GPS, the Global Positioning System we rely on for guiding nuclear missiles and steering tourists to Mount Rushmore, has become a ripe target for enemy attack. In response, U.S. scientists are developing new ways to circumvent blocked GPS signals using matter waves to measure acceleration.

GPS is vulnerable because the radio signals that satellites broadcast to receivers, such as those in smart phones and  in cars, are so weak that even low-power jammers can easily block them. (GPS devices use the signals from several satellites to triangulate their position.) During the past decade, China and other countries have put satellites for their own regional navigation systems into orbit that work on different frequencies, which means that on a battlefield they could block U.S. signals without disrupting their own.

To get around this potential risk, U.S. scientists are developing gadgets that can track an object’s position in the event GPS signals are cut off. These inertial measurement units, or IMUs, determine a target’s location by measuring changes in acceleration since the last GPS reading. Until now such devices, based on a variety of technologies from mechanical to laser-based, have often been bulky and prone to error after prolonged use. By taking advantage of the quantum-mechanical properties of matter, however, engineers have come up with gadgets that could prove 1,000 times more accurate.

These “cold atom” devices use lasers and magnets to confine clouds of atoms into a very narrow range of energies, explains Werner J. A. Dahm, the U.S. Air Force’s chief scientist. (Such constraints make them “cold” in a quantum-mechanical sense, not in temperature.) Under these conditions, scientists can detect matter behaving like a wave. The devices split these matter waves in two and send each part in opposite directions before bringing them back together. If the device moves while the waves are split apart, one wave will experience acceleration slightly before its counterpart. The laser detects this change when the waves recombine. Because the waves have very small wavelengths—billionths of a meter in size—scientists can use them for ultraprecise measurements of acceleration. The gadgets might be ready for wide-scale use within a decade.

10 Comments

1. 1. bobaug 01:42 PM 9/29/10

   The article states "GPS devices use the signals from several satellites to triangulate their position" whereas the actual process is that of trilateration, the measurement of three distances (and time) to determine position.
   
   Robert Augustson
   

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2. 2. jtdwyer 09:06 AM 10/15/10

   If I understand the teaser article, this essentially provides a quantum precision inertial navigation system, to plot the device's positional motion.
   
   It's good to see the military thinking about the vulnerability of GPS, on which it is so widely dependent. One would think the military has long been aware of its reliance on a indefensible technology, but they just kept increasing battlefield dependence on the technology...

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3. 3. jtdwyer 09:10 AM 10/15/10

   I'm just a pedestrian, but doesn't this implementation of quantum technology confirm my understanding that matter intermittently materializes in either a wave or a particle, and that, at quantum scales, only wave state material energy can propagate through space?

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4. 4. dr777who 10:55 AM 10/15/10

   can this be used for people
   who go into the woods
   
   hunters hikers others

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5. 5. tomsmith 05:31 PM 10/15/10

   When I first worked stepped onto a 'modern' submarine, not that many years ago, I was amazed that the navigation technology used was less sophisticated than the tech I was using on my own sea kayak ... a big part of submarine navigation is the IMU which it uses to 'guess' where it is between surfacing. Over time, the accuracy of estimation degrades, so that when plotting a submarine course for you end up having to give it enormous buffer zones on both sides, just in case it happens to end up on the edge of its envelope.

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6. 6. jtdwyer in reply to tomsmith 05:49 PM 10/15/10

   Hopefully this atomic scale analog of old inertial navigation systems will be much more precise, but I'd guess that drift could still occur to some extent, perhaps depending on 3D mapping accuracy.
   
   Since I guess that submarines cannot receive GPS satellite signals when submerged, do they now periodically surface to correct with GPS or star sightings, potentially revealing their position? (please do not reveal any classified info.) If so, this could provide a critical improvement in strategic and tactical submersible navigation!

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7. 7. scientific earthling 07:29 PM 10/15/10

   If an enemy nation has its own satellites for GPS functioning on different frequencies and yours are blocked, how hard is it to use their satellites to determine your position?

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8. 8. ennui 08:36 PM 10/15/10

   THere is stated that the Chinese use differeent frequencies for their GPS and in case of hostilities they can zap our Gps, while theirs stays intact. We can zap theirs too without affecting ours.
   Something like using gas in WWII. The Germans never went anywhere without their gas mask. If they had used gas against our troops, all of Germany would have been anthraxed. No gas in WWII.

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9. 9. metaman 08:07 PM 10/16/10

   This is just inertial navigation updated to use quantum methods. Laser gyroscopes have been in use for decades in the military. Nice to see the value of quantum physics when applied to existing technology.

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10. 10. jtdwyer in reply to metaman 03:13 AM 10/18/10

    Thanks for corroborating the assessments and opinions expressed in previous comments.

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