Figure 2

Schematic of the experimental setup. Single photon source: PPKTP nonlinear crystal enclosed in an oven is pumped by 405 nm laser. A half wave plate (H₁) is used to control pump polarization and lens (L₁ of 300 mm) is used to focus the laser beam into the center of the crystal. Lens (L₂ of 35 mm) is used collimate the down-converted photons. A bandpass interference filter (IF of 810 ± 10 nm) is used for filtering the pump. Polarization beam splitter (PBS₁) is used to separate generated orthogonally polarized photons. QRNG unit: \(|V\rangle \) polarized single photons are coupled into single-mode optical fiber (SMF). Three non-polarizing 50:50 beam splitters (BS₁-BS₃) are used to generate two-bit random numbers. Four single photon counting modules (D₁-D₄) are used to detect single photons at the output of BS₂ and BS₃. The output of the SPCMs are fed to a time-correlated single photon counter (Time Tagger)