Real-time shot-noise-limited differential photodetection for atomic   quantum control
  We demonstrate high-efficiency, shot-noise-limited differential photodetection with real-time signal conditioning, suitable for feedback-based quantum control of atomic systems. The detector system has quantum efficiency of 0.92, is shot-noise limited from 7.4 x 10^5 to 3.7 x 10^8 photons per pulse, and provides real-time voltage-encoded output at up to 2.3 Mpulses per second. 
F. Martin Ciurana, G. Colangelo, Robert J. Sewell, and M.W. Mitchell
physics.optics physics.atom-ph quant-ph