  We study the precise phase estimation using squeezed states with photon
losses present. Our exact quantum Fisher information calculation shows
significant quantum enhancement and thus reveals the benchmark for practical
quantum metrology in this noisy scenario. However, we find that the existing
parity measurement scheme [P.M. Anisimov et al, Phys. Rev. Lett. 104, 103602
(2010)] behaves worse than even classical cases given very small losses, unless
we take an appropriate loss dependent phase shift. Using our formulae, the two
optimized aspects including the pre-detection phase shift and the consequent
light intensity of a tradeoff strategy for photon resource arrangement can be
both calculated. Therefore our result makes it possible to experimentally
realize quantum metrology of phase estimation with squeezed states.
