Realistic constraints on photonic quantum interferometry - art. no. 69060H

We analyze the phase estimation ability of photonic N00N states propagating in a lossy medium. In such a medium a N00N state of N enangled photons cannot achieve the maximum 1/N phase estimation resolution. In fact, unless the transmittance of the medium is extremely high, a signal comprised of an attenuated separable state of N photons will produce a better phase estimate than a comparable signal of an equally attenuated N00N state. Thus, for most practical applications the resolution provided photonic N00N states is actually worse than the 1/root N Standard Quantum Limit. This performance deficit becomes more pronounced as the number of photons in the signal increases.