Particle of light teleported over six kilometres

In a first, scientists have successfully teleported a photon - particle of light - over a distance of six kilometres, an advance that may enable secure communication without having to worry about eavesdropping.
Researchers at the University of Calgary in Canada, led by professor Wolfgang Tittel, set a new record for distance of transferring a quantum state by teleportation, using fibre optics cable infrastructure.
"Such a network will enable secure communication without having to worry about eavesdropping, and allow distant quantum computers to connect," said Tittel.
The experiment is based on the entanglement property of quantum mechanics, also known as "spooky action at a distance" - a property so mysterious that not even German physicist Albert Einstein could come to terms with it.

"Being entangled means that the two photons that form an entangled pair have properties that are linked regardless of how far the two are separated," said Tittel.
"When one of the photons was sent over to City Hall, it remained entangled with the photon that stayed at the University of Calgary," he said.

Next, the photon whose state was teleported to the university was generated in a third location in Calgary and then also travelled to the City Hall where it met the photon that was part of the entangled pair.
"What happened is the instantaneous and disembodied transfer of the photon's quantum state onto the remaining photon of the entangled pair, which is the one that remained six kilometres away at the university," said Tittel.

One of the critical pieces of infrastructure that support quantum networking is dark fibre.
Dark fibre, so named because of its composition - a single optical cable with no electronics or network equipment on the alignment - does not interfere with quantum technology.
This demonstration is arguably one of the most striking manifestations of a puzzling prediction of quantum mechanics, but it also opens the path to building a future quantum internet.
The study was published in the journal Nature Photonics.