Quantum-entanglement record could mean hack-proof communications

By Jean-Jacques DeLisle, contributing writer

When Einstein was struggling with quantum weirdness concepts such as spooky action from a distance, it was unlikely that he could have predicted that this quirk of quantum physics could eventually be used to send data over a thousand kilometers, virtually instantly, and with built-in hacking protection. Essentially, quantum-entanglement is the phenomenon that enables two particles to have intrinsically opposite spins. When one of these particles is observed, the spin of the paired particle is always opposite, regardless of the distance of separation.

Image source: Morguefile.

As the spin of a particle can be either up or down, it naturally allows for binary data transmission. However, the energy loss of terrestrial transmission of entangled particles has been a limiting factor in the distance that paired photons have been able to be transmitted. Signals are attenuated and weakened when transmitted through optical fibers or the atmosphere, and the sensing equipment used to capture the quantum-entangled photons has a limited sensitivity. Hence, prior attempts at long-distance quantum communication were limited to around 100 kilometers.

For a visual description of quantum-entanglement, check out the video below.

But the story doesn’t end there. The record for the longest distance that quantum-entangled particles has communicated was just broken by a research group from the University of Science and Technology of China, who has been working on the satellite-based quantum-entanglement communication system since 2003. Using China’s Miscius satellite equipped with an ultra-bright entangled photon source and high-precision acquiring, pointing, and tracking (APT) system, the team was able to transmit beams of entangled photons to two different locations on Earth between 1,600 and 2,400 kilometers, depending upon orbit.

“Many people then thought it [was] a crazy idea because it was very challenging already doing the sophisticated quantum-optics experiments inside a well-shielded optical table,” Pan Jianwei, a professor of quantum physics at the University of Science and Technology of China, told Live Science. “So how can you do similar experiments at thousand-kilometer distance scale and with the optical elements vibrating and moving at a speed of 8 kilometers per second [5 miles per second]?”

Beaming the entangled photon pairs from a satellite allows the particles to travel through lossless free space for the majority of the distance, reducing the signal loss to the last portion of the trip through the atmosphere. Still, only roughly one in 6 million of the transmitted photons were recovered.

“We have already achieved a two-photon entanglement distribution efficiency a trillion times more efficient than using the best telecommunication fibers,” said Pan. “We have done something that was absolutely impossible without the satellite.”

Though also very exciting to quantum physicists, this technology also has potentially revolutionary applications. One such application was proposed by Artur Ekert, a professor of quantum physics at the University of Oxford in the United Kingdom. While still a student at Oxford, Artur proposed the use of quantum entanglement as a means of sending communication encryption keys. The benefit of using quantum communication is that if any party intercepted entangled pairs from a communication, the third party could only observe the particles by disturbing them and alerting the communicating parties.

With other Quantum Experiments at Space Scale (QUESS), or Micius satellites, in orbit, quantum communication technologies could be used to ensure the protection of sensitive information and enable faster-than-light communication between two points on Earth. Due to the costs and specialized scientific equipment needed to receive and measure the entangled particles spin states, it’s likely that this technology will stay in the realm of quantum physics experimentation for quite some time. Future applications for ultra-secure banking and governmental/military sensitive information exchange may arise. Another far-distant application could be interplanetary and intergalactic communication that doesn’t suffer from the lag time associated with light-speed communication.