  Solid-state qubits integrated on semiconductor substrates currently require
at least one wire from every qubit to the control electronics, leading to a
so-called wiring bottleneck for scaling. Demultiplexing via on-chip circuitry
offers an effective strategy to overcome this bottleneck. In the case of
gate-defined quantum dot arrays, specific static voltages need to be applied to
many gates simultaneously to realize electron confinement. When a
charge-locking structure is placed between the quantum device and the
demultiplexer, the voltage can be maintained locally. In this study, we
implement a switched-capacitor circuit for charge-locking and use it to float
the plunger gate of a single quantum dot. Parallel plate capacitors,
transistors and quantum dot devices are monolithically fabricated on a
Si/SiGe-based substrate to avoid complex off-chip routing. We experimentally
study the effects of the capacitor and transistor size on the voltage accuracy
of the floating node. Furthermore, we demonstrate that the electrochemical
potential of the quantum dot can follow a 100 Hz pulse signal while the dot is
partially floating, which is essential for applying this strategy in qubit
experiments.
