  Double quantum dots can provide an experimental realization of the 2 impurity
Kondo model which exhibits a non-Fermi liquid quantum critical point (QCP) at a
special value of its parameters. We generalize our recent study of double
quantum dots in series \cite{Sela08} to a parallel configuration with an
Aharonov-Bohm flux. We present an exact universal result for the finite
temperature and finite voltage conductance $G[V,T]$ along the crossover from
the QCP to the low energy Fermi liquid phase. Compared to the series
configuration, here generically $G[V,T] \ne G[-V,T]$, leading to current
rectification.
