New Scientist – Corey Campbell at the Georgia Institute of Technology in Atlanta and colleagues have devised a scheme that uses lasers to carefully control the spatial orientation of the electron orbits in atoms. A thorium clock controlled in this way would drift by just 1 second in 200 billion years. This is 60 times the accuracy of existing atomic clocks.
This work has shown that the usual sources of clock shifts are suppressed in the proposed system, so that clock operation with inaccuracy approaching 1X10^-19 appears viable. With a more aggressive pursuit of systematic shift compensation and suppression, this value may very well be lowered to the 10^-20 scale, however, other systematic clock shift mechanisms may become operational at this level.