A groundbreaking initiative named SQUIRE (Space-Based Quantum precision measurement on Exotic Interactions) is setting the stage for a revolutionary leap in the search for ultralight exotic bosons, a pivotal candidate in the quest to unlock the mysteries of dark matter and beyond-Standard-Model physics. Utilizing the extraordinary environment of low Earth orbit, this project aims to harness space’s unique conditions to probe with unprecedented sensitivity the subtle energy shifts induced by exotic interactions that have eluded terrestrial detectors.
At its core, the SQUIRE experiment targets the detection of exotic-boson-mediated interactions, which theoretically manifest in sixteen distinct forms; fifteen of these are spin-dependent, and ten exhibit velocity dependence. Such interactions, if present, subtly perturb atomic energy levels, creating pseudomagnetic fields that can be sensed using highly sensitive quantum spin sensors. The project’s ingenuity lies in deploying these quantum sensors aboard the China Space Station, transforming it into a celestial laboratory uniquely capable of overcoming significant terrestrial limitations in the simultaneous enhancement of two critical parameters: the relative velocity between detector and source, and the number of polarized spins involved.
One of the foremost advantages of conducting this search from space is the inherent high orbital velocity of the China Space Station, cruising at approximately 7.67 km/s. This velocity closely approaches the first cosmic speed, representing a factor of nearly 400 times higher than the relative velocities achievable in laboratory setups with moving spin sources. This dramatic increase intensifies the potential interaction signals, translating subtle quantum effects into measurable data that would otherwise be lost amid terrestrial noise. Furthermore, Earth itself serves as a colossal polarized spin reservoir, hosting roughly 10⁴² unpaired geoelectrons in its mantle and crust, naturally polarized by geomagnetic fields. This number dwarfs laboratory sources by an astonishing seventeen orders of magnitude, offering an unparalleled spin ensemble for interaction detection.
The orbital dynamics of the space station add another layer of experimental sophistication. The station’s approximately 1.5-hour orbit induces a characteristic periodic modulation in the exotic interaction signals, moving them into a frequency regime around 0.189 mHz. This frequency domain offers intrinsically lower noise levels than static direct current (DC) fields, thus significantly enhancing the signal-to-noise ratio and elevating the experiment’s overall sensitivity. Combined, these factors enable the SQUIRE experiment to push the bounds of detection, achieving field sensitivities up to 20 picotesla (pT) for exotic fields—over a thousandfold improvement when compared to the terrestrial benchmark of around 0.015 pT.
Central to this ambitious mission is the development of a space-qualified quantum sensor prototype designed to endure and perform in the harsh environment of orbit. The space quantum sensor is engineered to maintain exceptional sensitivity and stability despite challenges such as geomagnetic fluctuations, mechanical vibrations from the platform, and cosmic radiation exposure. Mitigating these disturbances necessitates advanced technological integration and innovative engineering solutions.
The sensor features a dual noble-gas spin system employing isotopes of xenon (^129Xe and ^131Xe) with opposing gyromagnetic ratios, enabling the simultaneous suppression of common-mode magnetic noise while retaining sensitivity to exotic spin-velocity interactions (SSVIs). This dual-spin approach achieves an extraordinary four orders of magnitude reduction in magnetic noise. Augmenting this design is a multi-layer magnetic shielding apparatus, which further reduces geomagnetic interference down to the sub-femtotesla regime, unlocking a new realm of measurement precision.
Vibration noise, a significant interference factor for sensitive spin sensors in orbit, is actively countered through fiber-optic gyroscope technology. This vibration compensation system diminishes the mechanical noise to a negligible 0.65 femtotesla, preserving the integrity of the measurement signal. Additionally, the system incorporates a radiation-hardened architecture, including a 0.5 cm aluminum enclosure and triple modular redundancy in its control electronics. This design ensures resilience against cosmic ray damage, maintaining operational continuity even if two out of three circuits fail, thus limiting system disruptions to less than one event per day.
Collectively, these innovations endow the SQUIRE prototype sensor with a single-shot sensitivity of 4.3 femtotesla over approximately 1165 seconds, precisely tailored to detect signals modulated at the space station’s orbital period. This technical achievement paves the way for high-precision, on-orbit searches for exotic spin-velocity couplings and other beyond-Standard-Model signatures that might manifest in the ultralight boson landscape.
Beyond the immediate scope of exotic interaction detection, the SQUIRE initiative envisions the creation of an integrated space-ground quantum sensing network, linking quantum spin sensors aboard the China Space Station with terrestrial counterparts. This network aspires to amplify detection sensitivity across a spectrum of elusive phenomena, including additional exotic interactions, axion halos, and potential Charge-Parity-Time (CPT) symmetry violations. Such a synergistic approach could broaden the horizons of fundamental physics research and accelerate the discovery of new particles and interactions.
This integrated sensing strategy leverages the high orbital velocity benefit in multiple ways, facilitating enhanced coupling between axion halos—putative candidates for dark matter—and nucleon spins. Early analyses suggest that the networked approach could improve sensitivity by an order of magnitude over current ground-based direct dark matter detection efforts, marking a significant advance in the field.
Looking forward, the SQUIRE framework holds promise for expansion beyond Earth’s orbit. As China’s deep space exploration efforts progress, exploiting polarized particle sources on distant celestial bodies such as Jupiter or Saturn offers tantalizing possibilities. These planets, rich in naturally polarized particles, could serve as vast natural sources, extending the sensitivity and reach of quantum sensing networks into the far reaches of the solar system. This cosmic-scale vision positions SQUIRE not only as a pioneering dark matter detector but also as a catalyst for the next generation of space-based fundamental physics experiments.
In sum, the SQUIRE project epitomizes the formidable synergy between quantum precision measurement and space technology. By riding the wave of low Earth orbit conditions and leveraging Earth’s massive polarized spin pool, it redefines the experimental landscape for detecting exotic bosonic interactions. Achieving sensitivity enhancements of six to seven orders of magnitude for velocity-dependent interactions at meter-scale ranges, it arms physicists with a tool of unprecedented power to probe uncharted regions of the dark sector and the fundamental fabric of the universe.
This bold endeavor stands at the intersection of quantum mechanics, astrophysics, and space engineering, heralding a new era where orbital platforms become essential observatories for the most subtle and profound forces shaping our cosmos.
Subject of Research: Space-based quantum precision measurement of ultralight exotic boson interactions using dual noble-gas spin sensors aboard the China Space Station.
Article Title: Not provided.
News Publication Date: Not provided.
Web References: DOI: 10.1093/nsr/nwaf389
References: Not explicitly provided beyond the DOI link.
Image Credits: ©Science China Press
Keywords
SQUIRE, exotic bosons, quantum spin sensors, space quantum sensor, China Space Station, ultralight bosons, dark matter detection, spin-velocity interaction, dual noble-gas sensor, fiber-optic gyroscope, radiation hardened, precision measurement, space-based quantum sensing, axion halos, CPT violation, deep space exploration
