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European Commission

Introduction to the project

Cooper pair splitter

SE2ND (Source of Entangled Electrons in Nano Devices) is an ambitious project granted by the FP7 FET-Open initiative of the European Commission. SE2ND is a joint effort of experimental and theoretical physicists to develop a highly efficient and continuous solid-state source of spatially separated spin-entangled electrons. A source of this kind, integrated with other electronic elements, will be of great importance in future quantum processors, where they provide, for example, the entanglement distribution required to synchronize quantum circuits, or enable secure communication.
The present proposal is based on entangled electron pairs that naturally occur in the ground state of a superconductor. The key target device of SE2ND is an electron-pair splitter with two defining key functions: 1) it ensures that pairs are emitted one by one, and 2) the two electrons of the pair are spatially separated into two different output channels, while maintaining their entanglement. Both objectives can be realized in carefully tuned double quantum dots. Hybrid double quantum dots are fabricated in high-quality low-dimensional materials (semiconducting nanowires, carbon nanotubes and graphene) and integrated together with superconducting injectors, serving as sources of the electron pairs, ferromagnetic elements and microwave cavities in order to determine the degree of pair splitting and electron entanglement. SE2ND explores the relevant fundamental physics, the material and fabrication parameters, optimize the splitting efficiency, assess the spin relaxation rate, coherence and the degree of entanglement to provide an optimized source with near unity efficiency in entanglement generation at a rate >100 Mega pairs / second. SE2ND extensively develops hybrid nanodevices which exploit the unique properties of quantum dots in proximity to superconductors and ferromagnetic materials, thereby providing a novel toolbox for electron-based quantum information technology, helping to maintain Europe at the forefront of this rapidly evolving field.