Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Preparation of pure and mixed polarization qubits and the direct
  measurement of figures of merit   Non-classical joint measurements can hugely improve the efficiency with which
certain figures of merit of quantum systems are measured. We use such a
measurement to determine a particular figure of merit, the purity, for a
polarization qubit. In the process we highlight some of subtleties involved in
common methods for generating decoherence in quantum optics.

35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat