Star Trek Getting Closer.
In two studies published in Nature Photonics, separate research groups have used quantum teleportation to send photons to new locations using fibre-optic communications networks in the cities of Hefei in China and Calgary in Canada.
Quantum teleportation is the ability to transfer information such as the properties or the quantum state of an atom — its energy, spin, motion, magnetic field and other physical properties — to another location without travelling in the space between.
While it was first demonstrated in 1997, today’s studies are the first to show the process is technologically possible via a mainstream communications network.
The development could lead to future city-scale quantum technologies and communications networks, such as a quantum internet and improved security of internet-based information.
Dr Ben Buchler, Associate Professor with the Centre for Quantum Computation and Communication Technology at the Australian National University, said the technical achievement of completing the experiments in a “non-ideal environment” was “pretty profound”.
“People have known how to do this experiment since the early 2000s, but until these papers it hasn’t been performed in fibre communication networks, in situ, in cities,” said Dr Buchler, who was not involved in the research.
“It’s seriously difficult to do what they have done.”
A cornerstone of quantum teleportation is quantum entanglement, where two particles are intimately linked to each other in such a way that a change in one will affect the other.
Dr Buchler said quantum teleportation involved mixing a photon with one branch of the entanglement and this joint element was then measured. The other branch of the entanglement was sent to the receiving party or new location.
This original ‘joint’ measurement is sent to the receiver, who can then use that information to manipulate the other branch of the entanglement.
“The thing that pops out is the original photon, in a sense it has indistinguishable characteristics from the one you put in,” Dr Buchler said.
He said both teams had successfully overcome technical barriers to ensure the precise timing of photon arrival and accurate polarisation within the fibres.
The Chinese team teleported single protons using the standard telecommunications wavelength across a distance of seven kilometres, whiled the Canadian team teleported single photons up to 6.2 kilometres.
But work remained to increase the speed of the system with the Chinese group teleporting just two photons per hour and the Canadians a faster rate of 17 photons per minute.
Dr Buchler said the speeds meant the development had little immediate practical value, but “this kind of teleportation is part of the protocol people imagine will be able to extend the range of quantum key distribution” — a technique used to send secure encrypted messages.
In the future scientists envision the evolution of a quantum internet that would allow the communication of quantum information between quantum computers.
Quantum computers on their own would allow fast computation, but networked quantum computers would be more powerful still.
Dr Buchler said today’s studies were a foundation stone toward that vision as it showed it was possible to move quantum information from one location to another within mainstream networks without destroying it.