(a) The setup to measure K(t1,t2). The quartz plate (q) with the tiltable combination of quartz plates in the solid pane M represents the evolution environment (black bars represent the optic axes of the quartz). The final measurement basis was chosen by the polarizer (P). The photon was coupled by a multimode fibre to the single photon detector D1 equipped with a long pass lens (LP) in front of it. (b) The setup to measure K(t1,t3). Two equal settings of quartz plates of q and M are used to simulate the environment operators U and U’ in fig. 1. (c) The setup to measure K(t2,t3). The dashed pane containing a polarization beam splitter (PBS) and three half wave plates (HWP) with optic axes set at 22.5° was inserted at time t2. The single photon detector D2 is used to detect the photon in path 2.