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The "quantum compass" sounds like something Dr Who might use, or a 1990s special edition car name. In actuality, it's the name of a new device under development with the British military to allow GPS-style navigation in submarines without the use of satellites.
The big news here is that GPS itself was originally developed by the military—but now it's in your smartphone, or available for a hundred bucks from an electronics store, or you can spend a little more than that to have satellite navigation embedded in your car's dashboard. In other words, it's not a great leap to imagine every car having its own quantum compass in a few decades' time.
According to GPS Daily (via Autoblog), the quantum compass uses the movements of super-cooled subatomic particles to pinpoint a vessel's location. These particles, stored in a vacuum, react to the Earth's magnetic field. The movements caused by this interaction can be used for location positioning. It's a great deal more accurate than the current method used by submariners, which relies on accelerometers to pick up a vessel's movement while underwater. The accuracy difference is enough that a vessel surfacing after a day could be within three feet of its intended position--rather than up to a mile off.
At the moment, the Ministry of Defense's prototype resembles a "1-meter long shoe box", so the next step is to miniaturize it. It could then be used by individual soldiers, as well as huge ships and submarines. Not only is it useful, but it's secure too—the technology is apparently interference-proof. This, naturally, is more useful in a military application than it is to someone going on vacation in their car, but the quantum compass's accuracy could be beneficial to everyone.