Towards correcting atmospheric beam wander via pump beam control in a   down conversion process
  Correlated photon pairs produced by a spontaneous parametric down conversion (SPDC) process can be used for secure quantum communication over long distances including free space transmission over a link through turbulent atmosphere. We experimentally investigate the possibility to utilize the intrinsic strong correlation between the pump and output photon spatial modes to mitigate the negative targeting effects of atmospheric beam wander. Our approach is based on a demonstration observing the deflection of the beam on a spatially resolved array of single photon avalanche diodes (SPAD-array). 
Christopher J. Pugh, Piotr Kolenderski, Carmelo Scarcella, Alberto   Tosi and Thomas Jennewein
quant-ph