Spin-Orbit Interaction Enabled High-Fidelity Two-Qubit Gates

TL;DR

This paper investigates how spin-orbit interaction affects two-qubit gates in semiconductor spin qubits, revealing optimal operation points and new gate types enabled by SOI, with implications for high-fidelity quantum computing.

Contribution

It develops a microscopic Hamiltonian for SOI in spin qubits and identifies optimal conditions and novel gates enabled by SOI, advancing quantum gate design.

Findings

Existence of SOI nodes with enhanced gate fidelity.

Discovery of reflection and direct CNOT gates enabled by SOI.

Analysis of fidelities achievable for the direct CNOT gate.

Abstract

We study the implications of spin-orbit interaction (SOI) for two-qubit gates (TQGs) in semiconductor spin qubit platforms. SOI renders the exchange interaction governing qubit pairs anisotropic, posing a serious challenge for conventional TQGs derived for the isotropic Heisenberg exchange. Starting from microscopic level, we develop a concise computational Hamiltonian that captures the essence of SOI, and use it to derive properties of the rotating-frame time evolutions. Two key findings are made. First, for the controlled-phase/controlled-Z gate, we show and analytically prove the existence of ``SOI nodes'' where the fidelity can be optimally enhanced, with only slight modifications in terms of gate time and local phase corrections. Second, we discover and discuss novel two-qubit dynamics that are inaccessible without SOI -- the reflection gate and the direct controlled-not gate. The relevant conditions and achievable fidelities are studied for the direct controlled-not gate.