Quantum magnetometers can detect incredibly small changes in magnetic fields by tapping into the strange and powerful features of quantum physics. These devices rely on the discrete nature and coherence of quantum particles—behaviors that give them a major edge over classical sensors. But how far can their sensitivity go? And what actually makes a magnetometer “quantum?”
A new study explores the theoretical boundaries of these devices, comparing multiple methods for defining their limits. The findings shed light not only on performance but also on what truly separates quantum sensors from their classical counterparts.
Quantum Magnetometers and Ultra-High Sensitivity
Quantum magnetometers can detect magnetic fields with extremely high sensitivity by leveraging the unique behaviors of quantum particles. These behaviors — such as discreteness and quantum coherence (including entanglement) — enable a level of precision that classical sensors cannot easily match. Thanks to these advantages, quantum magnetometers are now widely used in fields such as fundamental physics, non-invasive medical diagnostics, and remote sensing.
The Big Questions in Quantum Magnetometry
In the study of quantum magnetometry, two fundamental questions have drawn significant interest: What is the ultimate limit to how sensitive a magnetometer can be? And how can we determine whether a magnetometer is truly operating based on quantum principles?
One should be careful whenever using the word "ultimate."
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