Scientists to Use Earth Itself as a Giant Sensor in Hunt for New Physics

By Science China Press November 14, 2025

Collected at: https://scitechdaily.com/scientists-to-use-earth-itself-as-a-giant-sensor-in-hunt-for-new-physics/

Far above Earth, scientists are using quantum sensors to listen for the faintest whispers of unseen forces that may weave through the universe.

Scientists are constantly searching for new clues about the hidden forces that may exist beyond the known laws of physics. One promising area of research focuses on exotic boson interactions, hypothetical effects that could reveal previously unknown particles or forces.

These interactions are predicted to take 16 possible forms, most of which depend on the spins of particles, with some also linked to their velocity. When they occur, they may cause extremely small changes in atomic energy levels, producing faint pseudomagnetic fields.

Detecting these subtle signals requires incredibly sensitive instruments. The SQUIRE project aims to take this challenge into space by placing quantum spin sensors aboard the China Space Station. These sensors are designed to detect pseudomagnetic fields that might arise from interactions between their own spins and Earth’s geoelectrons.

By combining the precision of quantum measurement with the unique conditions of space, SQUIRE can overcome a major limitation of ground-based experiments: increasing both relative motion and the number of polarized spins at the same time.

Several factors make space an ideal environment for these measurements.

1. The China Space Station travels around Earth at 7.67 km/s, nearly the first cosmic velocity and about 400 times faster than moving sources in laboratory experiments.
2. Earth itself acts as a giant natural source of polarized spins. Unpaired geoelectrons in the planet’s crust and mantle, aligned by the geomagnetic field, provide roughly 10⁴² polarized spins—around 10¹⁷ times more than those in common lab materials like SmCo₅.
3. The station’s orbit naturally turns potential exotic signals into repeating oscillations. With an orbital period of about 1.5 hours, these signals are modulated to around 0.189 mHz, a very low-frequency range where background noise is minimal compared to ground-based setups.

Unprecedented Sensitivity and Detection Potential

Because of these advantages, even under strict physical limits, the SQUIRE system could detect exotic field strengths up to 20 pT, far beyond the 0.015 pT achievable on Earth. Its sensitivity to velocity-dependent exotic interactions over force ranges greater than 10⁶ m is expected to improve by 6 to 7 orders of magnitude.

Building a space-ready quantum spin sensor is central to the SQUIRE mission. The sensor must maintain extremely high sensitivity and stability in the demanding conditions of space. However, such sensors must also deal with three main challenges: changes in Earth’s magnetic field, vibrations from the spacecraft, and exposure to cosmic radiation.

To address these, the SQUIRE team developed a prototype integrating three breakthrough technologies: (i) Dual Noble-Gas Spin Sensor: Using ¹²⁹Xe and ¹³¹Xe isotopes with opposite gyromagnetic ratios, the sensor suppresses common-mode magnetic noise while preserving sensitivity to SSVI signals. This achieves 10⁴-fold magnetic noise suppression, and combined with multi-layer magnetic shielding, reduces geomagnetic fluctuations to sub-femtotesla. (ii) Vibration Compensation Technology: Equipped with a fiber-optic gyroscope, the system actively compensates for platform vibration, reducing noise to a negligible 0.65 fT. (iii) Radiation-Hardened Architecture: A 0.5 cm aluminum enclosure and triple modular redundancy in control circuits mitigate cosmic ray impacts. This ensures functionality even if two of three redundant circuits fail, reducing disruptions to <1 per day.

Integrating these technologies, the SQUIRE prototype achieves a single-shot sensitivity of 4.3 fT @ 1165 s—ideal for detecting SSVI signals with a 1.5-hour period—laying a solid technical foundation for on-orbit high-precision dark matter detection.

Beyond SQUIRE: A Space-Ground Quantum Network

Beyond exotic interaction searches, quantum spin sensors on the China Space Station will enable a wide range of fundamental physics research in space. SQUIRE envisions a “space-ground integrated” quantum sensing network, linking orbital and terrestrial sensors to dramatically enhance sensitivity across multiple dark matter models and beyond-Standard-Model phenomena, including other exotic interactions, Axion halos, and CPT violation probes.

Specifically, high-speed orbital motion enhances coupling between axion halos and nucleon spins, achieving a 10-fold sensitivity improvement over terrestrial direct dark matter searches. As China’s deep space exploration advances, the SQUIRE framework will inspire the use of distant planets (e.g., Jupiter and Saturn, rich in polarized particles) as natural polarized sources, expanding the frontiers of physics exploration on cosmic scales.

Reference: “Quantum sensors in space: unveiling the invisible universe” by Yuanhong Wang, Xingming Huang, Min Jiang, Qing Lin, Wenqiang Zheng, Yuan Sun, Liang Liu, Xinhua Peng, Zhengguo Zhao and Jiangfeng Du, 22 September 2025, National Science Review.
DOI: 10.1093/nsr/nwaf389