Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pairing of Cooper pairs in a Josephson junction network containing an
  impurity   We show how to induce pairing of Cooper pairs (and, thus, $4e$
superconductivity) as a result of local embedding of a quantum impurity in a
Josephson network fabricable with conventional junctions. We find that a
boundary double Sine-Gordon model provides an accurate description of the dc
Josephson current patterns, as well as of the stable phases accessible to the
network. We point out that tunneling of pairs of Cooper pairs is robust against
quantum fluctuations, as a consequence of the time reversal invariance, arising
when the central region of the network is pierced by a dimensionless magnetic
flux $\phi = \pi$. We find that, for $\phi = \pi$, a stable attractive finite
coupling fixed point emerges and point out its relevance for engineering a two
level quantum system with enhanced coherence.

8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th