Valentin John

Spin qubits in semiconductor quantum dots offer a promising route toward a quantum computer with millions of qubits. Nevertheless, considering that today's quantum processors require more than one terminal per qubit, scaling up from a few- to a million-qubit systems poses massive interconnectivity and control challenges. Here, inspired by memory architectures in classical electronics, we take the step from quantum devices controlled with such a brute-force approach to architectures with shared-control terminals for qubit energies and couplings. With this approach, we establish a 16 quantum dot crossbar array in planar germanium. The crossbar technology enables a sublinear scaling of the control terminals with the quantum dots counts, crucial for scalability prospects.

Furthermore, thanks to the heterostructure's low disorder, we can isolate an odd number of charges in all 16 quantum dots, a prerequisite for spin qubit operations. Finally, we demonstrate a proof-of-principle method to achieve addressable exchange coupling in a quantum dots shared-control architecture. These results represent a milestone for scaling and controlling semiconductor qubits in two dimensions.