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Accurate timekeeping capabilities of atomic clocks are used for navigation by satellite networks such as the European Union's Galileo Program and the United States' GPS.

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Atomic clocks proposed the concept in 1945, which led to a demonstration of a clock based on ammonia in 1949.

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Timekeeping researchers are currently working on developing an even more stable atomic reference for the second, with a plan to find a more precise definition of the second as atomic clocks improve based on optical clocks or the Rydberg constant around 2030.

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Optical Atomic clocks that are as accurate as the most accurate caesium Atomic clocks available, that is with a relative uncertainty of 10, are now being further developed.

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Optical Atomic clocks are a very active area of research in the field of metrology as scientists work to develop Atomic clocks based on elements ytterbium, mercury, aluminum, and strontium.

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In order for this to occur, optical Atomic clocks must be capable of measuring time to very high precision consistently.

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Metrologists are currently designing atomic clocks that implement new developments such as ion traps, and optical combs to reach greater accuracies.

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Time readings of Atomic clocks operated in metrology labs operating with the BIPM need to be known very accurately.

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Some operations require synchronization of atomic clocks separated by great distances over thousands of kilometers.

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Atomic clocks are used to broadcast time signals in the United States Global Positioning System, the Russian Federation's Global Navigation Satellite System, the European Union's Galileo system and China's BeiDou system.

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Caesium Atomic clocks include the NIST-F1 clock, developed in 1999, and the NIST-F2 clock, developed in 2013.

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Atomic clocks based on rubidium standards are therefore regarded as secondary representations of the second.

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Atomic clocks based on hydrogen standards are therefore regarded as secondary representations of the second.

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Atomic clocks resonance has a much higher Q than mechanical devices.

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Atomic clocks can be isolated from environmental effects to a much higher degree.

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Atomic clocks have the benefit that atoms are universal, which means that the oscillation frequency is universal.

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Accuracy of atomic clocks has improved continuously since the first prototype in the 1950s.

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The first generation of atomic clocks were based on measuring caesium, rubidium, and hydrogen atoms.

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The Atomic clocks were the first to use a caesium fountain, which was introduced by Jerrod Zacharias, and laser cooling of atoms, which was demonstrated by Dave Wineland and his colleagues in 1978.

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The goal is to redefine the second when Atomic clocks become so accurate that they will not lose or gain more than a second in the age of the universe.

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The evaluation reports of individual Atomic clocks are published online by the International Bureau of Weights and Measures .

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Twenty-first century experimental atomic clocks that provide non-caesium-based secondary representations of the second are becoming so precise that they are likely to be used as extremely sensitive detectors for other things besides measuring frequency and time.

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The frequency of atomic clocks is altered slightly by gravity, magnetic fields, electrical fields, force, motion, temperature and other phenomena.

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The experimental Atomic clocks tend to continue to improve, and leadership in performance has shifted back and forth between various types of experimental Atomic clocks.

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Accuracy of experimental quantum Atomic clocks has since been superseded by experimental optical lattice Atomic clocks based on strontium-87 and ytterbium-171.

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One theoretical possibility for improving the performance of atomic clocks is to use a nuclear energy transition rather than the atomic electron transitions which current atomic clocks measure.

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In 2013 optical lattice Atomic clocks were shown to be as good as or better than caesium fountain Atomic clocks.

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In 2020 optical Atomic clocks were researched for space applications like future generations of global navigation satellite systems as replacements for microwave based Atomic clocks.

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In February 2022, scientists at the University of Wisconsin-Madison reported a “multiplexed” optical atomic clock, where individual clocks deviated from each other with an accuracy equivalent to losing a second in 300 billion years.

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Optical Atomic clocks are based on forbidden optical transitions in ions or atoms.

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Development of atomic clocks has led to many scientific and technological advances such as precise global and regional navigation satellite systems, and applications in the Internet, which depend critically on frequency and time standards.

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Atomic clocks are installed at sites of time signal radio transmitters.

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Atomic clocks are used in many scientific disciplines, such as for long-baseline interferometry in radio astronomy.

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Galileo System Time is a continuous time scale which is generated on the ground at the Galileo Control Centre in Fucino, Italy, by the Precise Timing Facility, based on averages of different atomic clocks and maintained by the Galileo Central Segment and synchronised with TAI with a nominal offset below 50 nanoseconds.

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Atomic clocks are effective at testing general relativity on smaller and smaller scales.

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Atomic clocks can be used to see how time is influenced by general relativity and quantum mechanics at the same time.

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Atomic clocks keep accurate records of transactions between buyers and sellers to the millisecond or better, particularly in high-frequency trading.

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