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Scientists Achieve Direct Counterfactual Quantum Communication For The First Time (sciencealert.com)
schwit1 shares an article from ScienceAlert:
Quantum communication is a strange beast, but one of the weirdest proposed forms of it is called counterfactual communication -- a type of quantum communication where no particles travel between two recipients. Theoretical physicists have long proposed that such a form of communication would be possible, but now, for the first time, researchers have been able to experimentally achieve it -- transferring a black and white bitmap image from one location to another without sending any physical particles... It works based on the fact that, in the quantum world, all light particles can be fully described by wave functions, rather than as particles. So by embedding messages in light the researchers were able to transmit this message without ever directly sending a particle.
It's different than quantum entanglement (which Einstein described as "spooky action at a distance.") The article describes it as "a pretty cool demonstration of just how bizarre and unexplored the quantum world is."
It's different than quantum entanglement (which Einstein described as "spooky action at a distance.") The article describes it as "a pretty cool demonstration of just how bizarre and unexplored the quantum world is."
"How is this different than radio?"
Signal strength. If implemented in the real world it would be harder to jam or disrupt. We already have used tight beam laser communications but they are line of sight and susceptible to interference by any particles between the source and target. It seems this new attempt at something else would provide better performance without the line of sight or environmental obstructions getting in the way. If any of this type of technology becomes practical look for it to show up in the military technology basket. This new technology also opens the door for advancements in encryption making interception and deciphering the content much more difficult if not impossible at this time.
Radio waves are photons too. Light is just photons that happen to have the right frequency for our eyes to pick up. Whenever electrons are changing magnetic fields that act on other electrons, deep down at the quantum mechanical level it turns out to actually be an interchange of photons.
In this latest experiment, no photons or any other kind of particles were exchanged between emitter and receiver. So it really is quite different.
In this latest experiment, no photons or any other kind of particles were exchanged between emitter and receiver. So it really is quite different.
That's not actually quite true. Photons are sent (and in fact photon counters are used to detect the signal). However, the information itself isn't encoded in the photons, it's encoded in the phase of the photons. The abstract uses the comparison to holography: in normal photography, only the amplitude of the light is relevant. In holography, the phase of a laser is used to encode information as well (specifically, the 3D depth of the target) in addition to the amplitude. This technique encodes all of the information into the phase alone, and none of it stays in the amplitude.
TFA is, to put in bluntly, wrong. It claims
It works based on the fact that, in the quantum world, all light particles can be fully described by wave functions, rather than as particles. So by embedding messages in light the researchers were able to transmit this message without ever directly sending a particle.
But light is photons, and photons are light. You can't encode information in light without sending photons: it's like saying you talk to someone over the phone using words, but without using sound. It's just absurd. Of course, you can communicate over the phone using sound without using words, which is roughly analogous to what the scientists actually did.
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
Yes, and every single detected photon in the universe is a counterfactual to all the other paths the photon could have taken. Normally, these paths are numerous and unknowable, but if you build a machine just right, you can restrict the paths so much that there are just a few, and witnessing one path can eliminate some others as possibilities, and also prove the existence of a separate but coherent path.
Although restricting the paths is one way to do this (with the quantum bomb detector), I believe the proposed quantum counterfactual communicaton technique actually uses the Quantum Zeno Effect. Instead of restricting the paths of a photon, the Quantum Zeno effect restricts the time-evolution of the photon temporarily preventing quantum decoherence.
Basically a watched pot never boils on (quantum) steroids.
This Quantum Zeno effect has also been proposed as the mechanism for long spin coherence lifetimes of radical-ion pairs that birds likely use for Magnetoreception