Practical quantum interferometry using photonic N00N states

Abstract

We study the phase estimation abilites of photonic N 00 N states, propagating in an attenuating medium, is analyzed. It is shown that N 00 N states of a given number of enangled photons N , never achieve the 1/ N Heisenberg limit if the propagation occurs through lossy medium. It is also shown that a signal comprised of an attenuated separable state of N photons will actually produce a better phase estimate than a signal comprised of an equally attenuated N 00 N state unless the transmittance of the medium is very high. Thus, for most practical applications in realistic scenarios with attenuation, the resolution of N 00 N state-based phase estimation not only does not achieve the Heisenberg Limit, but is actually worse than the 1/(square root of)N Standard Quantum Limit. This performance deficit becomes more pronounced as the number, N , of photons in the signal increases.