Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of complete and continuous Wigner functions for discrete
  atomic systems   We measure complete and continuous Wigner functions of a two-level cesium
atom in both a nearly pure state and highly mixed states. We apply the method
[T. Tilma et al., Phys. Rev. Lett. 117, 180401 (2016)] of strictly constructing
continuous Wigner functions for qubit or spin systems. We find that the Wigner
function of all pure states of a qubit has negative regions and the negativity
completely vanishes when the purity of an arbitrary mixed state is less than
$\frac{2}{3}$. We experimentally demonstrate these findings using a single
cesium atom confined in an optical dipole trap, which undergoes a nearly pure
dephasing process. Our method can be applied straightforwardly to multi-atom
systems for measuring the Wigner function of their collective spin state.

19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn