Earth as Universe Detector: Scientists Hunt Hidden Forces

SQUIRE Mission to Hunt for Dark Matter and New Physics from Space

A groundbreaking mission, dubbed SQUIRE, is poised to revolutionize the search for dark matter and exotic physics by deploying ultra-sensitive quantum spin sensors aboard the China Space Station. This innovative approach promises to overcome limitations of terrestrial experiments and potentially unlock the secrets of hidden particles and forces governing the universe.

The SQUIRE mission centers on detecting subtle interactions between dark matter particles and ordinary matter, specifically focusing on their spin and velocity. By placing these sensors in orbit, scientists aim to detect these elusive signals with unprecedented precision.

Why orbit is Key to Unlocking Cosmic Secrets

Traditional ground-based experiments struggle to simultaneously maximize both the relative velocity of particles and the number of polarized spins used in detection. SQUIRE elegantly bypasses this challenge by leveraging the unique advantages of the orbital surroundings.

The China Space Station, traveling at approximately 7.67 km/s in low Earth orbit – nearly the first cosmic velocity and 400 times faster than typical laboratory tests – provides a meaningful boost in relative velocity. Furthermore, Earth itself serves as a massive, natural source of polarized spins. “Earth acts as an enormous natural source of polarized spins,” one analyst noted, estimating roughly 10⁴² polarized electrons available, dwarfing the capabilities of terrestrial spin sources by a factor of 10¹⁷.

the orbital motion transforms interaction signatures into predictable, periodic signals, reducing background noise and enhancing detection capabilities.

Projected Sensitivity Gains: A Leap Forward in Detection

The SQUIRE concept is projected to achieve remarkable improvements in sensitivity. The system could detect exotic field amplitudes up to 20 pT, a dramatic increase compared to the 0.015 pT threshold of the best terrestrial detectors. For velocity-dependent interactions, the projected sensitivity improves by an astounding 6 to 7 orders of magnitude for force ranges exceeding 10⁶ meters.

building a Space-Ready Quantum Sensor: Overcoming Orbital Challenges

Developing a robust and sensitive quantum sensor for the harsh space environment presented significant engineering hurdles. Spin sensors in orbit are susceptible to interference from variations in the geomagnetic field, spacecraft vibrations, and cosmic radiation.

To address these challenges, the SQUIRE team developed a prototype incorporating three key innovations:

• Dual Noble-Gas Spin Sensor: Utilizing isotopes of Xenon (¹²⁹Xe and ¹³¹Xe) with opposing gyromagnetic ratios, the device effectively cancels shared magnetic noise while remaining responsive to signals. This provides a 10⁴-fold noise suppression.
• Vibration compensation technology: A fiber-optic gyroscope actively tracks and corrects for spacecraft vibrations, reducing vibration noise to approximately 0.65 fT.
• Radiation-Hardened Architecture: A 0.5 cm aluminum enclosure and triple modular redundancy in the control electronics protect the system from cosmic rays, ensuring continued operation even with module failures.

The prototype has already achieved a single-shot sensitivity of 4.3 fT,demonstrating its readiness for detecting signals with a 1.5-hour orbital period.

Beyond Exotic Interactions: A Space-Ground Quantum Sensing Network

The potential of SQUIRE extends far beyond the search for exotic interactions. The mission proposes a “space-ground integrated” quantum sensing network, linking orbital detectors with those on Earth to enhance sensitivity across a wide range of dark matter models and beyond-Standard-Model physics. This network could explore phenomena like axion halos and test for violations of CPT symmetry.

Looking ahead, the SQUIRE approach could be extended to other planets within our solar system. “As china expands deeper into the solar system, the SQUIRE approach may eventually employ distant planets such as Jupiter and Saturn…as large natural spin sources,” according to a company release. This long-term vision promises to open new frontiers in our understanding of the universe and the fundamental laws of physics.