Quantum sensor breakthrough could one day replace global GPS systems

Thanks to the miracle of GPS we can now work out where we are almost anywhere on Earth, but it has its flaws. It doesn’t work well everywhere. For example, go inside buildings, underground in a cave, or underwater in a submarine and the GPS signal dies. As a result it’s no wonder that researchers and military complexes around the world, including China who recently just dropped a cool $10 Billion to address the problem at their new national Quantum technology lab, are looking for alternatives.

One alternative, which has just been prototyped by a team at NIST in the US uses the combination of the detection of Very Low Frequency (VLF) magnetic signals from the Earth and using Quantum Sensors, which are millions times more sensitive than today’s sensor systems, based on atoms of Rubidium, to detect them.

"The big issues with VLF [fields] is poor receiver sensitivity and the extremely limited bandwidth of today’s existing transmitters and receivers, which means the data rate is zilch," says NIST project leader Dave Howe, “Rubidium atoms offer very fast response plus very high sensitivity. Classical communications involve a trade off between bandwidth and sensitivity, but now we can get both using our Quantum sensors.”

"Their increased sensitivity leads in principle to longer communications range. The quantum approach also offers the possibility to get high bandwidth communications like a cell phone has," he added.

The sensors work like a magnetometer. As the magnetic fields reach the Rubidium, the spin rate of the atoms in the sensor changes and this creates a current that can be measured, and the sensors are capable of detecting magnetic signals a million times smaller than Earth’s magnetic field.

The advantages of this approach vary though. The teams quantum sensors work at room temperature, they’re small, they consume very little power, and they should be relatively cheap to make. They also don’t require calibration because they use the naturally occurring properties found in the Rubidium atoms, and these facts make them a really strong contender to replace today’s GPS systems. But despite their advantages, there are still challenges ahead and the path ahead to get to the point where the new technology can be commercialised is a long one.

Firstly, there are many magnetic fields around, so the signal can sometimes become lost in the noise, and secondly the teams new system has an indoor range of tens of meters. It also struggles with accurate positioning. At the moment it can locate someone with an accuracy of 16 meters but the researchers want to get that down to 3 meters where it will start matching today’s commercial, consumer grade GPS systems.

As for what’s next, well Howe and his team are now working on ways to increase the signal to noise ratio by improving how the magnetic field is produced, among other things.