Induced superconductivity in fractional quantum Hall edge*

Topological superconductors (TS) represent a phase of matter whose properties are insensitive to local perturbations. This robustness renders TS suitable for application in quantum computing. The past decade has witnessed substantial progress towards a quantum bit using Majorana modes, the well-known non-Abelian modes in TS. However, because Majoranas lack a universal logic gate set, Majorana quantum bits are computationally limited. This important drawback can be overcome by parafermions, a novel set of non-Abelian modes whose array supports universal topological quantum computation. A primary route to synthesize parafermions involves inducing superconductivity in fractional quantum Hall (FQH) edge. Here we use high-quality van der Waals devices coupled to a narrow NbN which remains superconducting in the magnetic fields required for robust FQH. We find crossed Andreev reflection (CAR) across the narrow NbN that separates two counterpropagating FQH edges. Control experiments show that CAR vanishes with increasing temperature, excitation and magnetic field as expected from the theory. These results lay the groundwork for experimental parafermion research in condensed matter.