An extension of the quantum communications landline connecting East China’s Anhui province and central Hubei province is now up and running. The project is the latest in a slew of its kind as China expands a quantum communications network that is reportedly impossible to crack.

The new, 609-kilometer line connects the two provincial capitals, Hefei and Wuhan. It was built by the state-owned China Aerospace Science and Industry Corp, which develops and produces missiles and carrier rockets and also invests heavily in laser research and development as the base technologies for quantum communications.

The new line is now connected to the existing Beijing-Shanghai line that was inaugurated in September 2017.

China is devoting billions to the cutting edge network linking key cities. Governmental organs and vital agencies, from the military to research institutes, are being enticed by its ultra-high security. Information sent through the quantum network is almost impossible to be tapped, intercepted or cracked.

The Global Times noted that the network could help transmit classified information to a command center of the People’s Liberation Army, which could in return instantly instruct a combat unit during wartime.

The nation’s quantum communications ground network is connected to the world’s first quantum satellite, the Mozi (aka Micius), launched by China in August 2016.

Data encryption based on quantum computing, or quantum mechanics, was pioneered by the Los Alamos National Laboratory in the US, which announced in 2014 that it had created a secure network. Other nations including Germany, Japan, Australia and Sweden are known to be working on similar projects.

Traditional cryptographic systems use the factors of a number that is itself the product of two very large prime numbers to encode signals. This is done on the premise that it would take too much time, and too much computer processing power, for an algorithm to crack the system.

Quantum computing takes a more minimalist approach by limiting data communication to just two parties, the sender and one receiver. Entangled photons, or visible light particles, are sent to the two stations encoded with specific polarizations (the direction of the light wave’s wobble) as a security layer.

The satellite creates security keys using measurements of polarizations, which the stations can use to encrypt and decrypt the data. It is technically “unhackable”, as users can quickly detect the presence of a third party: anyone eavesdropping would be unable to look at the photons without changing or even destroying them.

“The laws of quantum mechanics make it physically impossible for the (transmission) to be intercepted and read without eavesdropping being detected by the sender and receiver,” an expert told the Beijing-based tabloid Global Times.

Such a secure system for transmitting encrypted voice calls, faxes and emails containing classified information would be of immense value for the top brass of the People’s Liberation Army and intelligence networks at a time when cyber warfare is taking on ever-greater importance.