High-accuracy measurement of the differential scalar polarizability of a 88Sr+ clock using the time-dilation effect.

We report a high-accuracy measurement of the differential static scalar polarizability Δα(0) of the 5s(2)S(1/2)-4d(2)D(5/2) transition of the (88)Sr(+) ion. The high accuracy is obtained by comparing the micromotion-induced positive scalar Stark shift to the negative time-dilation shift. Measurement of the trap drive frequency where these shifts cancel is used to determine Δα(0) without the need to determine the electric field.

88Sr+ 445-THz single-ion reference at the 10(-17) level via control and cancellation of systematic uncertainties and its measurement against the SI second.

We describe experiments and measurements on a trapped and laser-cooled single ion of (88)Sr(+) which, when probed on its reference 5s (2)S(1/2)→4d (2)D(5/2) transition at 445 THz, provides an optical frequency standard of evaluated accuracy outperforming the current realization of the SI second. Studies are presented showing that micromotion-associated shifts of the standard can be reduced to the 10(-18) level and uncertainties in the blackbody-induced shifts for the current system are at the low 10(-17) level due to the relatively well-known polarizability of the strontium ion system and careful choice of the trap structure. The current evaluated systematic shifts for the ion transition are at a fractional uncertainty of 2×10(-17).