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Search Publications by: Andrew Ludlow (Fed)

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Displaying 26 - 50 of 117

Towards the optical second: verifying optical clocks at the SI limit

April 11, 2019
Author(s)
William F. McGrew, Xiaogang Zhang, Robert J. Fasano, Holly Leopardi, Daniele Nicolodi, Kyle P. Beloy, Jian Yao, Jeffrey A. Sherman, Stefan A. Schaeffer, Joshua J. Savory, Stefania Romisch, Christopher W. Oates, Thomas E. Parker, Tara M. Fortier, Andrew D. Ludlow
The pursuit of ever more precise measures of time and frequency motivates redefinition of the second in terms of an optical atomic transition. To ensure continuity with the current definition, based on the microwave hyperfine transition in 133Cs, it is

First observation with global network of optical atomic clocks aimed for a dark matter detection

January 30, 2019
Author(s)
P. Wcislo, P. Ablewski, Kyle Beloy, S. Bilicki, M. Bober, Roger Brown, Robert J. Fasano, R. Ciurylo, H. Hachisu, T. Ido, J. Lodewyck, Andrew Ludlow, Will McGrew, P. Morzynski, Daniele Nicolodi, Marco Schioppo, M. Sekido, R. Le Targat, P. Wolf, Xiaogang Zhang, B. Zjawin, M. Zawada
We report on the first earth-scale quantum sensor network based on optical atomic clocks aimed at dark matter (DM) detection. Exploiting differences in the susceptibilities to the fine- structure constant of essential parts of an optical atomic clock, i.e

Atomic clock performance beyond Earths gravitational limit

December 6, 2018
Author(s)
William F. McGrew, Xiaogang Zhang, Robert J. Fasano, Stefan A. Schaeffer, Kyle P. Beloy, Daniele Nicolodi, Roger C. Brown, N. Hinkley, G. Milani, Marco Schioppo, T. H. Yoon, Andrew D. Ludlow
The passage of time is tracked by counting oscillations of a suitable frequency reference (e.g., the number of revolutions of Earth around the sun or the number of swings of a pendulum of a grandfather clock). By referencing the oscillations arising from

A Faraday-shielded, DC Stark-free optical lattice clock

May 2, 2018
Author(s)
Kyle P. Beloy, Xiaogang Zhang, William F. McGrew, Nathan M. Hinkley, Tai H. Yoon, Daniele Nicolodi, Robert J. Fasano, Stefan A. Schaeffer, Roger C. Brown, Andrew D. Ludlow
We demonstrate the absence of a DC Stark shift in an ytterbium optical lattice clock. Stray electric fields are suppressed through the introduction of an in-vacuum Faraday shield. Still, the effectiveness of the shielding must be experimentally assessed

An optical clock to go

May 1, 2018
Author(s)
Andrew D. Ludlow
Bringing next-generation atomic clocks out of the lab is not an easy task, but doing so will unlock many new possibilities. As a crucial first step, a portable atomic clock has now been deployed for relativistic geodesy measurements in the Alps.

Progress on Optical-clock-based Time Scale at NIST: Simulations and Preliminary Real-Data Analysis

April 20, 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

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

Hyperpolarizability and Operational Magic Wavelength in an Optical Lattice Clock

December 19, 2017
Author(s)
Roger C. Brown, Nate B. Phillips, Kyle P. Beloy, William F. McGrew, Marco Schioppo, Robert J. Fasano, Gianmaria Milani, Xiaogang Zhang, Nathan M. Hinkley, Holly F. Leopardi, T H. Yoon, Daniele Nicolodi, Tara M. Fortier, Andrew D. Ludlow
Optical clocks benefit from tight atomic confinement enabling extended interrogation times as well as Doppler- and recoil-free operation. However, these benefits come at the cost of frequency shifts that, if not properly controlled, may degrade clock

Photonic-Chip Supercontinuum with Tailored Spectra for Counting Optical Frequencies

July 24, 2017
Author(s)
David R. Carlson, Daniel D. Hickstein, Alexander J. Lind, Judith B. Olson, Richard W. Fox, Roger C. Brown, Andrew D. Ludlow, Qing Li, Daron A. Westly, Tara M. Fortier, Kartik A. Srinivasan, Scott A. Diddams, Scott B. Papp
Supercontinuum generation using chip-integrated photonic waveguides is a powerful approach for spectrally broadening pulsed laser sources with very low pulse energies and compact form factors. When pumped with a mode-locked laser frequency comb, these

A compact, thermal noise limited reference cavity for ultra-low noise microwave generation

March 23, 2017
Author(s)
Josue Davila-Rodriguez, Frederick N. Baynes, Andrew D. Ludlow, Tara M. Fortier, Holly F. Leopardi, Scott A. Diddams, Franklyn J. Quinlan
A 25 mm long, rigidly-held, ultra-stable optical frequency reference cavity is demonstrated. The cavity spacer has an easy-to-manufacture cylindrical shape which nonetheless exhibits a holding geometry predicted to be first-order insensitive to the

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

Optically referenced broadband electronic synthesizer with 15 digits of resolution

September 5, 2016
Author(s)
Franklyn J. Quinlan, Tara M. Fortier, A. Rolland, Frederick N. Baynes, A. J. Metcalf, Archita Hati, Andrew D. Ludlow, Nathan M. Hinkley, M. Shimizu, Joe Campbell, Scott A. Diddams
Increasing demands in the high tech industry for higher data rates and better synchronization necessitates the development of new wideband and tunable sources with improved noise performance over traditional synthesis based quartz oscillators. Precision

Progress on the Optical Lattice Clock

June 1, 2015
Author(s)
Andrew D. Ludlow, Jun Ye
We summarize recent research in the development of the optical lattice clock, with particular focus on the ytterbium and strontium lattice clocks being developed at NIST and JILA. We highlight recent progress in improving the stability and uncertainty of