AAWSAP DIRD, The Space Communication Implications of Quantum Entanglement and Nonlocality, March 2010

Text

This text came with the file. It may have mistakes. When the text and the image disagree, the image is right.

UNCLASSIFIED//P81t errl@IAL ~SI! 8HL'I
VIII. Superluminal and Retrocausal Nonlocal
Communication
As mentioned in the previous section, we will assume for the sake of discussion that
nonlocal signaling is possible and will consider its implications for the speed of
transmission of signals. For definiteness, schemes for doing this are based on the slit­
imaging coincidence-free version of the Ghost Interference experiment described above
and shown in Figure 7. In that system, the instant at which a nonlocal signal is sent is
the arrival of the VLP photon at the fiber-optic system on the left, and the instant at
which the signal is received is the arrival of the HLP photon at the camera at the
bottom of the diagram. Assuming the workability of this scheme, both the instants of
sending and of receiving can be delayed, in principle, by the introduction of delay
paths-for example, runs of fiber-optic cables-in the system.
In particular, the "send" instant could be made to occur well after the "receive" instant
in the system, constituting a direct demonstration of retrocausal signaling. This is
shown in Figure 10. Here the cleanup two-slit system S2 becomes the entrance for two
10-km-long runs of fiber-optics that are carefully matched to have identical exit phases
at SJ, the end of the fiber runs where the light enters the optical switching arrangement
described above. If the index of refraction of the fiber is 1.5, light transiting the 10-km
path requires about 50 µs. In the presence of detection noise or the degradation of
pattern visibility because of compromises between entanglement and coherence,
considerably more photon detection events-say 100-might be required.
10km
Apertures
10km
Image Slits
Path lo Lens =f
IR Pass
Filler
HIJ>
702 nm
0!¥ctSlits
BBO
VLP
JSI nm
Path to Lens= f
S1
Camera
u 1 n
[/SJ
Figure 10. Slit-Imaging Coincidence-Free Version of the Ghost Interference Experiment Demonstrating
Superluminal and Retrocausal Signaling
UNCLASSIFIED//FOlil OFFI&il.t.k W&lii 8Nk¥
17