The Weird World of Quantum Mechanics is Going Underwater

With the success of quantum satellite Micius in transmitting unbreakable codes through space, the world may also soon make use of seawater as a quantum channel as more scientific studies unravel the power of quantum physics.

Quantum Mechanics Going Underwater

Hack-proof digital communication has long been the desire and pursuit of countries and major financial institutions around the world. In fact, the scale of financial damage caused by the decryptors of personal and sensitive information has now reached more than $400 billion per year.

The solution to this problem experts have been looking into is quantum communication. By using a quantum channel in the transmission of entangled photons, the possibility of being hacked is reduced to zero.

This has been proven recently by Micius, a quantum-enabled satellite that China launched last year. China and Austria have been collaborating together in a project called Quantum Experiments at Space Scale (QUESS), whose objective is the development of quantum encryption and quantum teleportation technology.


The project succeeded in transmitting entangled photons from ground-to-space in its initial attempt, and scored a victory again in its space-to-ground transmission just weeks ago.

A photon is a particle of light, and it’s been very useful in quantum communication. Scientists produce entangled photons by beaming laser through a special crystal which splits a photon into a pair. This results to photons which remain connected even if they are separated by enormous distances.

Entangled photons are already used in digital communication via optic-fiber. But these land-based cables have their limitations. Secured transmission of entangled photons via optic fiber is possible only up to 200 kilometers. When repeater stations are used to boost the signals, the messages become open to hacking.

Hence, using space as a quantum channel became China and Austria’s goal. Through QUESS, they have proven that Micius could receive and send unbreakable codes at amazingly great distances.

But the system still needs to be perfected since conditions during transmission of the entangled photons had to be carefully observed in terms of ensuring cold temperature and absence of other sources of light.

QUESS is pushing on to conquer limits and succeed in its grand mission.

Now that the world have optic fiber and open space for quantum channels, will it be possible to use seawater for quantum communication as well?

Another group of Chinese researchers has just proven that this is viable.

Ling Ji and his colleagues at the Shanghai Jiao Tong University conducted a study to check the feasibility of seawater quantum channel. They collected seawater samples from the surface of coastal sea in a region between Dalian city and Zhangzi island. Then, they used a 3.3-meter-long glass tube with inlet and outlet and filled with different seawater samples including distilled water as a testbed of quantum channel.

After producing the entangled photons, the researchers separated them by placing them at the both ends of the tank. The team found out that the photons could communicate with more than 98 per cent accuracy.

“Our results confirm the feasibility of a seawater quantum channel, representing the first step towards underwater quantum communication,” the researchers stated in The Optical Society where their study was published.

While there are people in the field who have been impressed by the results, there are also those who remain skeptical by noting that there are important questions which need to be answered, like distance limitations for quantum underwater communications, and if the experiment could have the same effective results in open water. An objective observation given the experiment has been conducted only with seawater and in a tank.

Nonetheless, the world is optimistic that it can soon succeed in one of civilization’s oldest battles, that of producing 100 per cent secured communication and that the technological advancements may finally lead to quantum internet, the kind of network that protects data as it travels from point to point using quantum encryption.

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