I have often been reminded that my claim that I no longer race cars is not terribly accurate.  Oh, it’s true that I don’t have a race car, that I don’t compete on the track, but…to say I have a lead foot would be a grand understatement.

Decades ago, when I traveled between Charlottesville and Dulles or National airports (thrice weekly, at a minimum), I owned (and used) a radar tracking device.  I also had a confounding device.  Which insured one of two reactions- how did I just pass that police car and not be noticed on their radar (which often led to a chase…) or why did their radar gun cease operating (which meant a verification test would ensue).   I have not used such devices in a very long time.   And, now they may become moot, for those of you who do.

Drs. Mehul Malik, Omar Magaña-Loaiza, and Robert Boyd have just described their research in Applied Physics Letters.  While the title (Quantum Secured Imaging) may not divulge its secrets to you, the ramifications are clear to those of us who do understand some of the physics.  First, I need to provide some background.

Radar (lidar, too) systems emit radio or light signals, that bounce off an object and then determine the time it takes for those signals to return.  This information is then employed to discern the speed of the object, or its position and shape.

Given this data, it is not difficult for someone to generate a photon (a packet of wave energy) that employs the same frequency as the gun and report back data that provides information to confound the sensor’s determinations.  As such, the police (or even opposing armies…) will not be able to determine data of use to them.  (The opposing army may not be able to discern that a warplane is passing by- instead considering it to be a bird or other innocuous object.)

So, Malik et. al. decided they could polarize the emitted photons of light in a predetermined sequence- one known only to them.  That way, the returning photons would not match the keys they employed- unless the jammer was able to guess the sequence they employed.  Even so, many of the polarizations received by the jammer are not able to be discerned, so it will return wrongly polarized signals.

In their experiments, they examined a stealth bomber’s responses.  Photons emitted from non-polarized beams were more than 99% accurate- so the system would not detect the proper shape or size of the bomber.  But, if polarized photons were employed, less than 50% yielded the proper shielding.   (One could also encode a cryptographic key in the signals- this could be even more difficult to discern.)

Now, the trick is to try these experiments outside of the laboratory to see if this works in practice.  If it does, you can bet that not only the military will adopt these techniques, but so will the local (and state) police.

You’ve been warned!

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