The signal and idler photons generated by a parametric down converter are highly correlated. We show that the information obtained from a photodetector monitoring the idler port can be used to open and close a shutter in the signal port in such a manner that an antibunched photon beam is produced.

• Received 27 February 1986

DOI:https://doi.org/10.1103/PhysRevA.34.3143