Kavli Affiliate: Menno Veldhorst
| First 5 Authors: Cecile X. Yu, Cecile X. Yu, , ,
| Summary:
Germanium spin qubits exhibit strong spin-orbit interaction, which allow for
high-fidelity qubit control, but also provide a strong dependence on the
magnetic field. Superconducting vector magnets are often used to minimize
dephasing due to hyperfine interactions and to maximize spin control, but these
compromise the sample space and thus challenge scalability. Here, we explore
whether a permanent magnet outside the cryostat can be used as an alternative.
Operating in a hybrid mode with an internal and external magnet, we find that
we can fine-tune the magnetic field to an in-plane orientation. We obtain a
qubit dephasing time T2*=13 microseconds, Hahn-echo times T2H=88 microseconds,
and an average single-qubit Clifford gate fidelity above 99.9%, from which we
conclude that room temperature magnets allow for high qubit performance.
Furthermore, we probe the qubit resonance frequency using only the external
magnet, with the internal superconducting magnet switched off. Our approach may
be used to scale semiconductor qubits and use the increased sample space for
the integration of cryogenic control circuitry and wiring to advance to
large-scale quantum processors.
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