Researchers successfully send first-ever quantum-encrypted message in real-world setting

In an ambitious bid to use quantum mechanics for encryption, researchers have taken a promising new step toward securing communications leveraging photons in their different quantum-states – this time, packing more than one bit of information per light particle.

Whereas scientists recently achieved quantum-encryption communications with one-bit-per-photon (in the form of a 1 or a 0 per each light particle), researchers at the University of Ottawa, Canada managed to pack two bits per photon (in the form of 01, 10, 00 or 11). They also managed to achieve successful data transfers in turbulent, real-world city conditions.

The high-dimensional encryption scheme is called 4D encryption – stemming from the four possibilities of 01, 10, 00 or 11 per photon.

Research team leader Ebrahim Karimi said the work is a world-first, in that secured messages could be sent using 4D quantum encryption in realistic conditions, not just in environments devoid of interference, like labs.

“Our work is the first to send messages in a secure manner using high-dimensional quantum encryption in realistic city conditions, including turbulence,” said Karimi. “The secure, free-space communication scheme we demonstrated could potentially link Earth with satellites, securely connect places where it is too expensive to install fiber, or be used for encrypted communication with a moving object, such as an airplane.”

The researchers set their sensitive optical gear atop two buildings 0.3 kilometers apart and covered them with wooden boxes to provide some protection from wind, dust and precipitation. As a final product would sport some form of housing for protection, we can safely say the team didn’t cheat much.

“After much trial and error, they successfully sent messages secured with 4D quantum encryption over their intracity link. The messages exhibited an error rate of 11 percent, below the 19 percent threshold needed to maintain a secure connection,” reads the report published by The Optical Society.

Furthermore, by comparing 4D encryption with 2D encryption (i.e. two bits per photon versus one bit per photon), researchers found they could transmit 1.6 times more information per photon, even with turbulence.

Traditional encryption – such as that advertised by messaging services Signal and WhatsApp – largely relies on mathematics. But computers are becoming so powerful that securing communications will soon require a more advanced approach, experts believe.

Quantum encryption promises to make communications much more secure in the future as it relies not on math, but on the changing quantum states of subatomic particles (such as electrons and photons).

In a similar effort earlier this year, researchers from the Max Planck Institute went so far as to prove that any attempt to hack quantum-encrypted communications was futile because of the infamous “observer effect” in quantum physics – where simply observing (or measuring) a system causes it to change.

Ottawa researchers plan to implement their findings into a much larger network that includes three nodes for their next test. They also plan to employ adaptive optics to further compensate for the turbulence and achieve more accurate results.

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