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 Cram{\'e}r-Rao bound for such a setup. The answer is squeezed vacuum.
@article{arxiv.1306.2677,
title = {Optimal quantum-enhanced interferometry using a laser power source},
author = {Matthias D. Lang and Carlton M. Caves},
journal= {arXiv preprint arXiv:1306.2677},
year = {2013}
}
Comments
8 pages, 1 figure, replaced version with minor corrections