Posted on December 5, 2018
Before the Second World War, the only way to detect incoming aircraft was the Mk 1 Eyeball, useless in the dark or bad weather, or with short-range listening apparatus. Radar changed the situation dramatically. Things are set to change again with the new technology of quantum radar. Radar works something like a searchlight. The radar scans the sky with a beam of radio waves, and any reflections – say, from, an aircraft – return to the dish where they are detected. Radar was the secret weapon that helped win the Battle of Britain, spotting formations of Luftwaffe aircraft at long range in the dark, so fighter squadrons could be dispatched to intercept them.
Ever since then, a large part of air warfare has been devoted to avoiding or neutralising radar. In the post-war period, bombers started flying close to the ground, hiding behind the terrain and staying under the coverage of radar. This is why RAF jets may be found hugging valley floors in designated ‘low flying areas’ in sparsely populated areas.
However, flying low is less use against modern opponents with airborne radar. Other means of dealing with radar were developed, including electronic jamming – broadcasting radio noise on the same frequency as the radar to blank out the returns from the aircraft – and electronic spoofing – sending signals which create fake radar returns from non-existent aircraft. Some modern aircraft like the F-35 also have stealth: a combination of shaping and materials to make their radar reflection so small it gets lost in the background noise. Finally, attackers may simply bomb the radar sites, which are easy to spot from their powerful radio emissions. This combination of measures allows combat operations over defended territory, but that may change with the introduction of quantum radar.
A quantum radar produces two radio beams, which are connected by so-called “quantum entanglement”. This is a peculiar effect in which two photons in different beams can be connected with each other, even though they are miles apart. It is a weird effect; even Einstein was doubtful about whether quantum entanglement was possible, calling it “spooky action at a distance,” but since then it has been proven to work.
One beam is sent out, just like a standard radar beam, and bounces back off objects in the sky. The second, ‘idler’ beam, remains inside the system. Any reflections which come back can be matched with those in the idler beam. Entanglement means that any stray radio waves, or those that came from any other sources, such as spoofing or jamming, can be filtered out. Background noise is also eliminated, so even the faint reflections from a stealth aircraft can be spotted relatively easily. This means quantum radar can, in theory, beat current methods of countering radar. An added benefit is that, because of their low power levels, quantum radar is difficult to detect, making it less vulnerable to enemy action.