Reconstructing the density matrix of a spinsthrough Stern-Gerlach measurements: II

Abstract
The density matrix of a spin s is fixed uniquely if the probabilites to obtain the value s upon measuring . are known for 4s(s+1) appropriately chosen directions in space. These numbers are just the expectation values of the density operator in coherent spin states, and they are easily obtained in an experiment carried out with a Stern-Gerlach apparatus. Furthermore, the experimental data is non-redundant, and it can be inverted explicitly which allows for a parametrization of the statistical operator by the 4s(s+1) positive parameters.
All Related Versions