Cryptography Reference
In-Depth Information
Bell measurement, the second trunk between the Bell measurement and the
EPR source and the last one from there to Bob's receiver (see Figure 2.12). Fi-
nally, let us mention an experimental realization of entanglement swapping
[70], where photons more than two kilometers apart are entangled, although
they never interacted directly. We use two pairs of time-bin entangled qubits
created in spatially separated sources and carried by photons at telecommu-
nication wavelengths. A partial Bell state measurement is performed with
one photon from each pair, which projects the two remaining photons, for-
merly independent, onto an entangled state (see Figure 2.13). The visibility
Bob
Alice
F
M
F
M
Charlie
BSM
β
α
Ge
InGaAs
FM
F
M
C
1
C
2
InGaAs
Beam splitter 50:50
InGaAs
1550 nm
1550 nm
1310 nm
1310 nm
B
C
D
A
1.1 km DSF
1.1 km DSF
WDM
WDM
SF
SF
LBO
LBO
Pump
interferometer
δ
Femto-second laser
λp = 710 nm
Figure 2.13
Experimental setup for entanglement swapping. The pump laser is a
mode-locked femtosecond Ti-sapphire laser producing 200 fs pulses at a wavelength
of 710 nm with a repetition rate of 75 MHz. After the crystals, the pump beams are
blocked with silicon filters (SF). The Faraday mirrors (FM) are used to compensate
polarization fluctuations in the fiber interferometers.
