London Underground hosts tests for 'quantum compass' that could replace GPS
Researchers are testing a “quantum compass” on the London Underground: an ultra-precise, atom-based accelerometer intended to enable inertial navigation without GPS, especially underground, underwater, or in GPS‑denied military environments. Commenters explain how the system uses laser‑cooled atoms for highly accurate dead reckoning, but emphasize that like all inertial navigation systems it still accumulates error and would need periodic recalibration from external references. There is broad interest in its potential for jam‑resistant positioning and niche high‑value uses, alongside skepticism about media claims that it could fully replace satellite navigation.
What the device is
- Described as a “quantum compass” but participants say it’s essentially a quantum-enhanced inertial navigation system (INS) / dead-reckoning device.
- Core component is a highly sensitive accelerometer; combines known starting position with integrated acceleration to track motion without external signals.
- London Underground is mainly a convenient moving lab; primary envisioned uses are in GPS-denied environments (submarines, underground, underwater, other planets).
How it works (technical discussion)
- Uses cold atoms (rubidium) and laser cooling: atoms are slowed and trapped, then their motion is probed via laser light.
- Because the atoms are referenced to extremely stable laser wavelengths, the accelerometer can, in principle, be more accurate than conventional MEMS or light-based sensors.
- Atoms sit in ultra-high vacuum; cooling is via lasers and traps, not cryogenic liquids.
Accuracy, drift, and recalibration
- All INS approaches accumulate error due to double integration of noisy acceleration data; participants emphasize this remains true here.
- Sampling limits (Nyquist issues) and missed high-frequency accelerations still cause drift.
- Example commercial quantum accelerometer cited with precision that would drift tens of centimeters per hour, hundreds of meters per day if never recalibrated.
- Some note that reduced drift could make recalibration infrequent, especially when combined with known track layouts or station references.
Relationship to GPS/GNSS
- Strong pushback on the idea that this “replaces” GPS; more accurate framing is “GNSS-independent backup” or “augmentation.”
- Devices still require a starting reference and periodic corrections (e.g., from known positions, wireless networks, beacons).
- Counterargument: for military or critical applications in jammed or wartime scenarios, such systems could function as a de facto GPS replacement.
Use cases and deployment contexts
- Suggested uses: submarines, long-range missiles, autonomous underwater/underground vehicles, pipelines, fiber routes, arctic navigation.
- For trains, many argue odometers plus track maps and station resets already provide excellent inertial navigation; quantum tech is overkill.
Miniaturization and practicality
- Current systems are large; bulk comes from optics and electronics, not cryogens.
- Some are optimistic about shrinking to “orange-sized” units over time; others think they’ll remain backpack-scale and niche.
- Several see this as an incremental but important improvement, while a few suspect hype and easy funding rather than transformative tech.