A scalable, tunable qubit, based on a clean DND or grain boundary D-D junction

TL;DR

This paper proposes a new type of solid-state qubit based on a ballistic DND or grain boundary D-D junction, leveraging unique properties like a doubly degenerate ground state and tunable potential barrier for quantum computing applications.

Contribution

It introduces a scalable, tunable qubit design utilizing DND or grain boundary D-D junctions with unique magnetic and phase properties, advancing solid-state quantum technology.

Findings

DND or grain boundary D-D junctions exhibit doubly degenerate ground states.

The sign of the superconducting phase difference acts as a quantum spin variable.

Designs allow for potential simultaneous operations of multiple qubits.

Abstract

Unique properties of a ballistic DND or grain boundary D-D junction, including doubly degenerate ground state with tunable potential barrier between the "up" and "down" states and non-quantized spontaneous magnetic flux, make it a good candidate for a solid state qubit. The role of quantum "spin" variable is played by the sign of equilibrium superconducting phase difference on the junction, which is revealed in the direction of spontaneous supercurrent flow in equilibrium. Possibilities of design-specific simultaneous operations with several integrated qubits are discussed.