Exchange anisotropies in microwave-driven singlet-triplet qubits

• URL: http://arxiv.org/abs/2408.03224v2
• Date: Mon, 25 Nov 2024 08:14:37 GMT
• Title: Exchange anisotropies in microwave-driven singlet-triplet qubits
• Authors: Jaime Saez-Mollejo, Daniel Jirovec, Yona Schell, Josip Kukucka, Stefano Calcaterra, Daniel Chrastina, Giovanni Isella, Maximilian Rimbach-Russ, Stefano Bosco, Georgios Katsaros,
• Abstract summary: Hole spin qubits are emerging as workhorses of quantum processors. Spin-orbit interaction causes non-uniformities in devices, resulting in locally varying qubit energies and site-dependent anisotropies. We report on microwave-driven singlet-triplet qubits in planar germanium.
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• Abstract: Hole spin qubits are rapidly emerging as the workhorse of semiconducting quantum processors because of their large spin-orbit interaction, enabling fast all-electric operations at low power. However, spin-orbit interaction also causes non-uniformities in devices, resulting in locally varying qubit energies and site-dependent anisotropies. While these anisotropies can be used to drive single-spins, if not properly harnessed, they can hinder the path toward large-scale quantum processors. Here, we report on microwave-driven singlet-triplet qubits in planar germanium and use them to investigate the anisotropy of two spins in a double quantum dot. We show two distinct operating regimes depending on the magnetic field direction. For in-plane fields, the two spins are largely anisotropic, and electrically tunable, which enables to measure all the available transitions; coherence times exceeding 3 $\mu$s are extracted. For out-of-plane fields, they have an isotropic response but preserve the substantial energy difference required to address the singlet-triplet qubit. Even in this field direction, where the qubit lifetime is strongly affected by nuclear spins, we find 400 ns coherence times. Our work adds a valuable tool to investigate and harness the anisotropy of spin qubits and can be implemented in any large-scale NxN device, facilitating the path towards scalable quantum processors.

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