Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Complementarity in single photon interference - the role of mode
  functions and vacuum fields   Single photon first order interferences of spatially separated regions from
the cone structure of spontaneous parametric down conversion allow for
analyzing the role of the mode function in quantum optics. In earlier
experiments the role of the vacuum fields could be demonstrated in induced
coherence experiments as the source of complementarity \cite{Heu14}. Here the
spatial coherence properties of these vacuum fields are measured and as the
physical reason for complementarity in single photon quantum optics
demonstrated.

27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con