Princeton Lightwave of Cranbury, N.J., has licensed single-photon-detection technology from IBM Corp. of White Plains, N.Y. The detectors are a key component of quantum cryptography systems, which are being developed to enable secure communications in such areas as government and finance. They also have applications in scientific research and in optical and semiconductor test and measurement. The company will develop the technology by combining it with the InGaAs/InP avalanche photodiode that has been optimized for single-photon counting.