Via the arxiv blog:
Everyone is going graphene crazy at the moment! This scheme suggests using a Graphene nanoribbon in a zigzag shape such that electrons (or holes) are localized at the two corners of the zigzag, and the interaction between the spins can then be used to demonstrate coherent properties of the system. Each ribbon then forms a quantum dot structure such that adjacent ribbons can be coupled together with varying strength of interaction.
Scaling this sounds difficult though, especially as the current state of the art graphene manipulation techniques tend to involve the use of sellotape 😉