Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Faithful entanglement purification for high-capacity quantum
  communication with two-photon four-qubit systems   As the hyperentanglement of photon systems presents lots of unique
opportunities in high-capacity quantum networking, the hyperentanglement
purification protocol (hyper-EPP) becomes a vital project work and the quality
of its accomplishment attracts much attention recently. Here we present the
first theoretical scheme of faithful hyper-EPP for nonlocal two-photon systems
in two degrees of freedom (DOFs) by constructing several fidelity-robust
quantum circuits for hyper-encoded photons. With this faithful hyper-EPP, the
bit-flip errors in both the polarization and spatial-mode DOFs can be
efficiently corrected and the maximal hyperentanglement in two DOFs could be in
principle achieved by performing the hyper-EPP multiple rounds. Moreover, the
fidelity-robust quantum circuits, parity-check quantum nondemolition detectors,
and SWAP gates make this hyper-EPP works faithfully as the errors coming from
practical scattering, in these quantum circuits, are converted into a
detectable failure rather than infidelity. Furthermore, this hyper-EPP can be
directly extended to purify photon systems entangled in single polarization or
spatial-mode DOF and that hyperentangled in polarization and
multiple-spatial-mode DOFs.

23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys