Performance of a portable rubidium cold-atom optical clock*

There is mounting interest in portable optical atomic clocks for enhancing or replacing GPS timing signals in both commercial and defense-related applications. Optical clocks based on warm vapors are simple in implementation yet performance at long time scales is limited by systematic thermal sensitivities of the system. Vescent, in collaboration with ColdQuanta, has designed and built a portable optical clock based on trapped rubidium atoms to 1) utilize the reduced complexity of rubidium-based systems compared to higher performance cold-atom optical clocks and 2) improve on the long-term performance compared to optical clocks based on hot vapor systems. Current Allan Deviation performance is measured to be 5×10^-12/√τ and is shot-noise limited by the fluorescence detection. Improvements to the systems are on-going, and the size, weight, electrical power, performance, and limitations of the system will be discussed in detail.