Fig. 5: Overview of the different experimental configurations.
From: Telecom quantum photonic interface for a 40Ca+ single-ion quantum memory
a The output state is measured directly at the source. b One of the photons is frequency-converted before its detection. c 20 km of fiber is inserted between conversion and detection. d The 20 km fiber gets terminated with a retro-reflector. The back reflected photons get back-converted after 40 km of fiber and are extracted with a 50:50 fiber beamsplitter before their detection. The background colors correspond to the colors of the data points in Fig. 6.
