Cryptography Reference
In-Depth Information
Theory
Experiment
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Figure 6.10
First experimental demonstration of a CNOT gate for single photons.
(Reprinted with permission from T.B. Pittman, M.J. Fitch, B.C. Jacobs, and J.D. Franson,
Phys. Rev. A, 68, 032316, 2003. Copyright 2003 by the American Physical Society.)
It is also possible to construct a quantum memory for photons by switch-
ing them into an optical storage loop and then switching them out again when
needed [3,4]. In this case the system must maintain the polarization state of the
photons in order to preserve the value of the qubit, which is more challeng-
ing than the single-photon source described above. This can be accomplished
∆
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storage
loop
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PDC
detector
Figure 6.11
Implementation of a single-photon source using pulsed parametric
down-conversion (PDC). The detection of one member of a pair of down-converted
photons indicates the presence of the second member of the pair, which is then
switched into an optical storage loop until it is needed. (Reprinted with permission
from T.B. Pittman, B.C. Jacobs, and J D. Franson, Phys. Rev. A, 66, 042303, 2002. Copy-
right 2002 by the American Physical Society.)
