Hole spin relaxation in Ge-Si core-shell nanowire qubits

Controlling decoherence is the biggest challenge in efforts to develop quantum information hardware(1-3). Single electron spins in gallium arsenide are a leading candidate among implementations of solid-state quantum bits, but their strong coupling to nuclear spins produces high decoherence rates(4-6). Group IV semiconductors, on the other hand, have relatively low nuclear spin densities, making them an attractive platform for spin quantum bits. However, device fabrication remains a challenge, particularly with respect to the control of materials and interfaces(7). Here, we demonstrate state preparation, pulsed gate control and charge-sensing spin readout of hole spins confined in a Ge-Si core-shell nanowire. With fast gating, we measure T-1 spin relaxation times of up to 0.6 ms in coupled quantum dots at zero magnetic field. Relaxation time increases as the magnetic field is reduced, which is consistent with a spin-orbit mechanism that is usually masked by hyperfine contributions.