Long-range coupling mechanism and architecture for superconducting flux qubits

Devising a scalable mechanism enabling long-range interaction of qubits in a solid-state quantum computer is an important open problem. With only nearest neighbour interactions, gate error rates of order $10^{-7}$ or lower would be required to perform an arbitrarily large computation. If the right kinds of long- range interactions are available, gate error rates of order $10^ {-4}$, and possibly higher, would be acceptable. We discuss exactly what kinds of long-range interactions are required, present a simple mechanism for superconducting flux qubits, a scalable architecture based on this mechanism, and discuss the challenges on the road to physical realisation.