Physicists have realized a quantum gambling machine using optical elements. From a helium-neon laser, a polarizer generates a single photon in a definite polarization state (horizontal or vertical). Then, Alice uses half wave plate 1 to transfer the definite state into a superposition state to alter the probability of the photon’s destination. The beam is split in the calcite beam splitter into beams A and B. Then Bob splits beam B with half wave plate 3 to influence the photon’s destination, and the second calcite beam splitter superposes beams B’ and A. Finally, three detectors labeled D1, D2, and D3 detect the photon in state B, B’, or A, respectively. Credit: Zhang, et al.