Coherent spin-valley oscillations in silicon

TL;DR

This paper demonstrates that the valley degree of freedom in silicon quantum dots can be harnessed for coherent control of electron spins, turning a potential obstacle into a resource for quantum computing.

Contribution

It shows that spin-valley coupling in silicon enables coherent manipulation of spin states without external ac magnetic or electric fields, a novel approach in silicon qubits.

Findings

Coherent control of single- and two-electron spin states achieved.

Valley degree of freedom used as a resource for quantum manipulation.

Demonstrated manipulation without ac magnetic or electric fields.

Abstract

Electron spins in silicon quantum dots are excellent qubits because they have long coherence times, high gate fidelities, and are compatible with advanced semiconductor manufacturing techniques. The valley degree of freedom, which results from the specific character of the Si band structure, is a unique feature of electrons in Si spin qubits. However, the small difference in energy between different valley levels often poses a challenge for quantum computing in Si. Here, we show that the spin-valley coupling in Si, which enables transitions between states with different spin and valley quantum numbers, enables coherent control of electron spins in Si. We demonstrate coherent manipulation of effective single- and two-electron spin states in a Si/SiGe double quantum dot without ac magnetic or electric fields. Our results illustrate that the valley degree of freedom, which is often regarded as an inconvenience, can itself enable quantum manipulation of electron spin states.