Fig. 3: Intercity quantum key distribution using telecom C-band single photons from a semiconductor source, transmitted over the deployed fibre with a loss of 25.49 dB.
From: High-rate intercity quantum key distribution with a semiconductor single-photon source
a Time-resolved QD emission for different CRs. b Blinking-corrected, second-order auto-correlation at zero time delay g(2)(0) as a function of measurement time recorded in Braunschweig for the CRs 
76 MHz, 
228 MHz, 
608 MHz and 
1.06 GHz. Each data point represents 0.5 h of measurement time, and no time gating was applied. The dashed lines show the average g(2)(0) over the whole measurement with values of 0.108 ± 0.005, 0.056 ± 0.002, 0.143 ± 0.002 and 0.185 ± 0.002. Insets: normalised (NORMD) second-order correlation histograms for the CRs of 228 MHz and 1064 MHz. c Truth table of the polarisation encoded BB84 protocol. The correlation histograms in each column are normalised by the decoded coincidences resulting from the encoded states (diagonal histograms in the table). d A-SKR, F-SKR and QBER over time for different encoding bases \(\left\{X,Z\right\}\) at a fixed CR of 228 MHz. Each data point in the solid lines represents the average of 1 min. The colour-coded inset graphs on the right-hand side shows the average asymptotic, finite SKR, as well as QBER over the 35 h- key transmission time with and without the 2-D temporal filter. The SKBs per pulse are evaluated to be (4.797 ± 0.011) × 10−5, (4.464 ± 0.011) × 10−5, (2.349 ± 0.031) × 10−5 and (1.867 ± 0.005) × 10−5. The average QBER (dashed line) decreases from (1.041 ± 0.004)% to (0.646 ± 0.002)%
