Russian scientists unveil quantum communication device

ST. PETERSBURG, Russia, April 13 (UPI) -- Researchers with ITMO University Russia say they've created a long-distance quantum communication device that theoretically can't be hacked.

The device embeds information in a single photon, which is sent across optical fibers stretching up to 155 miles long. Should hackers attempt to intercept and spy on the photon, it will be irreversibly altered.

The research team at ITMO developed the technology with the help of scientists from Heriot-Watt University in Edinburgh in Scotland.

Encoded information is sent via a laser beam that passes through an electro-optical phase modulator. The modulator splits the beam into different wavelengths. A modulator on the other end of the cable splits the photon beam once more.

Depending on the phase shifts of the individual wavelengths, the waves either enhance or cancel each other. Overlapping wavelengths are translated into binary digits of 1 and 0. The combination of digits form a quantum key securing the embedded information. The researchers say their system has shown high stability.

"All waves undergo random changes while passing through the fiber," Oleg Bannik, a researcher at ITMO's Quantum Information Centre, said in a press release. "But these changes are always identical and get smoothed over during the additional run through the receiver's modulator. In the end, the receiver observes the same combination as the sender."

Researchers say their new device, the first in Russia, has a bitrate and distance on par with the most advanced analogues.

"To transmit quantum signals, we use the so-called side frequencies," explained Artur Gleim, head of the Quantum Information Centre. "This unique approach gives us a number of advantages, such as considerable simplification of the device architecture and large pass-through capacity of the quantum channel. In terms of bitrate and operating distance our system is comparable to absolute champions in the field of quantum communications."

To steal or spy on a quantum key, a third party must measure it, but doing so introduces anomalies that the two communicating parties can detect. For this reason, scientists consider quantum communications essentially "unhackable."

Researchers described the new device this week in the Optics Express journal. They believe the new technology can be used to protect all kinds of information.

"Down the track, this new approach can enable smooth coexistence of numerous data streams with different wavelengths in one single optical cable," study co-auhtor Robert Collins, a quantum scientist at Heriot-Watt University, told Russian news agency TASS. "On top of it, these quantum streams can be fed into the already existing fiber optic lines along with conventional communications."