Topological Superconductivity in Graphene

ongoing

In recent years, a considerable stream of work from the condensed matter community has been focusing on hybrid systems coupling superconductors to various topological states of matter. Such a heterogeneous coupling is pivotal in enabling the emergence of new excitations –the Majorana or parafermion— that could be used as quantum bits (qubits) with unique properties of non-locality and immunity to external perturbations, essential to encode and manipulate quantum information in a robust and stable fashion. Nevertheless, topological insulators that can be efficiently hybridized with superconductors and enable reliable coherent manipulation are still missing. This project aims at demonstrating a new topological insulator, the quantum Hall topological insulator that emerges in graphene as an unusual quantum spin Hall phase, as the ideal platform for topological superconductivity. Its novelty hinges on an unprecedented substrate engineering that profoundly modifies the quantum Hall ground state of neutral graphene. The ensuing robust quantum Hall phase harbors spin-filtered, helical edge states that can be easily coupled to superconducting electrodes for investigating novel hybrid superconducting quantum circuits. The versatility of graphene enables designing locally gated quantum devices, tunnelling experiments, and coupling to a photon cavity for time-resolved spectroscopy to unveil Majoranas or parafermions in unprecedented fashion. Ultimately, quantum coherent manipulation of Majorana qubits in hybrid devices will be performed, providing a major breakthrough in the way of fault-tolerant quantum computers. Moreover, the identification of parafermions will constitute a considerable conceptual advance that will open a totally new horizon for topological superconductivity and quantum computing technologies.