Making the world´s best atomic clock

I will report our recent effort towards realizing the full potential of a many-particle clock with a state-of-the-art stable laser. We have achieved fractional stability of 2.2 × 10^-16 at 1 s for the JILA Sr optical atomic clock. We have also reduced the total uncertainty of our clock to 2.1 × 10^-18 in fractional frequency units. Both represent new records for the performance of an atomic clock.