A dressed singlet-triplet qubit in germanium

• URL: http://arxiv.org/abs/2501.14627v1
• Date: Fri, 24 Jan 2025 16:44:58 GMT
• Title: A dressed singlet-triplet qubit in germanium
• Authors: Konstantinos Tsoukalas, Uwe von Lüpke, Alexei Orekhov, Bence Hetényi, Inga Seidler, Lisa Sommer, Eoin G. Kelly, Leonardo Massai, Michele Aldeghi, Marta Pita-Vidal, Nico W. Hendrickx, Stephen W. Bedell, Stephan Paredes, Felix J. Schupp, Matthias Mergenthaler, Gian Salis, Andreas Fuhrer, Patrick Harvey-Collard,
• Abstract summary: In semiconductor hole spin qubits, low magnetic field operation extends the coherence time but proportionally reduces the gate speed. In contrast, singlet-triplet (ST) qubits are primarily controlled by the exchange interaction. By modulating germanJ$, we achieve resonant driving of the ST qubit.
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• Abstract: In semiconductor hole spin qubits, low magnetic field ($B$) operation extends the coherence time ($T_\mathrm{2}^*$) but proportionally reduces the gate speed. In contrast, singlet-triplet (ST) qubits are primarily controlled by the exchange interaction ($J$) and can thus maintain high gate speeds even at low $B$. However, a large $J$ introduces a significant charge component to the qubit, rendering ST qubits more vulnerable to charge noise when driven. Here, we demonstrate a highly coherent ST hole spin qubit in germanium, operating at both low $B$ and low $J$. By modulating $J$, we achieve resonant driving of the ST qubit, obtaining an average gate fidelity of $99.68\%$ and a coherence time of $T_\mathrm{2}^*=1.9\,\mu$s. Moreover, by applying the resonant drive continuously, we realize a dressed ST qubit with a tenfold increase in coherence time ($T_\mathrm{2\rho}^*=20.3\,\mu$s). Frequency modulation of the driving signal enables universal control, with an average gate fidelity of $99.64\%$. Our results demonstrate the potential for extending coherence times while preserving high-fidelity control of germanium-based ST qubits, paving the way for more efficient operations in semiconductor-based quantum processors.

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