A research team led by WANG Xin, JIANG Min, and PENG Xinhua at the University of Science and Technology of China has developed an 87Rb atomic magnetometer with a sensor head volume of just 7cm³.
In a paper published online on September 8, 2026 in Acta Physica Sinica, the researchers report total system power consumption under 5W and a reference sensitivity of 10pT/√Hz.
On sensitivity alone, commercial scalar magnetometers designed to operate within Earth's magnetic field already surpass this figure. What the research team prioritized instead was the device's ability to track rapid magnetic field changes of up to 25,200nT per second, along with a mechanism that automatically restores resonance lock in under one second whenever it is lost.
The novelty here isn't a record-breaking sensitivity claim—it's building a compact system that can keep measuring outdoors, where Earth's field fluctuations and motion-induced disturbances are unavoidable.
Packing measurement functions into a 7cm³ sensor head
The sensor head houses a vertical-cavity surface-emitting laser (VCSEL), miniature optical components, and a rubidium vapor cell smaller than 1cm on each side.
It also integrates a micro-heater to warm the cell, a thin-film flexible RF coil, and a non-magnetic photodiode.
Measurement relies on optically pumped magnetic resonance: light is shone on rubidium atoms to align their states, the RF coil induces resonance, and the strength of the magnetic field is determined from changes in the transmitted light.
Rather than drastically cutting the number of components, the team miniaturized each part individually and packed them into a single sensor head—resulting in the 7cm³ figure.
However, this 7cm³ refers only to the sensor head itself, not the full system including the electronics for laser control, signal processing, and overall device management.
According to the reported dimensions, the sensor head measures approximately 3×1.5×1.5cm, the internal vapor cell is roughly 4mm per side, and the measurement bandwidth is 41.4Hz.
By comparison, the sensor head of the commercial scalar magnetometer QuSpin QTFM Gen-2 measures 17.7×19.8×35.8mm, which works out to roughly 12.5cm³ when calculated as a simple rectangular volume.
The new 7cm³ design represents about 56% of that figure.
That said, actual products have rounded edges and cutouts, so the 12.5cm³ figure is only a rough estimate based on external dimensions. The two devices also use different measurement principles, so volume alone cannot be used to compare performance.
Still, shrinking the sensor head of an atomic magnetometer that operates directly within Earth's magnetic field down to 7cm³ is meaningful for mounting on small mobile platforms such as drones.
Sensitivity and tracking speed are separate metrics
Earth's magnetic field strength varies by location but is roughly 50,000nT, or about 50 million pT.
A sensitivity of 10pT/√Hz serves as a benchmark indicating the device can detect magnetic field fluctuations of roughly 10pT within a 1Hz measurement bandwidth.
The figure of 25,200nT/s, on the other hand, represents how well the device can maintain its measurement state and keep tracking when the magnetic field changes rapidly.
The ability to detect small field changes and the ability to keep up with rapid field changes are two distinct capabilities.
Lining up the publicly available figures from primary sources helps clarify how this device is positioned relative to others.
| Device | Method | Sensitivity | Response to Field Changes | Power Consumption | Operating Environment |
|---|---|---|---|---|---|
| USTC 87Rb Magnetometer | Optically pumped magnetic resonance | 10pT/√Hz | 25,200nT/s | Under 5W (full system) | Earth's magnetic field |
| QuSpin QTFM Gen-2 | Free induction decay | 3pT/√Hz (typ.) | Manufacturer states no slew rate limit | ~2.5W | 1,000–150,000nT |
| QuSpin QZFM Gen-3 | SERF | Under 15fT/√Hz | Not specified | Not specified | Magnetically shielded environment or near-zero field (±5nT) |
On sensitivity alone, the new device's 10pT/√Hz falls short of the QTFM Gen-2's 3pT/√Hz (typ.).
The gap widens further against the QZFM Gen-3, which requires magnetic shielding and achieves under 15fT/√Hz—three orders of magnitude smaller in unit terms.
However, the QZFM Gen-3 can only operate within a ±5nT field range, making it unusable in environments exposed directly to Earth's roughly 50,000nT field.
The new magnetometer isn't chasing maximum sensitivity. Its target application is tracking magnetic field changes outdoors, amid disturbances, in environments where Earth's field is not canceled out.
Weak magnetic field measurement technology has been used in resource exploration, geomagnetic navigation, environmental monitoring, and detecting the magnetic anomalies created by submarines.
Methods pursuing maximum sensitivity include SQUIDs and SERF-type atomic magnetometers, which reach into the sub-fT range. However, SQUIDs require extreme cryogenic cooling, while SERF devices need magnetic shielding to substantially cancel Earth's field.
For this reason, outdoor measurements typically rely on scalar magnetometers or optically pumped magnetometers that can operate directly within Earth's field.
The device developed here falls into this category of magnetometers designed for outdoor use.
Recovering measurement in under one second after sudden field changes
Optically pumped magnetic resonance magnetometers measure magnetic fields by continuously matching the RF frequency to the atoms' resonance frequency.
However, if the magnetic field changes abruptly or the sensor head's orientation shifts significantly, the device can fall out of resonance and fail to obtain accurate readings.
In this system, the signal derived from transmitted light is continuously monitored, and a significant drop in amplitude is interpreted as a loss of resonance lock.
When this happens, the device automatically sweeps across its measurable frequency range to relocate the resonance point corresponding to the current magnetic field.
According to the research team, this recovery process takes under one second.
For continuous outdoor measurement, the ability to quickly recover from a lost measurement state is just as important as raw sensitivity.
The team conducted three outdoor experiments.
The first involved long-duration geomagnetic monitoring. During a large-scale magnetic storm, the team reported recording the entire sequence of field changes without gaps.
The second experiment measured magnetic fields from ground level above a subway line.
In this environment, temporary field changes exceeding 2,000nT per second occurred, yet the device successfully captured the field variations corresponding to trains passing underground.
The third experiment involved searching for a buried magnet.
A cylindrical permanent magnet was buried roughly 0.5m underground, and researchers walked across a 40×25m area while measuring with the sensor head.
Even while subject to walking-induced vibrations and changes in sensor orientation, the device reportedly captured the magnet's characteristic field distribution and allowed the team to estimate its buried location.
However, no specific figures—such as positioning error in centimeters—were provided.
Additionally, there are conditions under which sensor orientation weakens the interaction between atoms and light. The presence of an automatic recovery function does not mean valid data can always be obtained regardless of orientation or disturbance.
Detecting a subway doesn't mean detecting a submarine
Some overseas media coverage has linked this research to submarine detection.
It's true that the paper mentions anti-submarine warfare as one potential application area for weak-field measurement technology.
However, the outdoor tests actually reported in this study consisted of three activities: long-duration geomagnetic monitoring, subway detection, and locating a buried magnet.
No underwater tests or experiments involving ships or submarines were conducted.
The fact that the device could detect magnetic field changes from trains running underground, or locate a permanent magnet buried roughly 0.5m deep, does not allow us to determine from what distance an actual submarine could be detected.
The paper also provides no figures for detection range or false-alarm rates in a submarine-detection scenario.
The authors' affiliations reportedly include, besides the University of Science and Technology of China, the Hefei National Laboratory and a research institution affiliated with China State Shipbuilding Corporation that specializes in marine navigation and control.
However, the participation of researchers with shipbuilding backgrounds is a separate matter from whether this device has actually demonstrated submarine detection capability.
Measuring conditions at ground level above a subway station differ substantially from those involved in detecting the faint magnetic anomalies produced by an object moving underwater from a distance—factors such as distance to the target, ambient noise, and the vibration and orientation of the platform carrying the sensor all vary greatly between the two scenarios.
This research does not yet include data that bridges that gap.
The research team itself frames this achievement not as a record for maximum performance, but as one approach to deploying high-performance quantum sensing technology in real outdoor environments.
The real story: miniaturization and "the ability to keep measuring"
Research into atomic magnetometers designed for outdoor and mobile use has been underway in China for some time.
In April 2025, China Aerospace Science and Technology Corporation announced a CPT atomic magnetometer intended for drone deployment.
What's particularly noteworthy about this research isn't a new record for absolute sensitivity.
Rather, it's the achievement of shrinking the sensor head to 7cm³, running the entire system on under 5W, tracking magnetic field changes as rapid as 25,200nT per second, and recovering from lost measurement states in under one second.
China is not alone in pursuing this direction.
Japan's Ministry of Defense is also researching the miniaturization of quantum magnetic sensors that use atomic properties to detect weak magnetic field changes, with an eye toward future deployment on unmanned aircraft. However, specific performance figures have not yet been published, so direct comparison with this device isn't possible at this stage.
Determining whether this research will lead to practical systems for applications like submarine detection would require additional data:
Field tests on mobile platforms in real-world environments—including on and under water—actual detection ranges for magnetic anomalies, false-alarm rates when distinguishing targets from ambient magnetic noise, and independent verification by researchers outside the original team.
What has been demonstrated at this stage is not "a compact quantum sensor capable of detecting submarines."
Rather, it is the successful prototyping of an atomic magnetometer with a 7cm³ sensor head that can sustain measurements even outdoors amid large magnetic field fluctuations—confirmed through multiple field tests.