For the first time, researchers have demonstrated the precise requirements for secure quantum teleportation – and it involves a phenomenon known 'quantum steering', first proposed by Albert Einstein and Erwin Schrödinger.
Before you get too excited, no, this doesn't mean we can now teleport humans like they do on Star Trek (sorry). Instead, this research will allow people to use quantum entanglement to send information across large distances without anyone else being able to eavesdrop. Which is almost as cool, because this is how we'll form the un-hackable communication networks of the future.
Quantum teleportation isn't new in itself. Researchers have already had a lot of success quantum teleporting information over 100 km of fibre. But there's a slight issue – the quantum message was getting to the other end kinda incoherent, and scientists haven't exactly known what to do to prevent that from happening, until now.
"Teleportation works like a sophisticated fax machine, where a quantum state is transported from one location to another," said one of the researchers, Margaret Reid, from Swinburne University of Technology in Australia.
"Let's say 'Alice' begins the process by performing operations on the quantum state – something that encodes the state of a system – at her station. Based on the outcomes of her operations, she communicates (by telephone or public Internet) to 'Bob' at a distant location, who is then able to create a replica of the quantum state," she explains.
"The problem is that unless special requirements are satisfied, quantum mechanics demands that the state at Bob's end will be 'fuzzed up'."
The researchers have now shown that to avoid this, Alice and Bob (or anyone else who wants to send an entangled message) need to use a special form of quantum entanglement known as 'Einstein-Podolsky-Rosen steering'.
"Only then can the quality of the transported state be perfect," said Reid. "The beauty is that quantum mechanics guarantees that a perfect state can only be transported to one receiver. Any second 'eavesdropper' will get a fuzzy version."
Basically, in this quantum steering state, the measurement of one entangled particle can have an immediate 'steering' effect on the state of another distant particle.
The researchers will continue to investigate this phenomenon to figure out how it can be used to more reliably communicate using quantum entanglement.
This research has been published in Physical Review Letters.