Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hidden Bell correlations in the four-level atom   We extend the Bell inequality known for two qubits to the four-level atom,
including an artificial atom realized by the superconducting circuit, and qudit
with j=3/2. We formulate the extended inequality as the inequality valid for an
arbitrary Hermitian nonnegative 4x4-matrix with unit trace for both separable
and entangled matrices.

31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con