Security of entanglement-based quantum key distribution with practical   detectors
  We prove the unconditional security of an entanglement-based quantum-key-distribution protocol using detectors that respond to multiple modes of light and cannot distinguish between one from two or more photons. Even with such practical detectors, any defect in the source is automatically detected as an increase in the error rate or in the rate of double clicks. 
Masato Koashi, Yoritoshi Adachi, Takashi Yamamoto, and Nobuyuki Imoto