Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Reconstructing the density matrix of a spin s through Stern-Gerlach
  measurements (II)   The density matrix of a spin s is fixed uniquely if the probabilities to
obtain the value s upon measuring n.S are known for 4s(s+1) appropriately
chosen directions n in space. These numbers are just the expectation values of
the density operator in coherent spin states, and they can be determined in an
experiment carried out with a Stern-Gerlach apparatus. Furthermore, the
experimental data can be inverted providing thus a parametrization of the
statistical operator by 4s(s+1) positive parameters.

4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
2
The categories of this paper are: math
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat