Speaker
Description
Magnetic impurities in s-wave superconductors lead to spin-polarized Yu-Shiba-Rusinov (YSR) in-gap states. Chains of magnetic impurities offer one of the most viable routes for the realization of Majorana bound states, which hold promise for topological quantum computing. However, this ambitious goal looks distant, since no quantum coherent degrees of freedom have yet been identified in these systems. To fill this gap, we propose an effective two-level system, a YSR qubit, stemming from two nearby impurities. Using a time-dependent wave-function approach, we derive an effective Hamiltonian describing the YSR-qubit evolution as a function of the distance between the impurity spins, their relative orientations, and their dynamics. We show the coherent control and readout of the YSR qubit using both the dynamics of the magnetic impurities and circuit quantum electrodynamics (cQED) architecture. We further show that YSR qubits can serve as a controllable interface to Majorana qubits, enabling fast operations while topological degrees of
freedom provides robust quantum memory.