GPS began its life as a military technology in the 1970s, then everything changed in the late 80s when the US government decided to allow civilian use of the satellite network. Virtually every mobile device on the planet has a GPS chip built-in that lets you find your way around, but GPS is getting old and doesn’t work well in all situations. The British Ministry of Defence is hard at work developing a so-called “quantum compass” that could become the successor to GPS, and just like GPS, it might land in your pocket one day.

The UK military is investing millions of pounds in the quantum compass mainly for use in submarines. GPS systems require a view of the sky, or at least very little obstruction to get a location fix. A tube of metal sliding through the water 100 meters beneath the waves can’t really get a GPS lock. Subs currently use a type of inertial location system based on accelerometers. Each twist and turn a submarine makes is recorded and used to calculate its position based on the last known coordinates. This is called dead reckoning navigation.

So it has a wicked cool name, but dead reckoning is only as good as the system it’s built on, and accelerometers aren’t very good. Submarines can regularly drift more than a kilometer off course after being submerged for a day. A quantum compass could replace the accelerometers and provide extremely precise location analysis for long periods of time underwater. [Read: Think GPS is cool? IPS will blow your mind.]

A quantum compass takes advantage of the 1997 Nobel-winning discovery that lasers can be used to cool atoms to within fractions of a degree of absolute zero. Atoms in this frozen state are extremely sensitive to the magnetic and gravitational field of the Earth. Thus, they can be used to track movement with amazing accuracy. To be clear, this is still a type of inertial “dead reckoning” navigation. The difference is that after getting a solid GPS lock, a sub could go underwater and be exactly on target when it surfaces days or even weeks later.

The prototype compass build by the Ministry of Defence resembles a 1-meter-long shoe box. Inside is an array of lasers cooling a tiny cloud of rubidium atoms. Three such devices could be placed at right angles to each other to measure movement along all three axes. The next step is to miniaturize the technology, perhaps making it compact enough to be integrated in a single chip.

But why go to all this trouble for submarines? Well, that’s not the only reason for governments to move away from satellite positioning systems. The US has long warned that the signals from GPS satellites could be interfered with or hijacked to corrupt location information. Additionally, as international tensions mount over space, several countries (most notably China) have tested satellite-busting weapons that could cripple GPS and leave space strewn with junk. And of course, the US could always cut off other countries and civilians from using its GPS network.

If a quantum compass ever makes its way into your smartphone, it will probably still be paired with some sort of GPS system. It needs a point of reference to calculate your position with those super-cooled atoms. Of course, it might only need to fire up the GPS once every few days or weeks to recalibrate the compass.