The physics of a quantum impurity in a superconductor is governed by the fermionic parity and spin of the two possible ground states, doublet or singlet, and their corresponding Yu-Shiba-Rusinov subgap excitations. After an introduction about their role in hybrid superconductor/semiconductor nanowires containing quantum dots [1], I will focus on semiconducting nanowires fully wrapped by a superconductor where an external magnetic flux gives rise to new regimes hitherto unexplored [2].
In the second part, I will discuss the physics of a superconducting qubit whose Josephson energy is governed by a fully tunable quantum dot. Specifically, a circuit QED setup allows to probe both its ground state and quasiparticle dynamics, resulting in, arguably, the most in-depth experimental study of a superconducting quantum impurity to date [3]. These results hold promise for realizing Andreev qubits with long parity lifetimes.
[1] Lee et al Phys. Rev. Lett. 109, 186802 (2012); Žitko et al, Phys. Rev. B 91, 045441 (2015); Lee et al, Nature Nanotech., 9, 79-84 (2014).
[2] Valentini et al, Science 373, 82-88 (2021); Escribano et al, Phys. Rev. B 105, 045418 (2022).
[3] Bargerbos et al arXiv:2202.12754. PRX Quantum, in press.
Note the unusual day of the week.
The seminar is presential with parallel zoom stream: https://zoom.us/j/98286706234?pwd=bm1JUFVYcTJkaVl1VU55L0FiWDRIUT09
