Conference Paper

Frequency Measurement of an Optical Lattice Clock

Nat. Inst. of Adv. Ind. Sci. & Technol, Ibaraki;
DOI: 10.1109/LEOSST.2007.4288378 Conference: IEEE/LEOS Summer Topical Meetings, 2007 Digest of the
Source: IEEE Xplore

ABSTRACT A frequency measurement system is developed away from a National Metrological Institute with a frequency link to International Atomic Time (TAI). The absolute frequency of the 1S0 -3P0 clock transition of the 87Sr lattice clock is determined to be 429,228,004,229,875(4) Hz. The frequency measurement system is being further improved by introducing an optical fiber link and by upgrading the GPS link.

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    ABSTRACT: An ultrastable optical clock based on neutral atoms trapped in an optical lattice is proposed. Complete control over the light shift is achieved by employing the 5s(2) 1S0-->5s5p 3P0 transition of 87Sr atoms as a "clock transition." Calculations of ac multipole polarizabilities and dipole hyperpolarizabilities for the clock transition indicate that the contribution of the higher-order light shifts can be reduced to less than 1 mHz, allowing for a projected accuracy of better than 10(-17).
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    ABSTRACT: The comparison of different atomic transition frequencies over time can be used to determine the present value of the temporal derivative of the fine structure constant alpha in a model-independent way without assumptions on constancy or variability of other parameters, allowing tests of the consequences of unification theories. We have measured an optical transition frequency at 688 THz in 171Yb+ with a cesium atomic clock at 2 times separated by 2.8 yr and find a value for the fractional variation of the frequency ratio f(Yb)/f(Cs) of (-1.2+/-4.4)x10(-15) yr(-1), consistent with zero. Combined with recently published values for the constancy of other transition frequencies this measurement sets an upper limit on the present variability of alpha at the level of 2.0x10(-15) yr(-1) (1sigma), corresponding so far to the most stringent limit from laboratory experiments.
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    ABSTRACT: We report the observation of a higher-order frequency shift due to the trapping field in a (87)Sr optical lattice clock. We show that, at the magic wavelength of the lattice, where the first-order term cancels, the higher-order shift will not constitute a limitation to the fractional accuracy of the clock at a level of 10(-18). This result is achieved by operating the clock at very high trapping intensity up to 400 kW/cm(2) and by a specific study of the effect of the two two-photon transitions near the magic wavelength.
    Physical Review Letters 04/2006; 96(10):103003. · 7.73 Impact Factor