What makes a sensor “quantum”
Quantum sensors measure a physical quantity through its effect on well-defined quantum states — the energy levels of atoms or the spin of electrons in a crystal. Because those states are set by nature rather than by manufacturing tolerances, many quantum sensors offer excellent stability or measurements tied closely to fundamental constants. That does not automatically make them better in the field: environment, size, power and integration usually decide.
The main types
| Type | Measures | Strength | Main limitation |
|---|---|---|---|
| Optically pumped (OPM / SERF) | Magnetic field | Very high sensitivity1 | Highest-sensitivity (SERF) mode needs near-zero field, usually shielding2 |
| SQUID | Magnetic field | Extreme sensitivity | Cryogenic cooling drives total power and size2 |
| NV diamond | Magnetic field (vector) | Room-temperature, solid-state3 | Laser and microwave power; far from theoretical limits today3 |
| Atomic clock (incl. chip-scale) | Time / frequency | Stable timing without GNSS4 | Chip-scale clocks trade precision for size and power4 |
| Cold-atom interferometer | Acceleration, rotation, gravity | Low drift | Low update rate, limited dynamic range, relatively large SWaP5 |
| Rydberg-atom RF | Radio-frequency electric field | SI-traceable, self-calibrated measurement6 | Laser and vapour-cell complexity |
For reference, a good conventional fluxgate magnetometer reaches roughly 10 pT/√Hz.2
Where they are used
- Navigation — magnetic anomaly and gravity-aided navigation, and quantum inertial sensors that are typically hybridised with conventional ones.7
- Timing — chip-scale atomic clocks, of which NIST reports more than 100,000 sold, hold time when GNSS is unavailable.4
- Geophysics and exploration — magnetic and gravity surveys.
- Metrology and RF — traceable field measurements such as Rydberg-atom probes.6
How to read a quantum sensor specification
- Sensitivity needs context. A figure in pT/√Hz means little without the frequency band, whether it was shielded or unshielded, and whether it is the sensing element or the complete module.
- Look at the whole budget. Size, weight and power should include lasers, electronics and any cooling or heating.
- Check operating envelope. Field range, orientation dependence (dead zones, heading error), temperature and vibration.
- Ask for test conditions. Who measured it, how, and over what duration.
Common misconceptions
- “Quantum means better.” Only for particular measurements and conditions; mature classical sensors often win on cost and robustness.
- “A more sensitive sensor gives a better system.” System performance is usually limited by platform noise, maps, models or integration.
- “Quantum sensing needs a quantum computer.” It does not; these are standalone instruments.
About this resource
Orbital Quantum is a Canadian company developing True North Navigation™ quantum magnetometer modules for GPS-independent positioning, currently offered as Founder's Edition units for partner evaluation ahead of broader commercial release. See how True North Navigation works.
Sources
- arXiv:1404.0374 — SERF-regime rubidium magnetometry — arxiv.org
- MDPI Sensors 21(16):5568 — Precision magnetometers for aerospace applications: a review (2021) — www.mdpi.com
- Barry et al. — Sensitivity optimization for NV-diamond magnetometry, Rev. Mod. Phys. (2020) — arxiv.org
- NIST — Success story: chip-scale atomic clock — www.nist.gov
- Frontiers in Physics — Cold atom inertial sensors for navigation applications (2022) — www.frontiersin.org
- NIST — Rydberg atom-based quantum RF field probes — www.nist.gov
- Tennstedt et al. — Atom strapdown, NAVIGATION 70(4) (2023) — navi.ion.org
Published by Orbital Quantum. Last reviewed 25 September 2026. Figures are illustrative unless a source is cited.