Tube trains could navigate the Underground using the rules of Quantum Physics

Summary

Tube trains of the future may soon know exactly where they are underground — even in places where GPS is blind — by tapping into the strange rules of the quantum world. Imperial College quantum accelerometer Most modern tracking systems rely on satellites to pinpoint location, backed up by accelerometers that measure tiny movements between GPS updates. It works well enough above ground, but those accelerometers gradually drift, which is why they constantly need satellite corrections. However, in tunnels or urban areas surrounded by tall buildings where GPS signals don’t reach, that safety net disappears. So researchers are turning to something far more exotic: quantum accelerometers. Instead of relying on conventional sensors, these devices use clouds of atoms cooled to near absolute zero. At those temperatures, atoms start to behave strangely — acting as both particles and waves. As the atoms “fall” through a sensor, their wave patterns shift in response to acceleration. Using what’s effectively an ultra-precise optical ruler, the system can read these changes with extraordinary accuracy, without needing satellites at all. That technology is now moving closer to the railway. Research firm MoniRail has secured an additional £1.25 million from the UK government’s quantum technology programme to advance the work. The funding supports the next phase of the Rail Quantum Inertial Navigation System (RQINS) roadmap, aimed at developing quantum navigation for the London Underground — and potentially the wider national rail network. MoniRail’s approach goes beyond simple positioning. Sensors fitted to trains already provide a non-intrusive way to monitor track condition, collecting ride-quality data and flagging emerging faults in real time. Naturally, trains already have track-based location systems, but they are usually based on a train being within a “moving block”, so their accuracy is down to metres rather than centimetres. If you want to monitor track conditions, the m...