Abstract

We exploit a class of path-entangled photon Fock states for robust quantum sensors in the presence of loss. We use a loss model based on beamsplitters and derive a reduced density matrix formalism from which we examine how photon loss affects coherence. It is shown that particular entangled number states, which contain a special superposition of photons in both arms of a Mach-Zehnder interferometer, are resilient to environmental decoherence. We demonstrate an order of magnitude greater visibility with loss, than possible with N00N states.

© 2008 Optical Society of America