Transferring information from one place to another without transferring particles or energy seems to contradict everything we’ve learned in the history of physics.
Still, there is some evidence that this “counterfactual communication” might not only be plausible but, depending on how it works, could also reveal fundamental aspects of reality that have so far remained hidden.
Counterfactual physics is nothing new per se and describes a way of deriving activity from the absence of something. In a way, it’s pretty straight forward. If your dog barks at strangers and you hear silence when the front door opens, you have received information that a familiar person has entered your home, although there is no sound.
But that’s where the question of a quantum version of this form of transmission has been surfacing in recent years, with physicists exploring the possibility of transporting quantum information without exchanging a particle.
The concept is not just theoretical. Ghost imaging uses a separate pair of entangled photons to derive information about an object without it absorbing and transmitting any of the particles.
A leading researcher in the field has proposed an experimental design to test the physics behind a type of exchangeless communication, a method he calls counterportation.
As you might expect given the nature of the physics involved, quantum computing plays a part. The proposal uses qubits — the probability-based versions of classic binary information carriers — to carry information from one place to another without ever interacting.
Salih’s previous research involves light being separated by complex arrays of splitters and detectors, showing an unintuitive result of information arriving at a destination even though there’s no particle to carry it.
What the physicist is proposing is a new computational scheme based on his earlier theoretical protocol Released in 2013.
“Remarkably, while counterportation achieves the ultimate goal of teleportation, which is disembodied transport, it does so with no detectable information carriers traveling across,” says physicist Hatim Salih of the University of Bristol in the UK.
“If counterportation is to be realized, a whole new type of quantum computer has to be built: an exchange-free one, in which communicating parties do not exchange particles.”
Teleportation is an established means of transferring a quantum state from one place to another. Although the details are complex, multiple objects must be entangled and then separated at an arbitrary distance before the entangled objects can be carefully measured at one location in a very specific way. The act of teleportation is only realized when the separated object is also measured against the findings transmitted in the old-fashioned way.
The end result is not the transmission of a solid object as such, but rather a very specific quantum state. Completing the measurements on the original object effectively destroys it, meaning this state has effectively jumped from one place to another.
Counterportation is a quantum form of counterfactual communication that results in the transmission of quantum information, similar to teleportation (only without the extra hassle).
The obvious question is how. This is where a certain type of Einstein-Rosen (ER) bridge or wormhole comes into play, which is thought to represent the overlap or connection between entangled objects.
According to Salih, such a local wormhole could serve as the medium through which the counterportation takes place.
While wormholes have been theorized in terms of black holes, it is possible that they describe entangled phenomena on smaller scales as well. If wormholes do exist, describing them could help fill in gaps in our knowledge of the fundamental nature of matter.
“The goal in the near future is to physically build such a wormhole in the lab, which can then be used as a testbed for competing physical theories, even those on quantum gravity,” says Salih.
“Our hope is to eventually allow physicists, amateur physicists and enthusiasts remote access to local wormholes to study fundamental questions about the universe, including the existence of higher dimensions.”
We should note that this is all theoretical for now – and based on foundations that not all scientists agree – but it adds another intriguing layer to the scientific discussion going on about counterfactual quantum communication and its potential role in research.
“This is a milestone we have been working toward for a number of years,” says Salih. “It provides a theoretical and practical framework to re-explore enduring mysteries about the universe, such as the true nature of space-time.”
The research was published in Quantum Science and Technology.