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TT: Fachverband Tiefe Temperaturen

TT 11: Superconductivity: Poster

TT 11.41: Poster

Montag, 17. März 2025, 15:00–18:00, P4

Design of fluxonium qubits inductively coupled to granular aluminum based readout resonators — •Li-Wei Chang, Asen Georgiev, Fabian Kaap, Sergey Lotkhov, Mark Bieler, and Lukas Gruenhaupt — Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany

The fluxonium qubit is a specific type of superconducting qubit, which has garnered significant interest due to its coherence time in the milli-second range, high gate fidelities on the order of 99.9%, and a large anharmonicity up to several GHz. Recent years have also seen a surge in material studies related to this type of qubit, with a particular focus on high kinetic inductance materials such as granular aluminum (grAl). Three basic components form a fluxonium qubit: a Josephson junction, a capacitor, and a so-called superinductor with an impedance larger than the resistance quantum R_Q = ℏ / 4e². We discuss our circuit parameters chosen via numerical simulations to implement a fluxonium with a transition frequency of 0.6 GHz ∼ 12 GHz depending on the external magnetic field. To enable dispersive readout, we employ a granular aluminum based readout resonator. This configuration not only provides substantial inductance but also allows inductive coupling to the qubit. We present our methodology to design the circuit parameters, including the dispersive shift, quality factor, and T1 Purcell decay

Keywords: Qubits; fluxonium