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arXiv:1207.6366 · Physical Review A

Experimental determination of the degree of polarization of quantum states

Christian Kothe, Lars S. Madsen, Ulrik L. Andersen, Gunnar G. Bjork

Published Apr 15, 2013• 11 citations
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Abstract

We demonstrate experimental excitation-manifold-resolved polarization characterization of quantum states of light ranging from the few-photon to the many-photon level. In contrast to the traditional characterization of polarization that is based on the Stokes parameters, we experimentally determine the Stokes vector of each excitation manifold separately. Only for states with a given photon number do the methods coincide. For states with an indeterminate photon number, for example Gaussian states, the employed method gives a richer and more accurate description. We apply the method both in theory and in experiment to some common states to demonstrate its advantages.

DOI
10.1103/physreva.87.043814

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We investigate polarization squeezing in squeezed coherent states with varying coherent amplitudes. In contrast to the traditional characterization based on the full Stokes parameters, we experimentally determine the Stokes vector of each excitation subspace separately. Only for states with a fixed photon number do the methods coincide; when the photon number is indefinite, we parse the state in Fock layers, finding that substantially higher squeezing can be observed in some of the single layers. By capitalizing on the properties of the Husimi QQQ function, we map this notion onto the Poincar\'e space, providing a full account of the measured squeezing.