Efficient Atomic Clocks Operated with Several Atomic Ensembles

Atomic clocks are typically operated by locking a local oscillator (LO) to a single atomic ensemble. In this Letter, we propose a scheme where the LO is locked to several atomic ensembles instead of one. This results in an exponential improvement compared to the conventional method and provides a stability of the clock scaling as (alpha N)(-m/2) with N being the number of atoms in each of the m ensembles and alpha a constant depending on the protocol being used to lock the LO.