A new record in atomic clock performance

<p>The pursuit of better atomic clocks has advanced many fields of research, providing better\&nbsp;<span style="line-height: 1.6em;">quantum state control, new insights in quantum science, tighter limits on fundamental constant\&nbsp;</span><span style="line-height: 1.6em;">variation, and improved tests of relativity. This thesis describes the construction and characterization\&nbsp;</span><span style="line-height: 1.6em;">of an </span><sup style="line-height: 1.6em;">87</sup><span style="line-height: 1.6em;">Sr optical lattice clock with a state-of-the-art stable laser. The performance of an atomic\&nbsp;</span><span style="line-height: 1.6em;">clock is typically gauged by two figures of merit: stability and total systematic uncertainty. Stability\&nbsp;</span><span style="line-height: 1.6em;">is the statistical precision of a clock or frequency standard, and the total systematic uncertainty\&nbsp;</span><span style="line-height: 1.6em;">is the combined uncertainty of all known systematic measurement biases. Several demonstrations\&nbsp;</span><span style="line-height: 1.6em;">of clock stability are presented in this work, one of which was the first to significantly outperform\&nbsp;</span><span style="line-height: 1.6em;">ion clocks. The most recent of these measurements resulted in fractional stability of 2.2 x 10</span><sup style="line-height: 1.6em;">-16</sup><span style="line-height: 1.6em;"> at\&nbsp;</span><span style="line-height: 1.6em;">1 s, which is the best reported to date. These stability improvements are used for two systematic\&nbsp;</span><span style="line-height: 1.6em;">evaluations of our clock. The first full evaluation at 6.4 x 10<sup>-18</sup> total uncertainty took the record\&nbsp;</span><span style="line-height: 1.6em;">for best clock performance. The second evaluation used improved strategies for systematic measurements,\&nbsp;</span><span style="line-height: 1.6em;">achieving a new best total systematic uncertainty of 2.1 x 10<sup>-18</sup>. With a combination\&nbsp;</span><span style="line-height: 1.6em;">of accurate radiation thermometry and temperature stabilization of the measurement environment,\&nbsp;</span><span style="line-height: 1.6em;">we demonstrate the first lattice clock to achieve the longstanding goal of 10<sup>-18</sup> level uncertainty\&nbsp;</span><span style="line-height: 1.6em;">in the formidable blackbody radiation shift. Improvements in the density, lattice ac Stark, and\&nbsp;</span><span style="line-height: 1.6em;">dc Stark shifts were also a result of innovations that are described in this thesis. Due to the low\&nbsp;</span><span style="line-height: 1.6em;">total uncertainty of the Sr clock, timekeeping based on this system would not lose a second in 15\&nbsp;</span><span style="line-height: 1.6em;">billion years (longer than the age of the Universe), and it is sensitive to a gravitational redshift\&nbsp;</span><span style="line-height: 1.6em;">corresponding to a height change of 2 cm above the Earth\textquoterights surface.</span></p>
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University of Colorado Boulder
Boulder, CO
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