Quantum entanglement and quantum entanglement generation have played an important role in quantum information processing including quantum teleportation and quantum computation. Among these quantum systems of generation entanglement, cavity quantum electrodynamics system, in particular, the whispering-gallery mode (WGM)-type microcavity provides one of the most promising ones due to its ultrahigh quality Q-factor and highly confined ultrasmall mode volume V. On the other hand, it has been found out that the nitrogen-vacancy (NV) center in a diamond nanocrystal has extremely long electronic spin deoherence time even at room temperature. So NV centers have been considered as an excellent candidate for quantum information processing. 

Based on these achievements, Professor Wu Ying research group of fundamental photonics research team in Wuhan national laboratory for optoelectronics provide a new quantum system to generate maximum quantum entanglement, i.e., two NV centers coupling to a high-Q counterpropagating twin whispering-gallery modes of a microtoroidal resonator. We investigate the entanglement generation between two NV centers in diamond nanocyrstal. We calculate the concurrence using the microscopic master equation approach and discuss the influences of the coupling strength between WGMs, the distance between two NV centers , the frequency detuning between NV center and microresonator, and the initial state of the system on the dynamics of concurrence. It is found that the maximum entanglement between the two NV centers can be created by properly adjusting these controllable system parameters. Our results may provide further insight into future solid-state cavity quantum electrodynamics system for quantum information engineering. 
Part of this work has been supported by the National Natural Science Foundation of China under Grants No. 11004069, No. 11275074 and No. 91021011, by the Doctoral Foundation of the Ministry of Education of China under Grant No. 20100142120091, and by the National Basic Research Program of China under Contract No. 2012CB922103.  The paper was published in the Optics Express (Vol. 21, No. 3, 3501-3515) of Optical Society of America.