Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Direct measurement of the Wigner function by photon counting   We report a direct measurement of the Wigner function characterizing the
quantum state of a light mode. The experimental scheme is based on the
representation of the Wigner function as an expectation value of a displaced
photon number parity operator. This allowed us to scan the phase space
point-by-point, and obtain the complete Wigner function without using any
numerical reconstruction algorithms.

27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
12
The categories of this paper are: nucl-th
5
The categories of this paper are: gr-qc