Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Advances in Optical and Microwave Nonreciprocity   Modern photonic and quantum technologies demand reciprocity breaking, e.g.,
isolators, full-duplex systems, noise isolation in quantum computers,
motivating searching for practical approaches beyond magnet-based devices. This
work overviews the up-and-coming advances in optical nonreciprocity, including
new materials (Weyl semimetals, topological insulators, metasurfaces), active
structures, time-modulation, PT-symmetry breaking, nonlinearity, quantum
nonlinearity, unidirectional gain and loss, chiral quantum states, and valley
polarization.

32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con