Communication without sending data

Using quantum effects to achieve the (im)possible

A long, but well-crafted, article in Scientific American, 27 June 2017, by Joshua Roebke explains the experimental history leading up to the point where “some physicists believe that we may be able to communicate without transmitting particles.”

Read the full article here

Indeed the latest experiment actually sent a black-and-white image of a Chinese knot, over the course of several hours, to a computer, without transmitting any particles or photons. “A monochrome bitmap appeared through static, although the group had not transmitted any particles.”

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The experimental apparatus showed that, “using a chained version of the Zeno effect, information can be directly exchanged between A and B with no physical particles travelling between them, thus achieving direct counterfactual communication.”

The actual apparatus consisted of many small interferometers, nested inside a large one, and this design can be iterative, to improve fidelity of communication.

Salih and his colleagues declare, “we strongly challenge the long-standing assumption that information transfer requires physical particles to travel between sender and receiver.”

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Causality questioned

Causal ambiguity is experimentally real

“Within the mathematical formalism of quantum theory, ambiguity about causation emerges in a perfectly logical and consistent way.”* This is an extraordinary statement made in an excellently written article by Philip Ball in the preeminent journal ‘Nature’, 28 June 2017.

Click here to read the article.

The article explores experiments which put photons through pairs of optical gates, and find that it is impossible to state in which order the photons go through the gates. “It’s not that this information gets lost or jumbled — it simply doesn’t exist. The experimental arrangement enables information to be shared between two events in ways that are ruled out if there is a definite causal order – So that time seems to run in two directions at once.”

This links in directly with the issues around distantly separated entangled photons cooperating instantly when the property of one is measured. It is probable that quantum circuits incorporating causal ambiguity would offer a practical benefit of greater quantum-computing speed. But more important is the potential for theoretical understanding of causality and the obscure nature of quantum effects.

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*I borrowed this extraordinary sentence as one of the chapter titles in my sci-fi novel.