Fig. 2
From: Experimental demonstration of quantum walks with initial superposition states
Schematic of the experimental setup for a quantum walk in the polarization space, in which D0 is a single-photon detector and D1 (D2) represents the standard polarization analysis detector. A pair of photons are generated in the BBO crystal. One photon is detected directly by D0 as the trigger and another photon is adopted to make the DTQW. The initial states of the coin and the walker are prepared in the light-yellow block. The DTQW is realized with two optical loops. The photons experience different steps of the DTQW and can be distinguished by their arrival times at D1 or D2 after a trigger event. PBS polarizing beam splitter
