Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Single-photon nonreciprocal excitation transfer with non-Markovian
  retarded effects   We study at the single-photon level the nonreciprocal excitation transfer
between emitters coupled with a common waveguide. Non-Markovian retarded
effects are taken into account due to the large separation distance between
different emitter-waveguide coupling ports. It is shown that the excitation
transfer between the emitters of a small-atom dimer can be obviously
nonreciprocal by introducing between them a coherent coupling channel with
nontrivial coupling phase. We prove that for dimer models the nonreciprocity
cannot coexist with the decoherence-free giant-atom structure although the
latter markedly lengthens the lifetime of the emitters. In view of this, we
further propose a giant-atom trimer which supports both nonreciprocal transfer
(directional circulation) of the excitation and greatly lengthened lifetime.
Such a trimer model also exhibits incommensurate emitter-waveguide entanglement
for different initial states in which case the excitation transfer is however
reciprocal. We believe that the proposals in this paper are of potential
applications in large-scale quantum networks and quantum information
processing.

9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
27
The categories of this paper are: comp-gas