npj Quantum Information, Published online: 17 October 2024; doi:10.1038/s41534-024-00897-8
Modeling of planar germanium hole qubits in electric and magnetic fields
Hole-based spin qubits in strained planar germanium quantum wells have received considerable attention due to their favorable properties and remarkable experimental progress.
The sizeable spin-orbit interaction in this structure allows for efficient qubit operations with electric fields. However, it also couples the qubit to electrical noise.
In this work, the team performs simulations of a heterostructure hosting these hole spin qubits. They have solved the effective mass equations for a realistic heterostructure, provide a set of analytical basis wavefunctions, and compute the effective g-factor of the heavy-hole ground state.
Their investigations reveal a strong impact of highly excited light-hole states located outside the quantum well on the g-factor. They found that sweet spots, points of operations that are least susceptible to charge noise, for out-of-plane magnetic fields are shifted to impractically large electric fields.
However, for magnetic fields close to in-plane alignment, partial sweet spots at low electric fields are recovered. Furthermore, sweet spots with respect to multiple fluctuating charge traps can be found under certain circumstances for different magnetic field alignments.
This work will be helpful in understanding and improving the coherence of germanium hole spin qubits.