Radio frequency charge sensing in a Si double quantum dot device*

Coherent spin manipulation has recently been demonstrated in a variety of silicon based devices.\footnote{B. M. Maune \emph{et al.}, Nature \textbf{481}, 344 (2012).}$^,$\footnote{J. J. Pla \emph{et al.}, Nature \textbf{489}, 541 (2012).} We fabricate accumulation mode double quantum dot devices and use radio frequency reflectometry to perform fast charge sensing in the few-electron regime. Our devices employ a nearby single quantum dot as a charge sensor. Charge transitions in the double dot result in a $\sim$60\% relative change in the charge sensor conductance when the sensor is operated in the Coulomb blockade regime, compared to a $\sim$1\% conductance change when the sensor is operated as a traditional quantum point contact. Further development of these techniques may enable us to perform single shot spin readout in a silicon quantum dot.