Figure 2. System architecture for single-photon decision maker and schematic of experimental setup.

The excitation laser excites a nitrogen-vacancy in a diamond crystal, and the emitted single photon passes through an immersion objective, high-pass filter (F), polarizer, half-wave plate, and PBS and is detected either in Ch.0 or Ch.1. The photon detection is immediately associated with the decision of which machine to play. On the basis of the betting results, the polarization adjuster (PA) controls the orientation of the half-wave plate using a rotary positioner.