Physics

Why is Quantum Radar more Secure than Ordinary Radar



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Quantum radar technology is still in its development stage, and high claims are being made for it. One of its most promising applications is in a foolproof radar system, specifically in the field of detection and identification of enemy aircraft. Radar has been used from its earliest days in such a capacity, but has always been plagued by the problem of "jamming." This is where the enemy intercepts the radar signals and transmits back a deceptive one in order to disguise its presence. Quantum indeterminacy appears to be the key. The researchers have used this principle to produce a radar beam that is tagged with an unreadable code. If the code cannot be read, the beam that is transmitted back, despite being “cloaked” with the utmost sophistication, is easily detected as of enemy origin.

Radar technology was perfected in the heat of the Second World War, and played a decisive role in the victory of the Allies. During the Battle of Britain, when Hitler’s air force was swarming over the British Isles, the fate of the nation, and probably the free world, hung in the balance. In the end, it was the swift development of ground-based radar technology that saved the day for Britain.

The principal drawback to radar defense technology is its simplicity. Hitler's scientists were very quick to come up with a response - radar jamming. Knowing what to expect, the jammer intercepts radar signals, then transmits back something else, confusing the enemy with false parameters, or even disguising itself as an innocent target, probably a bird.

Radar works on the principle of bouncing electromagnetic waves off the target, and using the reflected beam to work out information regarding the target. The Doppler shift of the reflected beam gives the velocity of the target, while the elapsed time gives the distance. Modern radar technology uses microwaves instead of the original radio waves. This allows for higher definition in the reflected image, so that a map of the intensity is able to produce an image of the target, greatly aiding identification.

However, jammers are always able to keep up with the technology. Some motorists use highly sophisticated jammers to fool the speed guns carried by police. Researchers have long identified the problem to be that radar consists of open signal. This means that whatever is sent the way of the enemy can easily be detected and analyzed.

This is what the research team at the University of Rochester, New York, headed by Mehul Malik, have chosen to address. Quantum indeterminacy shows the way. They use a laser beam in which successive photons are polarised in one of two ways, according to a predefined code. Laser usually contains photons uniformly polarized, which is easily identified. Instead the researchers used a beam of mixed polarizations (using quantum entanglement).

The problem for the enemy occurs in trying to identify the particular polarization of an intercepted photon. Quantum indeterminacy shows that this cannot be done.  Supposing the polarization imparted by the transmitter is in either the horizontal or vertical direction. If the photon is intercepted, it has an equal chance of displaying either horizontal or vertical polarization regardless of its origin. Therefore, whatever jamming beam the enemy transmits back has a likelihood of containing 50 percent of the polarizations in the wrong direction. The reflected beam, on the other hand, retains its set of polarizations. Thus, the jamming beam is easily identified as unfriendly.

There remain a few obstacles before the researchers, though. Lasers work well in the laboratory setting. But in real life terrain, where large distances are involved, and various meteorological impediments are in the way, the reflected laser beam is likely to lose much of its polarized information.

However, by using a laser in the laboratory setting, the researchers have at least been able to demonstrate the principle at work. There remains much to accomplish. But the findings certainly show potential. If realized, radar working on the principle of quantum entangling would certainly be far more secure than its traditional counterpart.

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