Remarkable Prospect for Quantum-Dot-Coupled Tin Qubits in Silicon

Abstract

Spin-1/2^{119}Sn nuclei in a silicon semiconductor could make excellent qubits. Nuclear spins in silicon are known to have long coherence times. Tin is isoelectronic with silicon, so we expect that electrons can easily shuttle from one Sn atom to another to propagate quantum information via a hyperfine interaction that we predict, from all-electron linearized augmented plane-wave density-functional-theory calculations, to be roughly 10 times larger than that of intrinsic ^{29}Si. A hyperfine-induced electron-nuclear controlled-phase (e-n-CPhase) gate operation, generated (up to local rotations) by merely holding an electron at a sweet spot of maximum hyperfine strength for a specific duration of time, is predicted to be exceptionally resilient to charge or voltage noise. Diabatic spin flips are suppressed with a modest magnetic field (>15mT for <10^{−6} flip probabilities) and nuclear-spin-bath noise may be avoided via isotopic enrichment or mitigated using dynamical decoupling or through monitoring and compensation. Combined with magnetic resonance control, this operation enables universal quantum computation.