Least count of cesium clock and maximum possible significant figures for time We know that a second is defined as being equal to the time duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the fundamental unperturbed ground-state of the caesium-133 atom(form wikipedia).Hence least count of this clock will be $\frac{1}{9192 631770}$ seconds
From my understanding of least count and significant figures I conclude that it is not possible to measure time duration less than $\frac{1}{9192 631770}$ seconds accurately. Is my conclusion correct?
Is there any workaround for this?
 A: Your conclusion is not correct. Current atomic clocks based on optical transitions are much more accurate and precise than that. So time durations less than 1/9192631770 s can indeed be accurately measured.
The kernel of truth to your conclusion is that such time durations cannot be accurately known in SI units. However, SI units have no particular existential prominence. Just because we cannot accurately measure such durations in SI seconds does not mean we cannot measure them at all.
As a side note, we can detect phase differences less than $2\pi$, so the limit would not be 1/9192631770 s anyway. What is important is not the frequency, but how well that frequency stays in phase so that you can detect differences. Right now that is on the order of $10^{-16}$ for Cesium clocks.
A: The number $N=9\, 192\, 631\, 770$ is used to define a second. Do not mistake this as an accuracy or precision. These are completely different concepts from the definition. Thus it is of course possible to measure things with an accuracy lower than $1/N$.
