Experiments with numerically controlled atomic clocks

摘要

Long term timing stability of present atomic clocks can be considerably improved by simple numerical algorithms which correct both the inherent frequency bias and the effects of supply voltage variations and outside temperature. Rubidium units are demonstrated to operate with less than 100 ns errors per week or any sensible longer interval corresponding to relative uncertainties of 10/sup -13/. Often a linear subtraction of frequency offset which can be realized by a microprocessor controlled digital delay line is sufficient. A cesium clock could be run at 10/sup -15/ level, but reliable and reasonable real-time measurement techniques do not yet exist.