Strong coupling between two spin ensembles via a large Josephson   junction
  We propose a method to achieve strong coupling between a spin ensemble and a large Josephson junctions (LJJ). Then, the strong coupling between two spin ensembles can be induced by a LJJ. A non-adiabatic holonomic single-qubit quantum gates is realized. Moreover, with the dispersive interaction between the spin ensembles and the LJJ, the high-fidelity two-qubit phase gate can be implemented with two spin ensembles within an operation time 0.41 ns and $\pi$ phase-swap gate can be realized within an operation time 103.11 ns with a high fidelity greater than 99%. 
Feng-Yang Zhang, Wenlin Li, Chui-Ping Yang
quant-ph