Date of Award
Doctor of Philosophy (PhD)
The advancement of optical atomic clocks in the past two decades has motivated many potential applications in navigation, communication, and science. Accurate optical clocks that outperform the current cesium time standard also trigger a discussion about a possible redefinition of the SI second. The 27Al+ quantum logic clocks developed at the National Institute of Standards and Technology (NIST) were the first to achieve the clock fractional frequency uncertainty below 10-17 in 2010. To date, a few research groups around the world have demonstrated optical clocks based on various atomic transitions with fractional frequency uncertainty in the 10-18 range. The accuracy of the previous 27Al+ clocks was limited by the second order Doppler (time dilation) shift and the blackbody shift. Since 2010, the third 27Al+ optical clock is being developed at NIST to achieve a higher accuracy. The frequency uncertainties dominant in the previous clocks are controlled and reduced in the current optical clock. The new design of the ion trap system has reduced significantly both the blackbody radiation shift uncertainty and the time dilation shift uncertainty due to micromotion, while the time dilation shift uncertainty due to the secular motion has been reduced by more than an order of magnitude by operating the optical clock near the three dimensional zero-point energy. Despite those previously dominant uncertainties, several other systematic effects are being evaluated and some other efforts are being made to achieve a total uncertainty towards 1.0 x 10-18. In this thesis, I will document the detail of the construction and evaluation of the current 27Al+ optical clock developed at NIST.
Chen, Jwo-Sy, "Ticking near the Zero-Point Energy: Towards 1 x 10^-18 Accuracy in Al^+ Optical Clocks" (2017). Physics Graduate Theses & Dissertations. 218.