Stealth planes currently go under the radar, figuratively speaking, but maybe the higher definition promised by quantum radars could be used to expose them. Radar technology has become an ever more important tool in warfare since the Second World War, used to monitor the electromagnetic spectrum to detect and track enemy aircraft, missiles, satellites and other systems that in turn have grown more sophisticated in evading detection. Building better, more sensitive and harder-to-detect radar systems remains a key focus for defence manufacturers today, especially since in October 2018 the US Navy designated the electromagnetic spectrum as a warfighting domain on par with sea, land, air, space and cyber. Last year, China's biggest defence electronics company, state-owned China Electronics Technology Group, announced it had developed a next-generation quantum radar system' that, it claimed, can detect ballistic missiles and other objects flying at high speed through space. Two years previously, the group said it had tested a quantum radar to a range of 100km (60 miles). The expectation is that quantum radar, due to the unique behaviour of quantum entanglement, could, among other things, 'un-stealth' aircraft by detecting objects with a greater level of accuracy than conventional radar. Therefore, if China's announcement is true - and it hasn't provided any evidence to back its claim - it would be a huge win for both its defence and quantum capabilities.