Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Complementary reductions for two qubits   In connection with optimal state determination for two qubits, the question
was raised about the maximum number of pairwise complementary reductions. The
main result of the paper tells that the maximum number is 4, that is, if A1,
A2,... Ak are pairwise complementary (or quasi-orthogonal) subalgebras of the
algebra of all 4x4$ matrices and they are isomorphic to the algebra of all 2x2
matrices, then k is at most 4. In the way to this result, contributions are
made to the understanding of the structure of complementary reductions.

6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th