Laying one of the first steps towards a future quantum internet where eavesdropping would be non-existent, a team of researchers from Canada and US have managed to teleport a photon over a straight-line distance of six kilometres.
The feat was achieved by a team of physicists led by Wolfgang Tittel, professor in the Department of Physics and Astronomy at the University of Calgary. Tittel’s ultimate goal is to a quantum internet that is not only blazing fast, but is also completely secure and to achieve that one of the primary requirements is to transport particles of light from one place to the other. Light-based communications have already been achieved through fibre-optics, but that’s not what the quantum scientists are after. They are looking for ways to teleport photons and not transmitting them. That’s where the Tittel group has achieved a major breakthrough.
Those interested in physics and advanced communications systems would have come across Einstein’s ‘spooky action at a distance’. If you haven’t, then it would suffice to state that it is to do with entanglement property of quantum mechanics [Refer Wikipedia here]. The property of photons is so mysterious that even Einstein had a hard time coming to terms with it.
In the words of Tittel, if a pair of photons are entangled it means that the two particles of light have properties that are linked regardless no matter the distance between them. For the experiment, the physicists sent one of the photons over to City Hall while it remained entangled with the photon that stayed at the University of Calgary. Then, the photon whose state was teleported to the university was generated in a third location in Calgary and then also travelled to City Hall where it met the photon that was part of the entangled pair. Tittel explains that what they observed was an “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.
The team had to overcome quite a few challenges to get to the end result. First of all they needed dark fibre – a single optical cable with no electronics or network equipment on the alignment — doesn’t interfere with quantum technology. The City of Calgary helped them out here. Then it was the outdoor temperature that caused a variation in the arrival times of the photon.
“The challenge was to keep the photons’ arrival time synchronized to within 10 pico-seconds,” says Tittel. “That is one trillionth, or one millionth of one millionth of a second.”
Another issue was to get hold of very specific pieces of equipment that would make the quantum experiment a reality – state-of-the-art superconducting single-photon detectors, compact cryostat, and others.
This accomplishment, which set a new record for distance of transferring a quantum state by teleportation, has landed the researchers a spot in the prestigious Nature Photonics scientific journal.