 This protocol uses the quantum phenomenon whereby the possibility that a photon can be sent has an effect even when it isn't sent.So-called interaction-free measurement also uses this quantum effect, as for example in the bomb testing problem, whereby you can determine which bombs are not duds without setting them off, except in a counterfactual sense.Quantum cryptography was proposed first by Stephen Wiesner, then at Columbia University in New York, who, in the early 1970s, introduced the concept of quantum conjugate coding.