Nico W Hendrickx

Quantum computers could eventually solve problems far beyond the reach of classical computers. But to make large-scale quantum systems possible, we need to drastically increase the number of qubits. Spins in gate-defined quantum dots—tiny regions in semiconductors where individual electrons are trapped—are a strong candidate for this scaling. However, controlling interactions between these qubits requires a dense web of wiring.

Hole spin qubits in group-IV semiconductors, especially Ge and Si, are actively investigated as platforms for ultrafast electrical spin manipulation thanks to their strong spin-orbit coupling. Nevertheless, the theoretical understanding of spin dynamics in these systems is in the early stages of development, particularly for in-plane magnetic fields as used in the vast majority of experiments.

A four-qubit quantum processor based on germanium hole spin quantum dots is presented. Universal quantum logic is demonstrated on qubits that are positioned in a two-by-two grid, revealing that spin qubits can be coupled in two dimensions. A two-by-two qubit quantum processor based on germanium hole spin quantum dots.