A collaboration between the City of Calgary, the University of Calgary and U.S. researchers may have brought quantum internet closer to reality.
Physicists led by Wolfgang Tittel, professor in the Department of Physics and Astronomy at the University of Calgary have successfully carried out the teleportation of a photon over a distance of six kilometers. The teleportation was made using the city of Calgary’s fiber optic cable system, and the full findings of the research were published in the journal Nature Photonics.
Photon teleportation raises hopes for quantum internet
The researchers broke the record for the distance of transferring a quantum sate by teleportation.
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“Such a network will enable secure communication without having to worry about eavesdropping, and allow distant quantum computers to connect,” says Tittel.
The researchers worked with an entanglement property of quantum mechanics, known as “spooky action at a distance.” This property was known to have baffled Albert Einstein.
“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,” explains 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.”
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Researchers were able to make the teleported photon generate in a third location. It then traveled to City Hall and met up with its fellow entangled proton.
“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,” says Tittel.
The research was made possible due to the accessible dark fiber network built by the city of Calgary. Dark fiber doesn’t interfere with quantum technology, and the city has been proactive in using it for next-generation municipal services.
“By opening The City’s dark fibre infrastructure to the private and public sector, non-profit companies, and academia, we help enable the development of projects like quantum encryption and create opportunities for further research, innovation and economic growth in Calgary,” said Tyler Andruschak, project manager with Innovation and Collaboration at The City of Calgary.
Researchers excited by step towards quantum internet
One challenge for the researchers was that the transmission time varied with changes in the outdoor temperature. This meant that two photons would meet at City Hall at one temperature, but not later in the day when the temperature had changed.
“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.”
The work has been hailed as an important piece of evidence of one of the most puzzling parts of quantum mechanics. It also raises the possibility of a quantum internet being built in the future. Tittel and his team will continue to work towards that goal.
A quantum internet would work to improve security of data transmission. This is because, in quantum mechanics, observing the quantum state of a particle also changes its quantum state. This means that it would be impossible to intercept a communication without the receiver being aware of the interception.
“If you encode keys into quantum states and send them from person to another — for instance, through teleportation — then it turns out that you can verify at the receiver’s side … if an eavesdropper has acquired any information about that key,” Tittel said. “If you find out that nobody has tampered with this transmission, you know that you share a perfectly secure key and then you can use it to encrypt some sensitive data.”