdakis, Fujiwara Fujiwara, Yukinori Ono, Yasuo Takahashi, Hiroshi Inokawa, Miha Furlan, Mark W. Keller
A common observation in metal-based (specifically, those with AlOx tunnel junctions) single- electron tunneling (SET) devices is a time-dependent instability known as the long-term charge offset drift. This drift is not seen in Si-based devices. Our aim is

Quantum Computing With Ions

August 1, 2008
Author(s)
David J. Wineland, C Monroe
This article briefly describes methods to generate entanglement and implement quantum information processing with the use of trapped ions. It is intended to give a simple introduction to the techniques involved, the status of the field and indicate future

Albedo Measurements and Optical Sizing of Single Aerosol Particles

July 31, 2008
Author(s)
Todd J. Sanford, Daniel Murphy, David S. Thomson, Richard W. Fox
Aerosols play an important role in global climate change by their interactions with incoming solar radiation and outgoing longwave radiation from the planetary surface. The climate effects of aerosols depend on their scattering and absorption properties

Spectrally Bright and Broad Fiber-Based Heralded Single-Photon Source

July 29, 2008
Author(s)
Elizabeth A. Goldschmidt, M D. Eisaman, Jingyun Fan, Sergey V. Polyakov, Alan L. Migdall
We present the first experimental characterization of a heralded single-photon source based on spontaneous four-wave-mixing in a single-mode microstructure fiber. We measure the second-order correlation function, g(2)(0), to be far below the classical

Observations of Pt/Ne hollow cathode lamps similar to those used on the Cosmic Origins Spectrograph

July 7, 2008
Author(s)
Gillian Nave, Craig J. Sansonetti, S. V. Penton, Nathaniel Cunningham, Matthew Beasley, Steve Osterman, F Kerber, Charles D. Keyes, Michael R. Rosa
We report accelerated aging tests on three Pt/Ne lamps from the same manufacturing run as lamps installed on the Cosmic Origins Spectrograph (COS). One lamp was aged in air at the National Institute of Standards and Technology (NIST) at a current of 10 mA

Improving Correlations with Inelastic Loss

June 6, 2008
Author(s)
James V. Porto
Correlations are one of the central features of modern condensed matter physics. They arise in systems where the behavior of any given particle in a system depends strongly on all the other particles. Such correlations are what help distinguish the

Astronomical spectrograph calibration with broad-spectrum frequency combs

May 29, 2008
Author(s)
Danielle Braje, Matthew S. Kirchner, Tara M. Fortier, Scott A. Diddams, Leo W. Hollberg, Steve Osterman
Broad-band frequency combs are filtered to spectrographically resolvable frequency-mode spacing, and the limitations of using cavities for spectral filtering are considered. Data and theory are used to show implications to spectrographic calibration of

Optical Microchip Detection of Nuclear Magnetic Resonance

May 4, 2008
Author(s)
M Ledbetter, I Savukov, D Budker, Vishal Shah, Svenja A. Knappe, John Kitching, S Xu, D Michalak, A Pines
We demonstrate optical detection of nuclear magnetic resonance on a microchip. A theoretical optimization indicates detection limits that are competitive with that demonstrated by microcoils in high magnetic fields, without requiring superconducting

Humidity Standard of Compressed Hydrogen for Fuel Cell Technology

May 2, 2008
Author(s)
Peter H. Huang
Compressed hydrogen is one of the most important utilities in fuel cell industry. For the specification of hydrogen fuel quality and for the design of humidification equipment, knowledge of the equilibrium water content of hydrogen as a function of

Shear Thinning Near the Critical Point of Xenon

April 17, 2008
Author(s)
Robert F. Berg, Michael R. Moldover, M Yao, G A. Zimmerli
We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids, near the critical point of xenon. The data span the range of reduced shear rates: 0.001 < γτ < 700, where γτ is the shear rate scaled by the relaxation time τ of

Optical Lattice Induced Light Shifts in a Yb Atomic Clock

March 14, 2008
Author(s)
Zeb Barber, Jason Stalnaker, Nathan D. Lemke, Christopher W. Oates, Tara M. Fortier, Scott A. Diddams, Leo W. Hollberg, C Hoyt
We present an experimental study of the lattice induced light shifts on the $^1S_0\rightarrow\,^3P_0$ clock transition of ytterbium. The ``magic'' frequency for the $^{174}$Yb isotope was determined to be $u_{magic} = 394\,799\,475(35)$MHz. The

Lack of charge offset drift is a robust property of Si single electron transistors

February 12, 2008
Author(s)
Emmanouel S. Hourdakis, J A. Wahl, Neil M. Zimmerman
Single electron transistors (SETs) face several challenges before they can be considered technologically useful devices. One of them is the random, low frequency, charge offset drift that inhibits their use in parallel. Recently, tunable barrier Si SETs

Large-scale MCHF Calculation of the Li I 4d-4f Energy Separation

November 1, 2007
Author(s)
Yuri Ralchenko, Charlotte Fischer
The calculational methods in atomic structure are currently capable of providing the level of accuracy close to that of the most precise experiments. The multiconfiguration Hartree-Fock method is applied to calculation of the 4d--4f energy difference in Li

Passive Cooling of a Micromechanical Oscillator with a Resonant Electric Circuit

September 28, 2007
Author(s)
Kenton R. Brown, Joseph W. Britton, Ryan Epstein, John Chiaverini, Dietrich G. Leibfried, David J. Wineland
Currently there is considerable interest in the cooling of macroscopic mechanical oscillators, as strong cooling may allow one to reach the quantum regime of such oscillators. Recent advances in microfabrication and cooling techniques have brought this
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