Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multi-photon interference in the spectral domain by direct heralding of
  superposition states   Multi-photon interference is central to photonic quantum information
processing and quantum simulation, usually requiring multiple sources of
non-classical light followed by a unitary transformation on their modes. Here,
we observe interference in the four-photon events generated by a single silicon
waveguide, where the different modes are six frequency channels. Rather than
requiring a unitary transformation, the frequency correlations of the source
are configured such that photons are generated in superposition states across
multiple channels, and interference effects can be seen without further
manipulation. This suggests joint spectral engineering is a tool for
controlling complex quantum photonic states without the difficulty of
implementing a large unitary interferometer, which could have practical
benefits in various applications of multi-photon interference.

7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
2
The categories of this paper are: math
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
19
The categories of this paper are: eess