Superconducting Quantum Hall Hybrid Interface State Mediated Quantum Entanglement

Project: Research

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Hybrid, low-dimensional systems are at the forefront of modern scientific research. Moreover, recent interests in novel topological states of matter have reinvigorated the field, and placed heavy interest on combining one- and two-dimensional materials with superconductivity. Graphene still remains a flagship material to form such hybrid systems as is evidenced by the strong ongoing effort towards making devices, focused in particular on breakthroughs in quantum computing and quantum information. This proposal will focus on a key element in quantum information: a reliable, on-chip source of entangled electrons. Successful previous works have used a nanowire-based, superconductor-two quantum dot Cooper Pair splitter design to generate pairs of entangled electrons. However, while efficiency has been demonstrated, such devices lack consistent tunability, scalability, and entangled pairs have only been generated at distances of few 100nm apart. Graphene devices even based on the same superconductor-two quantum dot design are capable of overcoming all of the above issues. Already, design-based tunability has been demonstrated. The roadmap towards scalability and long distance entangled pair separation is clear; with electron pair separations over 1 micron easily supported by theory. However, recent demonstration of superconductivity in the quantum Hall (QH) regime opens up a possibility of a different entangler design; one capable of generating entangled electron pairs with high efficiency on macroscopic scales. In QH regime the supercurrent is supported by counter propagating currents contained in opposite edges of a graphene crystal. Superconductivity and entanglement is facilitated via hybrid modes along the superconductor-graphene interface. Accessing the edge states would give one a source of entangled electrons. Previous work on conventional Josephson junction devices already showed that the superconducting QH edge states can be separated by up to 4.5um. While not macroscopic, such distances are already on the order of the size of modern 4-5 qubit systems. Moreover, separation distances over 100 micrometers have been postulated. This project’s ultimate goal is to demonstrate such superconducting quantum Hall edge state-based entangler. Starting with the conventional design, the project first aims to demonstrate super-micron entanglement; and to achieve near unity efficiency allowing us to evaluate the degree of entanglement. Further focus will be on QH edge state devices. The superconducting edges will be accessed by normal-metal contacts. Initially, entangled pair generation will be measured via conduction resonances corresponding to resonances of the hybrid modes. Finally, shot-noise measurements will be performed to demonstrate Cooper Pair splitting.


Project number9048125
Grant typeECS
Effective start/end date1/01/19 → …