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 parafermions— 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. Such quantum excitations could serve as new quantum bits for designing next generation of fault-tolerant quantum computers. Nevertheless, topological insulators that can be efficiently hybridized with superconductors and enable reliable coherent manipulation are still missing.
This project aims at demonstrating the quantum Hall topological insulator state that emerges in charge neutral graphene when subjected to a strong perpendicular magnetic field, as a new 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 will enable us designing locally gated quantum devices to demonstrate control of helical edge channels, tunnelling experiments, and time-resolved microwave spectroscopy to unveil Majoranas or parafermions in hybrid superconducting quantum Hall devices. 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.
