This criterion has two factors, the first factor is the spin noise reduction, i.e. how much the quantum noise in formula_48 is reduced relative to the coherent (unentangled) state. The second factor is how much the coherence (the length of the Bloch vector, formula_59) is reduced due to the squeezing procedure. Together these quantities tell you how much metrological enhancement the squeezing procedure gives. Here, metrological enhancement is the reduction in averaging time or atom number needed to make a measurement of a specific uncertainty. 20 dB of metrological enhancement means the same precision measurement can be made with 100 times fewer atoms or 100 times shorter averaging time.