  We report on devices based on graphene charge detectors (CDs) capacitively
coupled to graphene and carbon nanotube quantum dots (QDs). We focus on back
action effects of the CD on the probed QD. A strong influence of the bias
voltage applied to the CD on the current through the QD is observed. Depending
on the charge state of the QD the current through the QD can either strongly
increase or completely reverse as a response to the applied voltage on the CD.
To describe the observed behavior we employ two simple models based on single
electron transport in QDs with asymmetrically broadened energy distributions of
the source and the drain leads. The models successfully explain the back action
effects. The extracted distribution broadening shows a linear dependency on the
bias voltage applied to the CD. We discuss possible mechanisms mediating the
energy transfer between the CD and QD and give an explanation for the origin of
the observed asymmetry.
