Cryptography Reference
In-Depth Information
Bob
Switch
Alice
Anna
Boris
Figure 4.1
The metro-fiber portions of the DARPA Quantum Network.
Harvard-BBN strand is approximately 10 km. The BU-BBN strand is approx-
imately 19 km. Thus the Harvard-BU path, through the switch at BBN, is
approximately 29 km. All strands are standard SMF-28 telecommunications
fiber. Figure 4.2 presents the network in schematic form.
Anna's mean photon number is 0.5 at present, with the Anna-Bob link
delivering about 1,000 privacy-amplified secret bits/second at an average 3%
quantum bit error rate (QBER). At present, the DARPA Quantum Network
cannot support fractional mean photon numbers to Boris at BU, owing to
high attenuation in fiber segments across the Boston University campus and
relatively inefficient detectors in Boris. (BBN-BU attenuation is approximately
11.5 dB). Thus the network currently operates at a mean photon number of 1.0
Bob
Al
ex
Al
i
Alic
e
2 x 2
Optical
Switch
Anna
Boris
Barb
Ba
ba
@ Harvard
@ BU
Figure 4.2
Connectivity schematic of the DARPA Quantum Network.
