A 16 quantum dot crossbar array in germanium

Quantum dots in semiconductors are a promising platform for quantum information. The steady advancement in the material growth and in the electrical control of gate-defined quantum dots in germanium quantum wells enabled the demonstration of quantum logic in a one-, then two- and recently in a four-spin qubit processor. Scaling up to larger quantum systems presents outstanding challenges such as solving the interconnect bottleneck caused by the high number of degrees of freedom of the circuits. Here, we take this step and demonstrate the operation of the first 4x4 quantum dot crossbar array. Despite the reduced input voltages, the shared control of plunger and barrier gates enables the definition of 16 quantum dots with similar occupancy and addressable interdot coupling. This result is a crucial milestone for scaling and controlling spin qubits in two dimensions.