  We propose a realization of the two-impurity Anderson model in a double
quantum-dot device. When charge transfer between the dots is suppressed the
system exhibits a quantum phase transition, controlled by a surface of
non-Fermi liquid fixed points parameterized by the charge valences of the dots.
Employing conformal field theory techniques, we identify the scaling exponents
that govern transport and thermodynamics close to criticality. We also
determine the dynamical exponents that set the time scale for buildup of the
non-Fermi liquid state after the system is suddenly shifted into the critical
region, e.g. by a change of a nearby gate voltage.
