Kavli Affiliate: Menno Veldhorst
| First 5 Authors: John Rooney, Zhentao Luo, Lucas E. A. Stehouwer, Giordano Scappucci, Menno Veldhorst
| Summary:
Spin qubits in germanium gate-defined quantum dots have made considerable
progress within the last few years, partially due to their strong spin-orbit
coupling and site-dependent $g$-tensors. While this characteristic of the
$g$-factors removes the need for micromagnets and allows for the possibility of
all-electric qubit control, relying on these $g$-tensors necessitates the need
to understand their sensitivity to the confinement potential that defines the
quantum dots. Here, we demonstrate a $S-T_$ qubit whose frequency is a strong
function of the voltage applied to the barrier gate shared by the quantum dots.
We find a $g$-factor that can be approximately increased by an order of
magnitude adjusting the barrier gate voltage only by 12 mV. We attribute the
strong dependence to a variable strain profile in our device. This work not
only reinforces previous findings that site-dependent $g$-tensors in germanium
can be utilized for qubit manipulation, but reveals the sensitivity and
tunability these $g$-tensors have to the electrostatic confinement of the
quantum dot.
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