Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Controllable coupling of superconducting flux qubits   We have realized controllable coupling between two three-junction flux qubits
by inserting an additional coupler loop between them, containing three
Josephson junctions. Two of these are shared with the qubit loops, providing
strong qubit--coupler interaction. The third junction gives the coupler a
nontrivial current--flux relation; its derivative (i.e., the susceptibility)
determines the coupling strength J, which thus is tunable in situ via the
coupler's flux bias. In the qubit regime, J was varied from ~45
(antiferromagnetic) to ~ -55 mK (ferromagnetic); in particular, J vanishes for
an intermediate coupler bias. Measurements on a second sample illuminate the
relation between two-qubit tunable coupling and three-qubit behavior.

30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph