Gatemon Qubit\non a Germanium Quantum-Well Heterostructure

Gatemons are superconducting qubits resembling transmons,\nwith\na gate-tunable semiconducting weak link as the Josephson element.\nHere, we report a gatemon device featuring an aluminum microwave circuit\non a Ge/SiGe heterostructure embedding a Ge quantum well. Owing to\nthe superconducting proximity effect, the high-mobility two-dimensional\nhole gas confined in this well provides a gate-tunable superconducting\nweak link between two Al contacts. We perform Rabi oscillation and\nRamsey interference measurements, demonstrate the gate-voltage dependence\nof the qubit frequency, and measure the qubit anharmonicity. We find\nrelaxation times <i>T</i><sub>1</sub> up to 119 ns, and\nRamsey coherence times <i>T</i><sub>2</sub><sup>*</sup> up to 70 ns, and a qubit frequency gate-tunable\nover 3.5 GHz. The reported proof-of-concept reproduces the results\nof a very recent work [Sagi et al. Nat. Commun. 2024, 15, 6400] using similar Ge/SiGe heterostructures,\nthereby validating a novel platform for the development of gatemons\nand parity-protected cos(2ϕ) qubits.