Berlin 2014 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 41: Precision measurements and metrology I

Q 41.6: Vortrag

Donnerstag, 20. März 2014, 15:30–15:45, DO24 1.101

Precision measurements with Gaussian and non-Gaussian states — •Daniel Braun^1,2, Claude Fabre³, Pu Jian³, Olivier Pinel⁴, and Nicolas Treps³ — ¹Laboratoire de Physique Théorique, Universit *e Paul Sabatier and CNRS, 31062 Toulouse, France — ²Institut für theoretische Physik, Universität Tübingen, 72076 Tübingen, Germany — ³Laboratoire Kastler Brossel, Université Pierre et Marie Curie-Paris 6, ENS, CNRS, 75252 Paris, France — ⁴Centre for Quantum Computation and Communication Technology, Department of Quantum Science, The Australian National University, Canberra, ACT 0200, Australia

We calculate the quantum Cramér-Rao bound for the sensitivity with which parameters encoded in general single-mode (possibly mixed) Gaussian states, or non-Gaussian states obtained by photon-addition or -subtraction can be measured. We apply the formula for the Gaussian state to the problems of estimating phase, purity, loss, amplitude, and squeezing and provide the full quantum Fisher information (QFI) matrix for simultaneous measurement of several parameters. Our results unify previously known partial results and constitute a complete solution of the problem. For the photon-subtracted state, we show that the QFI diverges in the limit of no squeezing and almost no photons, which enable in principle arbitrarily precise measurements with essentially no light. However, this divergence is cancelled by the decaying success probability of the preparation scheme. In the limit of large photon numbers N, the non-classicality of the light only leads to a relative correction of order 1/N.