  By means of the non-equilibrium Green function and equation of motion method,
the electronic transport is theoretically studied through a parallel-coupled
double quantum dots(DQD) in the presence of the on-dot Coulomb correlation,
with an emphasis put on the quantum interference. It has been found that in the
Coulomb blockage regime, the quantum interference between the bonding and
antiboding DQD states or that between their Coulomb blockade counterparts may
result in the Fano resonance in the conductance spectra, and the Fano peak
doublet may be observed under certain non-equilibrium condition. The
possibility of manipulating the Fano lineshape is predicted by tuning the
dot-lead coupling and magnetic flux threading the ring connecting the dots and
leads. Similar to the case without Coulomb interaction, the direction of the
asymmetric tail of Fano lineshape can be flipped by the external field. Most
importantly, by tuning the magnetic flux, the function of four relevant states
can be interchanged, giving rise to the swap effect, which might play a key
role as a qubit in the quantum computation.
