Two photons in an entangled state of polarization is created by parametric down conversion of a pump light. A first photon of the two photons is sent to a sender while a second photon of the two photons is sent to a receiver. The second photon is divided into a first component and a second component. The receiver makes the first component interact with an isotropic nonlinear optical medium. The sender selects the angle of a polarizer according to a signal that he wants to transmit to the receiver and measures the first photon after it passes the polarizer. The receiver mixes the first component and the second component by a half beam splitter. The receiver knows the signal by measuring the probability of photon detection of two output lights from the half beam splitter.