SOME LIMITS TO PRECISION PHASE MEASUREMENT

States near the vacuum having (($) over cap n) much less than 1 are us ed for the precision determination of a phase shift. When this phase s hift 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 n umber of quanta N-tot. We study in detail some examples of these near- vacuum schemes and show that in the absence of loss or noise their sen sitivity approaches that of squeezed-state interferometry.