Single electron switching in a parallel quantum dot

Low-temperature conductance measurements have been performed upon a parallel quantum-dot configuration defined in the two-dimensional electron gas of a GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As heterostructure. The observed Coulomb-blockade oscillations of the conducting dot exhibit pronounced periodic shifts as a consequence of the tunable coupling to the nonconducting dot. We show that the transport is essentially determined by the interdot capacitance and that the addition of a single electron to the nonconducting dot can switch the device conductance from a maximum to a Coulomb-blockade minimum.