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Search Publications by: Jeffrey Sherman (Fed)

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Displaying 26 - 50 of 56

Incorporating an Optical Clock into a Time Scale at NIST: Simulations and Preliminary Real-Data Analysis

March 29, 2018
Author(s)
Jian Yao, Jeffrey A. Sherman, Tara M. Fortier, Thomas E. Parker, Judah Levine, Joshua J. Savory, Stefania Romisch, William F. McGrew, Robert J. Fasano, Stefan A. Schaeffer, Kyle P. Beloy, Andrew D. Ludlow
This paper shows the recent NIST work on incorporating an optical clock into a time scale. We simulate a time scale composed of continuously-operating commercial hydrogen masers and an optical frequency standard that does not operate continuously as a

The effects of the January 2016 UTC offset anomaly on GPS clocks monitored at NIST

January 31, 2017
Author(s)
Jian Yao, Michael A. Lombardi, Andrew N. Novick, Bijunath Patla, Jeffrey A. Sherman, Victor S. Zhang
Errors in the Coordinated Universal Time (UTC) offset parameters broadcast by Global Positioning System (GPS) satellites caused many thousands of GPS clocks to be in error by approximately -13 µs on January 25-26, 2016. The erroneous UTC offset information

Ultra-stable optical clock with two cold-atom ensembles

January 1, 2017
Author(s)
Marco Schioppo, Roger Brown, Will McGrew, Nathan M. Hinkley, Robert J. Fasano, Kyle Beloy, Gianmaria Milani, Daniele Nicolodi, Jeffrey Sherman, Nate B. Phillips, Christopher W. Oates, Andrew Ludlow
Atomic clocks based on optical transitions are the most stable, and therefore precise, timekeepers available. These clocks operate by alternating intervals of atomic interrogation with ‘dead' time required for quantum state preparation and readout. This

Oscillator metrology with software defined radio

May 24, 2016
Author(s)
Jeffrey A. Sherman, Robert Jordens
Analog electrical elements such as mixers, filters, transfer oscillators, isolating buffers, dividers, and even transmission lines contribute technical noise and unwanted environmental coupling in time and frequency measurements. Software defined radio

Usage analysis of a national internet time service

March 8, 2016
Author(s)
Jeffrey A. Sherman, Judah Levine
The Internet Time Service (ITS) at the National Institute of Standards and Technology (NIST) currently receives over 12 billion time requests per day. ITS servers derive their system time from the NIST atomic-referenced timescale and distribute it freely

NIST on a Chip: Realizing SI units with microfabricated alkali vapour cells

October 16, 2015
Author(s)
John E. Kitching, Elizabeth A. Donley, Svenja A. Knappe, Matthew T. Hummon, Argyrios Dellis, Jeffrey A. Sherman, Kartik A. Srinivasan, Vladimir A. Aksyuk, Qiliang Li, Daron A. Westly, Brian J. Roxworthy, Amit Lal
We describe several ways in which microfabricated alkali atom vapour cells might potentially be used to accurately realize a variety of SI units, including the second, the meter, the kelvin, the ampere and the volt, in a compact, low-cost “chip-scale”

Atomic Clock with 1x10 -18 Room-Temperature Blackbody Stark Uncertainty

December 31, 2014
Author(s)
Kyle P. Beloy, Nathan M. Hinkley, Nate B. Phillips, Jeffrey A. Sherman, Marco Schioppo, John H. Lehman, Ari D. Feldman, Leonard M. Hanssen, Christopher W. Oates, Andrew D. Ludlow
The Stark shift due to blackbody radiation (BBR) is a key factor limiting the performance of many atomic frequency standards, with the BBR environment inside the clock apparatus being difficult to characterize at a high level of precision. Here we

An atomic clock with 10 -18 instability

September 13, 2013
Author(s)
Andrew D. Ludlow, Nathan M. Hinkley, Jeffrey A. Sherman, Nate B. Phillips, Marco Schioppo, Nathan D. Lemke, Kyle P. Beloy, M Pizzocaro, Christopher W. Oates
Atomic clocks have been transformational in science and technology, leading to innovations such as global positioning, advanced communications, and tests of fundamental constant variation. Next-generation optical atomic clocks can extend the capability of

Determination of the 5d6s 3D1 state lifetime and blackbody radiation clock shift in Yb

November 29, 2012
Author(s)
Kyle P. Beloy, Jeffrey A. Sherman, Nathan D. Lemke, Nathan M. Hinkley, Christopher W. Oates, Andrew D. Ludlow
The Stark shift of the ytterbium optical clock transition due to room temperature blackbody radiation is dominated by a static Stark effect, which was recently measured to high accuracy [J. A. Sherman et al., Phys. Rev. Lett. 108, 153002 (2012)]. However

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

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

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

Cold-collision-shift cancelation and inelastic scattering in a Yb optical lattice clock

November 28, 2011
Author(s)
Andrew D. Ludlow, Nathan D. Lemke, Jeffrey A. Sherman, Christopher W. Oates, G. Quemener, J. von Stecher, A.M. Rey
Recently, ρ-wave cold collisions were shown to dominate the density-dependent shift of the clock transition frequency in a 171Yb optical lattice clock. Here we demonstrate that by operating such a system at the proper excitation fraction, the cold