Study of Single-Charge Polarization on a Pair of Charge Qubits Integrated Onto a Silicon Double Single-Electron Transistor Readout

This paper reports on integration of two silicon (Si) charge quantum bits (qubits) and series-connected double single-electron transistors (DSETs) as readout for the first time. We design and fabricate the DSETs composed of double quantum dots (DQDs) connected in series with two side gates patterned on a silicon-on-insulator substrate. The individual SETs are sufficiently sensitive to detect single-charge polarization on the adjacent charge qubits. The fabricated DSETs are characterized at a temperature of 4.2 K by changing the gate voltages applied to the two side gates. The measured Coulomb oscillation characteristics exhibit a clearly defined hexagon pattern, manifesting that the patterned DQDs of the DSETs, indeed, act as interacting charging islands. These results agree very well with the results of equivalent circuit simulation combined with 3-D capacitance simulation. Furthermore, we simulate how single-charge configurations on two charge qubits are sensed with the DSETs by using the measured electrical characteristics for the DSET and the equivalent model. Finally, the scaling-up properties of the proposed system to multiple single-electron transistors (MSETs) are discussed by simulating triple single-electron transistors (TSETs) with triple qubits.