Quench dynamics of fermion-parity switches in a Josephson junction
Abstract
A Josephson junction may be driven through a transition where the superconducting condensate favors an odd over an even number of electrons. At this switch in the ground-state fermion parity, an Andreev bound state crosses through the Fermi level, producing a zero-mode that can be probed by a point contact to a grounded metal. We calculate the time-dependent charge transfer between superconductor and metal for a linear sweep through the transition. One single quasiparticle is exchanged with charge Q depending on the coupling energies γ1,γ2 of the metal to the Majorana operators of the zero-mode. For a single-channel point contact, Q equals the electron charge e in the adiabatic limit of slow driving, while in the opposite quenched limit Q=2eγ1γ2/(γ1+γ2) varies between 0 and e. This provides a method to produce single charge-neutral quasiparticles on demand.