Fig. 1. Experimental setup of the source-DI QRNG. (a) Entanglement source: the time–energy entangled photon pairs are generated from the Ti:PPLN waveguide pumped by a pulsed laser with a duration of 5 ns, which are separated by a PBS. (b) Measurement device: photons are passively selected for measurement $T_{\delta }$ or $D_{\delta }$ by a 90:10 beam splitter (BS) after being coupled to fiber in Alice and Bob sides. PC, polarization controller; FI, filter; C-BG, chirped Bragg grating; OC, optical circulator; SNSPD, superconducting nanowire single-photon detector; and TDC, time-to-digital converter.

Fig. 2. Photon coincidence counts (CCs) recorded for four measurement combinations of two observers (denoted as $A$ and $B$) in 10 s.

Fig. 3. Smooth entropy $H_{\text{low}}^{ϵ}(T_{\delta }^A|E{)}_{\rho }$ with respect to the frame size $N_d$ for different processing units $N_T^A$. The dotted lines represent the entropy evaluated from the experimental data. The red triangles represent optimal results.

Fig. 4. Autocorrelation coefficients of raw random data and final random data.

Fig. 5. Results of NIST statistical test suite.

Table 1. Features of our protocol as compared to the features of existing semi-DI QRNG protocols.