Hole-spin qubits in germanium beyond the single-particle regime

TL;DR

This paper theoretically explores three-hole qubits in germanium, showing they can outperform single-hole qubits with significantly higher Rabi frequencies and quality factors, expanding the potential of hole-spin qubits beyond single occupancy.

Contribution

It introduces a theoretical analysis of three-hole qubits in germanium, demonstrating performance improvements over single-hole qubits in common geometries.

Findings

Three-hole qubits can achieve Rabi frequency enhancements of up to two orders of magnitude.

Large improvements in qubit quality factors are observed with three-hole encoding.

Performance rivals that of single-hole qubits in strained and unstrained germanium systems.

Abstract

The intense simulation efforts on hole-spin qubits in germanium have so far focused primarily on singly occupied quantum dots. Here, we theoretically investigate three-hole qubits in germanium and demonstrate that their performance can rival that of single-hole qubits in both strained and unstrained systems. In particular, we find that -- in the widely used quasi-circular geometry -- a three-hole qubit encoding can yield enhancements of the Rabi frequencies of up to two orders of magnitude and a large advantage also in terms of quality factors.