Entanglement and phase properties of noisy NOON states
Martin Bohmann, Jan Sperling, W. Vogel · Physical Review A · 2015
Quantum metrology and quantum information necessitate a profound study of suitable states. Attenuations induced by free-space communication links or fluctuations in the generation of such states limit the quantum enhancement in possible applications. For this reason we investigate quantum features of mixtures of so-called NOON states propagating in atmospheric channels. First, we show that noisy NOON states can still yield a phase resolution beyond classical limitations. Second, we identify entanglement of noisy NOON states after propagation in fluctuating loss channels. To do so, we apply the partial transposition criterion. Our theoretical analysis formulates explicit bounds which are indispensable for experimental verification of quantum entanglement and applications in quantum metrology.