Aspects of practical remote quantum sensing

Abstract

We consider the viability of photonic N00N states for practical remote quantum sensing in realistic atmospheres. This is done by analyzing the phase estimation performance of N-photon N00N states propagating in an attenuating medium. It is shown that the 1/N Heisenberg limit is never achieved. Moreover, an attenuated N00N state will actually produce a worse phase estimate than an equally attenuated N-photon separable state unless the transmittance of the medium is sufficiently high. The transmittance threshold for which the N00N states perform better than separable states increases as the number of signal photons increases. The amount of photon attenuation that arises in realistic, turbulent atmospheres is generally far below this threshold even for low N N00N states. Photonic N00N states are thus not viable for use in practical remote quantum sensing.