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Just when you thought things could not get cooler or weirder... A pulse of light can have almost any shape in space and in time, determined by the amplitudes and phases of its frequency components. Surprisingly, single photons can also be generated in a variety of complex shapes. The difference is that the amplitude for a single photon doesn’t represent a definite value of the electric field strength; instead it’s associated with the probability of detecting the photon at each location and time.
Researchers could also encode information in the photon shape and transmit it from one place to another. There is so much flexibility that a single photon could represent any letter in the alphabet, for example, or even a quantum combination (superposition) of several letters. ... They created photons that had two separate frequency components with a particular phase difference. These photons were efficiently detected using local oscillator pulses that had a matching phase difference.
http://physics.aps.org/articles/v5/86
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7 comments
 
Am I interpreting this correctly? Is this a backdoor approach to quantum-style computing without the de-coherence problem? 
 
Crossing the streams bit, but take this in light (pun intended) of the previous question about detecting alien cultures: one of the classic answers to this question has always been, "we don't know how to detect the kinds of communications that alien civilizations would put out." Imagine, if you will, two continents that can be seen on each other's horizons, one teaming with aboriginal cultures, all of which have stone-age level technology, the other populated with modern cultures that, for whatever reason, choose not to disturb the natives of the other landmass. The lower-tech peoples find themselves convinced that there are no other civilizations outside of their area because when they look across the sea, they don't see any of the types of "light signatures" that they would expect. No smoke signals; no kites; no mountaintop bonfires.

Of course, we're in the same boat. Though we don't know if there are alien civilizations or not, we certainly would not be likely to be able to detect them. We expect to see batches of photons sent in pulses of modulated amplitude or frequency, but what if the information was encoded on photons or "cosmic rays" (which is to say, near-speed-of-light particles)? Would there be any detectable signal to us, or would we just see a sea of undifferentiated "noise", unaware of how to read the content, and thus left to assume that we're looking at the result of natural proceses?
 
So it is similar to the propagation of an EMF wave envelope ?

How many pulses are in a wave envelope and how many photons are in a ray? +David Brin 
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