Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Strongly polarizing weakly coupled $^{13}$C nuclear spins with optically
  pumped nitrogen-vacancy center   Enhancing the polarization of nuclear spins surrounding the nitrogen-vacancy
(NV) center in diamond has attracted widespread attention recently due to its
various applications. Here we present an analytical theory and comprehensive
understanding on how to optimize the dynamic nuclear polarization by an
optically pumped NV center near the ground state level anticrossing. Our
results not only provide a parameter-free explanation and a clearly physics
picture for the recently observed polarization dependence on the magnetic field
for strongly coupled $^{13}$C nuclei [H. J. Wang \textit{et al}., Nat. Commun.
4, 1 (2013)], but also demonstrate the possibility to strongly polarize weakly
coupled $^{13}$C nuclei under weak optical pumping and suitably chosen magnetic
field. This allows sensitive magnetic control of the $^{13}$C nuclear spin
polarization for NMR applications and significant suppression of the $^{13}$C
nuclear spin noise to prolong the NV spin coherence time.

15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
19
The categories of this paper are: eess
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph