The best atomic clocks are based on ensembles of independent atoms. For these systems, clock precision cannot be better than the standard quantum limit, which scales as N½ (where N is the number of atoms) .
However, a certain class of entangled states known as “squeezed states” are known to have precision better than the standard quantum limit [2,3]. Operating a clock with these states is bound by the ultimate limit to measurement precision, namely the Heisenburg limit. The Heisenburg limit is enhanced over the standard quantum limit by a factor of N½, meaning that this limit scales as N. This can result in clock precision that is orders of magnitude better than traditional clocks.
We are exploring a novel scheme for squeezing atoms using Rydberg states . Starting with an ultracold gas of strontium trapped in an optical lattice potential, the excited state of the strontium clock transition is dressed by a laser that couples to a Rydberg level. The Rydberg interaction creates state-dependent correlations, which squeezes the atoms. Using this squeezed state, the improvement in clock precision can be demonstrated by performing spectroscopy of the clock transition with an ultrastable laser.
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