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QI: Fachverband Quanteninformation

QI 13: Implementations: Superconducting Qubits

QI 13.9: Vortrag

Freitag, 9. September 2022, 12:00–12:15, H8

Magnetic field dependence of the quasiparticle parity lifetime in 3D transmons with thin-film Al−AlO_x−Al Josephson junctions — •Jonas Krause¹, Lucas Jannsen¹, Christian Dickel¹, Elmore Vaal¹, Michel Vielmetter¹, Jurek Frey², Felix Motzoi³, Shai Machness², Kelvin Loh⁴, Michiel Adriaan Rol⁴, Gianluigi Catelani⁵, and Yoichi Ando¹ — ¹Physics Institute II, University of Cologne — ²Quantum Computing Analytics (PGI 12), Forschungszentrum Jülich — ³Institute of Quantum Control (PGI-8), Forschungszentrum Jülich — ⁴Orange Quantum Systems — ⁵JARA Institute for Quantum Information (PGI-11), Forschungszentrum Jülich

Magnetic-field resilient superconducting circuits enable quantum sensing applications, hybrid quantum computing architectures, as well as studying flux noise and quasiparticle loss. Placing a thin-film aluminum transmon in a 3D copper cavity, we can measure its quasiparticle parity lifetime over a large range of magnetic fields, with in-plane fields approaching 1T. The magnetic field reduces the Josephson Energy E_J, while the charging energy E_C is virtually unaffected. The transmon exhibits a parity-dependent frequency splitting. We are working on optimal control techniques for fast parity-selective gates which together with single-shot readout allow measuring the parity lifetime. The magnetic-field dependence of the parity lifetime is of interest for future topological qubits, which rely on combining superconductors with magnetic fields; additionally, it could improve the understanding quasiparticle loss in conventional superconducting qubits.