Kondo-based Qubits for Topological Quantum Computation

Abstract: We propose to use residual parafermions of the overscreened Kondo effect for topological quantum computation. A superconducting proximity gap of $\Delta<T_K$ can be utilized to isolate the parafermion from the continuum of excitations and stabilize the non-trivial fixed point. We use weak-coupling renormalization group, dynamical large-N technique and bosonization to show that the residual entropy of multichannel Kondo impurities survives in a superconductor. We find that while (in agreement with recent numerical studies) the non-trivial fixed point is unstable against intra-channel pairing, it is robust in presence of a finite inter-channel pairing. Based on this observation, we suggest a superconducting charge Kondo setup for isolating and detecting the Majorana fermion in the two-channel Kondo system.