Figure 10
From: A low cost, short range quantum key distribution system
The intermediate steps of correcting for fibre birefringence using quarter, quarter, half (QQH) wave plates. In this example, angles for the QQH wave plates were 66.2∘, 40.6∘, 77.2∘, respectively. Using Mueller matrices of polarizers, a predicted error rate of 5.6% is obtained. This is an upper limit. When we confine ourselves to measurements in the equatorial plane (V/H;D/A), and include postprocessing, a lower error rate is measured (see Sect. 5)