Cryptography Reference
In-Depth Information
EOM
300mm
PBS
λ
/2
balanced
detector
Figure 5.11
Schematic view of Bob's setup, using an electro-optical modulator to
change between
S
2
and
S
3
measurement.
focusing lens (see Figure 5.12). It transmits 52% of the incoming light and
reflects 48%. The reflected light is retarded with a quarter-wave plate, to mea-
sure its
S
3
parameter on a second detector, similar to the one described above.
The remaining light is detected by the initial detector to give a measurement
of the
S
2
parameter. Both detectors can be read out simultaneously. Figure 5.10
shows the combination of both setups that was used in the experiment as a
reciever setup enabling us to make different performance tests.
300mm
PBS
BS
λ
/4a
balanced
detector
λ
/2
PBS
balanced
detector
Figure 5.12
Schematic view of Bob's setup, using two detection setups to measure
simultaneously
S
2
and
S
3
with a loss of 50%. If the quarter-wave plate is removed,
S
2
can be measured on both halves of the original beams.
