Cryptography Reference
In-Depth Information
87. Despite their name, polarization maintaining fibers do not maintain any arbi-
trary polarization state. Only light polarized along one of the fiber's birefrin-
gence axes is maintained.
88. The QKD setup uses standard 50% couplers instead of the variable couplers
and the switches.
89. A Faraday mirror is a 90-degree Faraday rotator followed by a mirror. The
outcoming light is thus orthogonally polarized with respect to the ingoing
light. This is true whatever the incoming polarization state. Moreover, if a fiber
link is connected to a Faraday mirror, the outcoming light is still orthogonally
polarized independently of the polarization evolution inside the fiber [1, 7].
90. Here we assume that the collection efficiency for the photon traveling towards
Bob is 1. In practice, a more realistic value is
0.70.
91. Note that these results are not in contradiction with relativity.
92. To be precise, the assumption of independence only holds when the two pairs
are not created simultaneously within their coherence lengths [32], a condition
that is easily fulfilled experimentally.
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