Some limits to precision phase measurement
Samuel L. Braunstein · Physical Review A · 1994
States near the vacuum having 〈n^〉\ensuremath{\ll}1 are used for the precision determination of a phase shift. When this phase shift is sampled by enough of these near-vacuum states, its size may be extracted via data analysis. We calculate the achievable sensitivity of such schemes when we are limited in our resources to a mean total number of quanta ${\mathit{N}}_{\mathrm{tot}}$. We study in detail some examples of these near-vacuum schemes and show that in the absence of loss or noise their sensitivity approaches that of squeezed-state interferometry.