Engineering Spin‐Orbit Interactions in Silicon Qubits at the Atomic‐Scale

Abstract

Spin‐orbit interactions arise whenever the bulk inversion symmetry and/or structural inversion symmetry of a crystal is broken providing a bridge between a qubit's spin and orbital degree of freedom. While strong interactions can facilitate fast qubit operations by all‐electrical control, they also provide a mechanism to couple charge noise thereby limiting qubit lifetimes. Previously believed to be negligible in bulk silicon, recent silicon nano‐electronic devices have shown larger than bulk spin‐orbit coupling strengths from Dresselhaus and Rashba couplings. Here we show that with precision placement of phosphorus atoms in silicon along the [110] direction (without inversion symmetry) or [111] direction (with inversion symmetry) we can achieve a wide range of Dresselhaus and Rashba coupling strength from zero to 1113 × 10⁻¹³eV‐cm. We show that with precision placement of phosphorus atoms we can therefore change the local symmetry (C_2v, D_2d and D_3d) to engineer spin‐orbit interactions. Since spin‐orbit interactions affect both qubit operation and lifetimes, understanding their impact is essential for quantum processor design.

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