Gate-biased illumination enables low voltage operation of Si/SiGe quantum dot devices

Semiconductor quantum dot qubits are gate-voltage controlled, and therefore they are excellent candidates for in-cryostat control by cryo-CMOS electronics. However, such in-cryostat control places severe constraints on power, and for this reason it is advantageous to be able to run quantum dot qubits with low gate voltages. Here, we implement a method to change the operating voltages in-situ, and we demonstrate how to transform a quantum dot qubit with initial operating voltages over 500 mV to one that can be run with no gate voltage exceeding 100 mV. The method relies on illumination with near-infrared light in the presence of applied gate voltages. This enables the tuning of the device operating point on a gate-by-gate basis and is consistent with a model describing the modification of the trapped charge under each gate. We address relevant factors such as photocurrent saturation and gate size, and further discuss the effects of crosstalk resulting from the overlapping-gate architecture of the device. Employing this method, we achieve sub-100 mV tuning across all gates in the (1,1,1) charge configuration for qubit operation of the triple quantum dot device. This work is a promising step towards the realization of scalable and tunable quantum processors.