Modelling of planar germanium hole qubits in electric and magnetic fields

Kavli Affiliate: Menno Veldhorst

| First 5 Authors: Chien-An Wang, Ercan Ekmel, Mark Gyure, Giordano Scappucci, Menno Veldhorst

| Summary:

Hole-based spin qubits in strained planar germanium quantum wells have
received considerable attention due to their favourable 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, we perform
simulations of a heterostructure hosting these hole spin qubits. We solve the
effective mass equations for a realistic heterostructure, provide a set of
analytical basis wave functions, and compute the effective g-factor of the
heavy-hole ground-state. Our investigations reveal a strong impact of highly
excited light-hole states located outside the quantum well on the g-factor. We
find 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 coherence of germanium
hole spin qubits.

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