title: Optimal quantum-enhanced interferometry using a laser power source.
abstract: We consider an interferometer powered by laser light (a coherent state) into one input port and ask the following question: what is the best state to inject into the second input port, given a constraint on the mean number of photons this state can carry, in order to optimize the interferometer's phase sensitivity? This question is the practical question for high-sensitivity interferometry. We answer the question by considering the quantum Cramér-Rao bound for such a setup. The answer is squeezed vacuum.
authors.affiliation: Center for Quantum Information and Control, University of New Mexico, Albuquerque, New Mexico 87131-0001, USA.
authors.forename: Matthias D
authors.initials: MD
authors.lastname: Lang
authors.forename: Carlton M
authors.initials: CM
authors.lastname: Caves