Spectroscopy of Spin-Split Andreev Levels in a Quantum Dot with Superconducting Leads
Arno Bargerbos (Kavli institute of nanoscience Delft, TU Delft - QRD/Kouwenhoven Lab, TU Delft - QuTech Advanced Research Centre)
Marta Pita-Vidal (TU Delft - QRD/Kouwenhoven Lab, TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft)
Rok Žitko (Jozef Stefan Institute, University of Ljubljana)
Lukas J. Splitthoff (TU Delft - QRD/Kouwenhoven Lab, TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft)
Lukas Grünhaupt (TU Delft - QuTech Advanced Research Centre, TU Delft - QRD/Kouwenhoven Lab, Kavli institute of nanoscience Delft)
Jaap J. Wesdorp (TU Delft - QuTech Advanced Research Centre, TU Delft - QRD/Kouwenhoven Lab, Kavli institute of nanoscience Delft)
Yu Liu (University of Copenhagen)
Leo P. Kouwenhoven (TU Delft - QN/Kouwenhoven Lab, TU Delft - QuTech Advanced Research Centre, Kavli institute of nanoscience Delft)
Ramón Aguado (Instituto de Ciencia de Materiales de Madrid (ICMM))
Christian Kraglund Andersen (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre, TU Delft - Andersen Lab)
Angela Kou (University of Illinois at Urbana Champaign)
Bernard van Heck (Sapienza University of Rome, Universiteit Leiden)
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Abstract
We use a hybrid superconductor-semiconductor transmon device to perform spectroscopy of a quantum dot Josephson junction tuned to be in a spin-1/2 ground state with an unpaired quasiparticle. Because of spin-orbit coupling, we resolve two flux-sensitive branches in the transmon spectrum, depending on the spin of the quasiparticle. A finite magnetic field shifts the two branches in energy, favoring one spin state and resulting in the anomalous Josephson effect. We demonstrate the excitation of the direct spin-flip transition using all-electrical control. Manipulation and control of the spin-flip transition enable the future implementation of charging energy protected Andreev spin qubits.