title: Sr lattice clock at 1 x 10(-16) fractional uncertainty by remote optical evaluation with a Ca clock.
abstract: Optical atomic clocks promise timekeeping at the highest precision and accuracy, owing to their high operating frequencies. Rigorous evaluations of these clocks require direct comparisons between them. We have realized a high-performance remote comparison of optical clocks over kilometer-scale urban distances, a key step for development, dissemination, and application of these optical standards. Through this remote comparison and a proper design of lattice-confined neutral atoms for clock operation, we evaluate the uncertainty of a strontium (Sr) optical lattice clock at the 1 x 10(-16) fractional level, surpassing the current best evaluations of cesium (Cs) primary standards. We also report on the observation of density-dependent effects in the spin-polarized fermionic sample and discuss the current limiting effect of blackbody radiation-induced frequency shifts.
authors.affiliation: JILA, National Institute of Standards and Technology, and University of Colorado, Department of Physics, University of Colorado, Boulder, CO 80309-0440, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Ludlow
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authors.initials: T
authors.lastname: Zelevinsky
authors.forename: G K
authors.initials: GK
authors.lastname: Campbell
authors.forename: S
authors.initials: S
authors.lastname: Blatt
authors.forename: M M
authors.initials: MM
authors.lastname: Boyd
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authors.lastname: de Miranda
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authors.initials: MJ
authors.lastname: Martin
authors.forename: J W
authors.initials: JW
authors.lastname: Thomsen
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authors.lastname: Foreman
authors.forename: Jun
authors.initials: J
authors.lastname: Ye
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authors.lastname: Fortier
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authors.lastname: Stalnaker
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authors.initials: SA
authors.lastname: Diddams
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authors.lastname: Le Coq
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authors.lastname: Barber
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authors.lastname: Poli
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authors.lastname: Lemke
authors.forename: K M
authors.initials: KM
authors.lastname: Beck
authors.forename: C W
authors.initials: CW
authors.lastname: Oates