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

Controlling decoherence is the biggest challenge in efforts to develop quantum information hardware 1 , 2 , 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 , 5 , 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. Spin doublets of holes in nanowires with a germanium core and a silicon shell can be manipulated in fast-gated double quantum dots to create quantum bits with long spin lifetimes.