https://www.engadget.com/2018/11/11/quantum-compass/
"GPS is vital to modern navigation, but it's extremely fragile. Never mind coverage -- if a satellite fails or there's a jamming attack, it quickly becomes useless. Scientists may have a much more robust answer, though. Scientists have demonstrated a "commercially viable" quantum accelerometer that could provide navigation without GPS or other satellite technology. The device uses lasers to cool atoms to extremely low temperatures, and then measures the quantum wave properties of those atoms as they respond to acceleration. The result is an extremely sensitive device that's also considerably more reliable than conventional accelerometers. While existing hardware can help determine to location to some extent by measuring velocity, it quickly falls apart without help from space. As you might have noticed by looking at the photo above, this quantum 'compass' isn't ready to replace the accelerometer in your phone. It's only truly ready for ships, trains and other large vehicles where size and power requirements aren't major factors. It could keep transportation networks humming even if GPS fails outright. The researchers also expect the underlying concepts to help with science studies, such as looking for gravitational waves. [end of quote] https://phys.org/news/2018-11-quantum-compass-satellites.html "The UK's first quantum accelerometer for navigation has been demonstrated by a team from Imperial College London and M Squared. Most navigation today relies on a global navigation satellite system (GNSS), such as GPS, which sends and receives signals from satellites orbiting the Earth. The quantum accelerometer is a self-contained system that does not rely on any external signals. This is particularly important because satellite signals can become unavailable due to blockages such as tall buildings, or can be jammed, imitated or denied – preventing accurate navigation. One day of denial of the satellite service would cost the UK £1 billion. Now, for the first time, a UK team has demonstrated a transportable, standalone quantum accelerometer at the National Quantum Technologies Showcase, an event demonstrating the technological progress arising from the UK National Quantum Technologies Programme – a £270m UK Government investment over five years. The device, built by Imperial College London and M Squared, was funded through the Defence Science and Technology Laboratory's Future Sensing and Situational Awareness Programme, the Engineering and Physical Sciences Research Council, and Innovate UK. It represents the UK's first commercially viable quantum accelerometer, which could be used for navigation. Accelerometers measure how an object's velocity changes over time. With this, and the starting point of the object, the new position can be calculated. Using the precision of ultra-cold atoms Accelerometers have existed for some time, and are present today in technologies like mobile phones and laptops. However, these devices cannot maintain their accuracy over longer periods without an external reference. [end of quote]
