Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin Environment Engineering for a Persistent Current Qubit   A persistent current qubit has two quantum states with opposite currents
flowing in a superconducting loop. Their magnetic field couple to nuclear
spins. The qubit state is not only perturbed by the spins but it also gets
entangled with the spins' state on a very short timescale. However, when the
same spins are exposed to a strong but less than critical external magnetic
field, then the qubit field is just a small perturbation on top of the external
field and the entanglement with each spin is negligible. For a qubit which is
more microscopic than certain threshold this partial entanglement results in
negligible partial decoherence.

17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ