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(a) Electron micrograph of the twin rf-SET and double-dot device. The rf-SETs detect the charge state of the two metal dots which are coupled by a tunnel junction (center of image); (b) is a schematic showing the two rf-SETs and the double-dot with associated gates and capacitances.
(a) Time-domain response to both rf-SETs to a square wave signal applied to gate A2 via a attenuator . All measurements taken at ; (b) (taken from Ref. 12), the frequency-domain response to both rf-SETs to a AM signal (blue trace). We measure sensitivities of for SET1 and for SET2. Inset: Charge sensitivity as a function of frequency. Below the sensitivity is limited by noise.
(a) Time-domain data for , obtained by averaging 256 times. (b) single-shot response of SET2 to a and step in a measurement time of . (c)–(e) show the corresponding probability distribution functions for each signal. We measure a time-domain sensitivity of in a bandwidth of for SET2.
(a) The simultaneous response of both SETs to electron transfer between the two metal dots. -axis is voltage from demodulation circuit, proportional to reflected rf power; (b) sharp peaks are produced in the correlation whenever a transfer event occurs; (c) shows the bias applied to gates A1 and A2 to create a differential electric field; (d) single-shot time-domain measurements of charge transfer in the double dot system; (e) correlation of the signals from both SETs allows for error rejection in the event of charge noise (shaded region). All data data taken at .
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