Measurement of Enhanced Spin‐Orbit Coupling Strength for Donor‐Bound Electron Spins in Silicon

While traditionally considered a deleterious effect in quantum dot spin qubits, the spin‐orbit interaction is recently being revisited as it allows for rapid coherent control by on‐chip AC electric fields. For electrons in bulk silicon, spin‐orbit coupling (SOC) is intrinsically weak, however, it can be enhanced at surfaces and interfaces, or through atomic placement. Here it is showed that the strength of the spin‐orbit coupling can be locally enhanced by more than two orders of magnitude in the manybody wave functions of multi‐donor quantum dots compared to a single donor, reaching strengths so far only reported for holes or two‐donor system with certain symmetry. These findings may provide a pathway toward all‐electrical control of donor‐bound spins in silicon using electric dipole spin resonance (EDSR). A significant enhancement in spin‐orbit coupling (SOC) within multi‐donor silicon quantum dots is demonstrated, showing SOC strengths up to 40 µeV, surpassing previous benchmarks by two orders of magnitude. This advancement paves the way for precise all‐electrical control of donor‐bound spins and improved coupling to superconducting resonators, marking a crucial step forward in quantum computing.