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Search Publications by: Youssef S Hassan (Assoc)

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Displaying 1 - 10 of 10

Lattice Light Shift Evaluations In a Dual-Ensemble Yb Optical Lattice Clock

January 22, 2025
Author(s)
Tobias Bothwell, Roger Brown, Benjamin Hunt, Jacob Siegel, Tanner Grogan, Youssef Hassan, Kyle Beloy, Andrew Ludlow, Kurt Gibble, Takumi Kobayashi, Marianna Safronova, Sergey Porsev
In state-of-the-art optical lattice clocks, beyond-electric-dipole polarizability terms lead to a break-down of magic wavelength trapping. In this Letter, we report a novel approach to evaluate lattice light shifts, specifically addressing recent

Ratchet Loading and Multi-Ensemble Operation in an Optical Lattice Clock

August 8, 2024
Author(s)
Youssef Hassan, Takumi Kobayashi, Tobias Bothwell, Jacob Siegel, Benjamin Hunt, Kyle Beloy, Kurt Gibble, Tanner Grogan, Andrew Ludlow
We demonstrate programmable control over the spatial distribution of ultra-cold atoms confined in an optical lattice. The control is facilitated through a combination of spatial manipulation of the magneto-optical trap and atomic population shelving to a

Clock-line-mediated Sisyphus Cooling

July 31, 2024
Author(s)
Jacob Siegel, Benjamin Hunt, Tanner Grogan, Youssef Hassan, Kyle Beloy, Roger Brown, Andrew Ludlow, Chun-Chia Chen, Kurt Gibble
We demonstrate sub-recoil Sisyphus cooling using the long-lived 3P0 clock state in alkaline-earthlike ytterbium. A 1388 -nm optical standing wave nearly resonant with the 3P0→3D1 transition creates a spatially periodic light shift of the 3P0 clock state

Excited-Band Coherent Delocalization for Improved Optical Lattice Clock Performance

March 24, 2024
Author(s)
Jacob Siegel, Andrew Ludlow, Youssef Hassan, Kyle Beloy, Tanner Grogan, Chun-Chia Chen
We implement coherent delocalization as a tool for improving the two primary metrics of atomic clock performance: systematic uncertainty and instability. By decreasing atomic density with co- herent delocalization, we suppress cold-collision shifts and two

Improved interspecies optical clock comparisons through differential spectroscopy

November 28, 2022
Author(s)
May E. Kim, Will McGrew, Nicholas Nardelli, Ethan Clements, Youssef Hassan, Xiaogang Zhang, Jose Valencia, Holly Leopardi, David Hume, Tara Fortier, Andrew Ludlow, David Leibrandt
Comparisons of high-accuracy optical atomic clocks \citeLudlow2015} are essential for precision tests of fundamental physics \citeSafronova2018}, relativistic geodesy \citeMcGrew2018, Grotti2018, Delva2019}, and the anticipated redefinition of the SI

Sub-recoil clock-transition laser cooling enabling shallow optical lattice clocks

September 8, 2022
Author(s)
Xiaogang Zhang, Kyle Beloy, Youssef Hassan, William McGrew, Chun-Chia Chen, Jacob Siegel, Tanner Grogan, Andrew Ludlow
Laser cooling is a key ingredient for quantum control of atomic systems in a variety of settings. In two-valence-electron atoms, two-stage Doppler cooling is typically used to bring atoms to the μK regime. Here, we implement a pulsed radial cooling scheme

Frequency Ratio Measurements with 18-Digit Accuracy Using a Network of Optical Clocks

March 24, 2021
Author(s)
Kyle Beloy, Martha I. Bodine, Tobias B. Bothwell, Samuel M. Brewer, Sarah L. Bromley, Jwo-Sy Chen, Jean-Daniel Deschenes, Scott Diddams, Robert J. Fasano, Tara Fortier, Youssef Hassan, David Hume, Dhruv Kedar, Colin J. Kennedy, Isaac Kader, Amanda Koepke, David Leibrandt, Holly Leopardi, Andrew Ludlow, Will McGrew, William Milner, Daniele Nicolodi, Eric Oelker, Tom Parker, John M. Robinson, Stefania Romisch, Stefan A. Schaeffer, Jeffrey Sherman, Laura Sinclair, Lindsay I. Sonderhouse, William C. Swann, Jian Yao, Jun Ye, Xiaogang Zhang
Atomic clocks occupy a unique position in measurement science, exhibiting higher accuracy than any other measurement standard and underpinning six out of seven base units in the SI system. By exploiting higher resonance frequencies, optical atomic clocks

Measurement of the 27Al+ and 87Sr absolute optical frequencies

January 21, 2021
Author(s)
Holly Leopardi, Kyle Beloy, Tobias B. Bothwell, Samuel M. Brewer, Sarah L. Bromley, Jwo-Sy Chen, Scott Diddams, Robert J. Fasano, Youssef S. Hassan, David B. Hume, Dhruv Kedar, Colin J. Kennedy, Isaac H. Khader, David R. Leibrandt, Andrew D. Ludlow, William F. McGrew, William R. Milner, Daniele Nicolodi, Eric Oelker, Thomas E. Parker, John M. Robinson, Stefania Romisch, Jeffrey A. Sherman, Lindsay I. Sonderhouse, William C. Swann, Jian Yao, Jun Ye, Xiaogang Zhang, Tara M. Fortier
We perform absolute measurement of the 27Al+ single-ion and 87Sr neutral lattice clock frequencies at the National Institute of Standards and Technology and JILA at the University of Colorado against a global ensemble of primary frequency standards. Over

Coherent Optical Clock Down-Conversion for Microwave Frequencies with 10-18 Instability

May 22, 2020
Author(s)
Takuma Nakamura, Josue Davila-Rodriguez, Holly Leopardi, Jeffrey Sherman, Tara Fortier, Xiaojun Xie, Joe C. Campbell, Will McGrew, Xiaogang Zhang, Youssef Hassan, Daniele Nicolodi, Kyle Beloy, Andrew Ludlow, Scott Diddams, Franklyn Quinlan
Optical atomic clocks are poised to redefine the SI second, thanks to stability and accuracy more than one hundred times better than the current microwave atomic clock standard. However, the best optical clocks have not seen their performance transferred

Modeling motional energy spectra and lattice light shifts in optical lattice clocks

May 8, 2020
Author(s)
Kyle Beloy, Will McGrew, Xiaogang Zhang, Daniele Nicolodi, Robert J. Fasano, Youssef Hassan, Roger Brown, Andrew Ludlow
We develop a model to describe the motional (i.e., external degree of freedom) energy spectra of atoms trapped in a one-dimensional optical lattice, taking into account both axial and radial confinement relative to the lattice axis. Our model respects the