A natural heavy-hole flopping mode qubit in germanium

TL;DR

This paper proposes a natural heavy-hole flopping mode qubit in germanium that leverages cubic Rashba spin-orbit interaction, enabling fast, tunable quantum gates without complex magnetic field gradients.

Contribution

It introduces a heavy-hole system in germanium utilizing cubic Rashba SOI to realize flopping mode qubits, eliminating the need for synthetic spin-orbit interactions.

Findings

Achieves nanosecond-range one- and two-qubit gate times.

Demonstrates highly tunable spin coupling strengths.

Proposes a simplified experimental setup for heavy-hole qubits.

Abstract

Flopping mode qubits in double quantum dots (DQDs) allow for coherent spin-photon hybridization and fast qubit gates when coupled to either an alternating external or a quantized cavity electric field. To achieve this, however, electronic systems rely on synthetic spin-orbit interaction (SOI) by means of a magnetic field gradient as a coupling mechanism. Here we theoretically show that this challenging experimental setup can be avoided in heavy-hole (HH) systems in germanium (Ge) by utilizing the sizeable cubic Rashba SOI. We argue that the resulting natural flopping mode qubit possesses highly tunable spin coupling strengths that allow for one- and two-qubit gate times in the nanosecond range when the system is designed to function in an optimal operation mode which we quantify.