Talk by Claude Fabre, Universite Pierre et Marie Curie – Niels Bohr Institute - University of Copenhagen

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Talk by Claude Fabre, Universite Pierre et Marie Curie

Multimode Gaussian quantum light, which includes multimode squeezed and multipartite quadrature entangled light, is a very general and powerful quantum resource which has already successfully used in quantum information processing and metrology involving continuous variables.

It is possible using information theory techniques to determine the ultimate sensitivity in the estimation of any parameter when the information about this parameter is encoded in multimode Gaussian light, irrespective of the exact information extraction protocol used in the estimation.

I will show that, for a given set of available quantum resources, the most economical way to maximize the sensitivity is to put the most squeezed state available in a well defined light mode. This implies that it is not possible to take advantage of the existence of squeezed fluctuations in other modes, nor of quantum correlations and entanglement between different modes.

I will finally show that it is actually possible to reach this bound by an apropriate homodyne detection scheme, and give some examples of applications.