Electrostatic uniformity and two-dimensional quantum dot arrays in silicon

Engineering highly uniform two-dimensional quantum dot arrays might be an essential requirement for building a scalable quantum processor based on silicon spin qubits. Here we show tuneable tunnel couplings in a silicon 2x2 quantum dot array operated in the single electron regime. In such a device we can compensate fluctuations in the electrostatic environment by applying individual gate voltages for each quantum dot. However, scaling this approach to larger arrays would lead to excessive overheads in tuning and control electronics. Therefore, we developed a method to electrically increase the potential uniformity in heterostructure quantum wells. We demonstrate that pinch-off voltages in quantum dot devices can be tuned over hundreds of millivolts and that they remain stable for hours afterward. Applying our method, we homogenize the pinch-off voltages of the plunger gates in a linear array for four quantum dots and reduce their spread by one order of magnitude. This work offers a new tool for the tuning of spin qubit devices providing perspectives for the implementation of scalable spin qubit arrays.