Circuit QED with Hole-Spin Qubits in Ge/Si Nanowire Quantum Dots

TL;DR

This paper proposes a fast, electrically controlled quantum computing platform using hole spins in Ge/Si nanowire quantum dots, enabling rapid single- and two-qubit gates with high noise resilience.

Contribution

It introduces a novel Ge/Si nanowire quantum dot setup for universal quantum computing with electrically tunable qubit interactions and high-speed gate operations.

Findings

Single-qubit gates with <100 ps spin-flip times.

Entangling gates below 20 ns operation time.

Qubits are insensitive to charge noise and phonons.

Abstract

We propose a setup for universal and electrically controlled quantum information processing with hole spins in Ge/Si core/shell nanowire quantum dots (NW QDs). Single-qubit gates can be driven through electric-dipole-induced spin resonance, with spin-flip times shorter than 100 ps. Long-distance qubit-qubit coupling can be mediated by the cavity electric field of a superconducting transmission line resonator, where we show that operation times below 20 ns seem feasible for the entangling square-root-of-iSWAP gate. The absence of Dresselhaus spin-orbit interaction (SOI) and the presence of an unusually strong Rashba-type SOI enable precise control over the transverse qubit coupling via an externally applied, perpendicular electric field. The latter serves as an on-off switch for quantum gates and also provides control over the g factor, so single- and two-qubit gates can be operated independently. Remarkably, we find that idle qubits are insensitive to charge noise and phonons, and we discuss strategies for enhancing noise-limited gate fidelities.