Just recently scientists were able to demonstrate what Einstein famously described as “spooky action at a distance” or quantum entanglement – happening between macroscopic objects, a major step forward in our understanding of quantum physics.
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.”
“The next step is to demonstrate teleportation of the mechanical vibrations,” says Woolley. “In teleportation, the physical properties of an object can be transmitted using the channel of `spooky action’.”
Einstein himself described it as like two halves of the same coin, split up: if you have heads, the other half must be tails, even if it’s millions of light-years away.
“In quantum teleportation, properties of physical bodies can be transmitted across arbitrary distances using the channel of ‘spooky action at a distance’,” says one of the team, Caspar Ockeloen-Korppi from Aalto University in Finland.
“We are still pretty far from Star Trek, though.”
While it’s hard to say where this work will lead us next, it can’t be understated how important it is that we’ve taken this first step into macroscopic quantum mechanics.
“It is clear that the era of massive quantum machines has arrived,” Woolley explains in a piece for The Conversation. “And is here to stay.”
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.
The research has been published in Nature.