# Optical atomic clocks

@article{Ludlow2014OpticalAC,
title={Optical atomic clocks},
author={Andrew D. Ludlow and Martin M. Boyd and Jun Ye and Ekkehard Peik and Piet O Schmidt},
journal={Reviews of Modern Physics},
year={2014},
volume={87},
pages={637-701}
}
• Published 13 July 2014
• Physics
• Reviews of Modern Physics
Optical atomic clocks represent the state-of-the-art in the frontier of modern measurement science. In this article we provide a detailed review on the development of optical atomic clocks that are based on trapped single ions and many neutral atoms. We discuss important technical ingredients for optical clocks, and we present measurement precision and systematic uncertainty associated with some of the best clocks to date. We conclude with an outlook on the exciting prospect for clock…
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## References

SHOWING 1-10 OF 568 REFERENCES
Systematic evaluation of an atomic clock at 2 × 10−18 total uncertainty
• Physics
Nature communications
• 2015
This work performs a new accuracy evaluation of the JILA Sr clock, reducing many systematic uncertainties that limited previous measurements, such as those in the lattice ac Stark shift, the atoms' thermal environment and the atomic response to room-temperature blackbody radiation.
Proceedings of the 6th symposium on frequency standards and metrology : University of St Andrews, Fife, Scotland, 9-14 September 2001
Cold Atom and Cold Trapped Ion Optical & Microwave Frequency Standards Optical Clocks and Atomic Fountain Clocks Optical Combs and Optical Frequency Measurement Microwave and Optical Frequency
Remote atomic clock synchronization via satellites and optical fibers
• Physics
• 2011
Abstract. In the global network of institutions engaged with the realization of International Atomic Time (TAI), atomic clocks and time scales are compared by means of the Global Positioning System
Cryogenic optical lattice clocks with a relative frequency difference of $1\times 10^{-18}$
• Physics
• 2014
Time and frequency are the most accurately measurable quantities, providing foundations for science and modern technologies. The accuracy relies on the SI (Syst\'eme International) second that refers
Optical Lattice Clock with Spin-1/2 Ytterbium Atoms
An Optical Lattice Clock with Spin-1/2 Atoms Report Title An optical lattice clock probes a spectrally narrow electronic transition in an ensemble of optically trapped, lasercooled atoms, for use as
Toward spin squeezing with trapped ions
• Physics
• 2012
Building robust instruments capable ofmaking interferometric measurements with precision beyond the standard quantum limit remains an important goal in many metrology laboratories. We describe here
Direct comparison of optical lattice clocks with an intercontinental baseline of 9000 km.
• Physics
Optics letters
• 2014
A direct frequency comparison between two ⁸⁷Sr lattice clocks operated in intercontinentally separated laboratories in real time confirms the agreement of the two optical frequency standards on an intercontinental scale.
Numerical test of few-qubit clock protocols
The stability of several clock protocols based on 2 to 20 entangled atoms is evaluated numerically by a simulation that includes the effect of decoherence due to classical oscillator noise. In this
Springer handbook of atomic, molecular, and optical physics
Units and Constants.- Part A Mathematical Methods: Angular Momentum Theory.- Group Theory for Atomic Shells.- Dynamical Groups.- Perturbation Theory.- Second Quantization.- Density Matrices.-
Femtosecond Optical Frequency Comb: Principle, Operation and Applications
• Physics
• 2005
Femtosecond Laser Development.- Gigahertz Femtosecond Lasers.- Microstructure Fiber and White-light Generation.- Optical Comb Dynamics and Stabilization.- Femtosecond Noncollinear Parametric