Quantum communication is a hard concept to grasp, but to make things even more complex, researchers have just achieved counterfactual communication—a type of communication where no particles travel between the two recipients.
Counterfactual communication has been proposed by theoretical physicists for some time, but this is the first time researchers have been able to prove it experimentally by transferring a black and white bitmap images from one location to another.
As mind-bending as that sounds, counterfactual quantum communication is actually quite intuitive to grasp once you understand how it differs from regular quantum teleportation. Regular quantum teleportation is built on the principle of entanglement, or the idea that two particles become inextricably linked, meaning whatever happens to one will automatically affect the other. Einstein described this relationship as “spooky action at a distance.”
Regular quantum teleportation relies on particle transmission because the particles need to be together when they’re entangled before being sent to the people on either end of the message. Particles cannot be entangled at a distance without the help of another particle traveling between the two.
Counterfactual quantum communication relies on the quantum Zeno effect rather than quantum entanglement. According to science alert: “Very simply, the quantum Zeno effect occurs when an unstable quantum system is repeatedly measured. In the quantum world, whenever you look at a system or measure it, the system changes. And in this case, unstable particles can never decay when they’re being measured…”
To accomplish counterfactual quantum communication, a quantum channel must run between two sites, introducing the small probability that a quantum particle will cross the channel.
The results of the recent experiment will need to be verified by external researchers, but this is a big step forward for quantum communication.