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Quantum Physics, quant-ph, Astrophysics, Instrumentation and Methods for Astrophysics, astro-ph.IM
Abstract:
The fundamental quantum interferometry bound limits the sensitivity of an
interferometer for a given total rate of photons and for a given decoherence
rate inside the measurement device.We theoretically show that the recently
reported quantum-noise limited sensitivity of the squeezed-light-enhanced
gravitational-wave detector GEO600 is exceedingly close to this bound, given
the present amount of optical loss. Furthermore, our result proves that the
employed combination of a bright coherent state and a squeezed vacuum state is
generally the optimum practical approach for phase estimation with high
precision on absolute scales. Based on our analysis we conclude that neither
the application of Fock states nor N00N states or any other sophisticated
nonclassical quantum states would have yielded an appreciably higher
quantum-noise limited sensitivity.