China & the World’s Most Sensitive Submarine Detector … Almost!

“COULD China soon have the world’s most sensitive submarine detector? On 21 June, the Chinese Academy of Sciences hailed a breakthrough – a major upgrade to a kind of quantum device that measures magnetic fields. Then the announcement vanished, after a Hong Kong newspaper pointed out the potential military implications: the invention could help China lock down the South China Sea.

Magnetometers have been used to detect submarines since the second world war. They do this by measuring an anomaly in Earth’s magnetic field – like one caused by a giant hunk of metal.

But today’s devices can only detect a submarine at short range.You could extend this if you had a magnetometer based on a superconducting quantum interference device, or SQUID. These are highly sensitive, but they
are also quickly overwhelmed by background noise.

The new device, built by Xiaoming Xie and colleagues at the Shanghai Institute of Microsystem and Information Technology, uses an array of SQUIDs. The idea is that by comparing their readings, researchers can cancel out some forms of error due to motion – for example, when SQUIDs are put on aircraft.

David Caplin at Imperial College London, who works on magnetic sensors, says this“would be relevant to an anti-submarine warfare device”. The breakthrough points to an airborne system that can detect submarines from several kilometres away rather than just a few hundred metres.

SQUIDs are only one of the ways China has been upgrading its anti-submarine capability over the past few years. The “Underwater Great Wall”, a string of submerged sensors, buoys and drone submarines, is thought to be close to completion. The project will help China extend its offshore surveillance zone.” (Hambling, 2017, p.9).


Hambing, D. (2017) New Submarine Detector for Contested Seas. New Scientist. 26 August 2017.


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