Quantum precision measurements set another international record at CSU
Professor Xinhua Peng and Associate Researcher Min Jiang at the Key Laboratory of Microscopic Magnetic Resonance, Chinese Academy of Sciences, University of Science and Technology of China, have made important progress in the field of quantum precision measurement and testing beyond the standard model, using self-developed quantum spin amplification technology to achieve ultra-sensitive testing of a class of cosmological broken interactions beyond the standard model. The experimental results have improved the international record by at least 5 orders of magnitude, bridging the gap in existing astronomy.
The research results were published online on January 6 in the international journal Science Advances under the title "Search for exotic parity-violation interactions with quantum spin amplifiers". Advances [Sci. Adv. 9, eade0353 (2023)].
The Standard Model of particle physics is one of the greatest models established by physics in the 20th century. However, despite the great success of the Standard Model, many physical phenomena such as dark matter, dark energy, neutrino oscillations, and positive and negative matter asymmetry could not be well explained. For this reason, many theories have predicted the possible existence of new light bosons beyond the Standard Model, such as axions, dark photons, Z-bosons, etc., which can be used as dark matter candidates to complement the existing Standard Model theories. The energies of these new particles may span a range of several tens of orders of magnitude. For new particles in the low energy region (much less than 1 eV), the volatility of the particles is even more pronounced, and their de Broglie wavelengths are even larger than those of today's large colliders, making them unsuitable for study using high-energy devices such as particle colliders and gas pedals. Quantum sensors such as atomic magnetometers and atomic clocks fill the detection gap of such ultra-light dark matter candidates in high-energy devices, but because the interaction of these new particles with particles inside the Standard Model is very weak, a highly sensitive quantum sensor is urgently needed to study the new physics outside the Standard Model.
Fig. 1 Experimental setup for testing the new interaction and the corresponding magnetic detection sensitivity.
Using the recently developed quantum spin amplifier technology (Fig. 1A) [Nat. Phys. 17, 1402-1407 (2021)], Prof. Xinhua Peng's group has achieved two orders of magnification of the magnetic signal to be measured (Fig. 1B), and applied it to the search for new particles and new interactions beyond the Standard Model, which has been proposed internationally. The "Sapphire" research program, known by the acronym SAHPPHIRE (SpinAmplifier for Particle PHysIcs REsearch), was launched internationally. The first experiments of the program constrained a spin interaction induced by Z bosons, as shown in Figure 1C. These singular interactions are cosmologically non-consistent and their strength is proportional to the number of electron spins in the spin source. Therefore, two atomic gas chambers were used in this experiment, one using noble gas xenon atoms as the spin sensor and one using alkali metal rubidium atoms as the spin source. The alkali metal atom within the spin source is pumped by a laser to achieve an electron polarization spin number of about 1014 and is intermittently polarized by the pump light, resulting in an alternating oscillating singular field acting on the quantum spin sensor, which is further amplified and detected.
In contrast to other resonance techniques applied to new physical searches, the rubidium atoms in the quantum spin amplifier act as embedded magnetometers, enabling continuous polarization and in-situ measurements of the noble gas xenon atoms. In contrast, one of the significant advantages offered by in situ measurements is the enhancement of the nuclear resonance signal due to the large Fermi contact amplification factor. In addition, since the xenon nuclear spins are continuously polarized by spin-exchange collisions with polarized rubidium atoms, the spin amplifier enables a continuous search for singular fields. Due to these unique advantages, spin amplifiers are more suitable for ultra-sensitive continuous-wave detection of singular interactions. Because of this, this experiment has improved the constraints on the cosmological broken singular interactions between electrons and neutrons by five orders of magnitude compared with the international frontier experimental limits (e.g., Fig. 2A), and the singular interactions between neutrons and protons have been explored for the first time (e.g., Fig. 2B). In addition, there is still much room for performance improvement in the SAPPHIRE program, and the researchers propose to use the K-3He spin amplifier with a solid spin source, which is expected to further improve the experimental bound on such singular interactions by 8 orders of magnitude.
Figure 2 Experimental bounds for novel interactions.
The reviewers have high praise for this work: "The result is a clearly a major improvement for the field" and "What is particularly remarkable about these results is that they have established strong new constraints, which have improved prior bounds by several orders of magnitude, in a region of parameter space where there are little or no constraints from astrophysics" and "What is particularly remarkable about these results is that they have established strong new constraints, which have improved prior bounds by several orders of magnitude, in a region of parameter space where there are little or no constraints from astrophysics". strong new constraints were established, improving previous constraints by multiple orders of magnitude). This result demonstrates the organic combination of quantum precision measurement techniques and particle physics research under the SAPPHIRE program, and is expected to stimulate a wide range of interests in several fundamental sciences, including cosmic astronomy, particle physics, and atomic-molecular physics.
Yuanhong Wang and Ying Huang, PhD students at the Key Laboratory of Microscopic Magnetic Resonance, Chinese Academy of Sciences, are co-first authors of the paper, and Prof. Xinhua Peng and Associate Researcher Min Jiang are co-corresponding authors of the paper. The research was funded by the Ministry of Science and Technology, the National Natural Science Foundation of China and Anhui Province.
Link to the paper：
https://www.science.org/doi/10.1126/sciadv.ade0353
