CAS Center for Excellence in Quantum Information and Quantum Physics, School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China.
Department of Precision Machinery and Precision Instrumentation, Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes, University of Science and Technology of China, Hefei 230027, China.
Phys Rev Lett. 2023 May 19;130(20):201401. doi: 10.1103/PhysRevLett.130.201401.
Among the four fundamental forces, only gravity does not couple to particle spins according to the general theory of relativity. We test this principle by searching for an anomalous scalar coupling between the neutron spin and the Earth's gravity on the ground. We develop an atomic gas comagnetometer to measure the ratio of nuclear spin-precession frequencies between ^{129}Xe and ^{131}Xe, and search for a change of this ratio to the precision of 10^{-9} as the sensor is flipped in Earth's gravitational field. The null results of this search set an upper limit on the coupling energy between the neutron spin and the gravity on the ground at 5.3×10^{-22} eV (95% confidence level), resulting in a 17-fold improvement over the previous limit. The results can also be used to constrain several other anomalous interactions. In particular, the limit on the coupling strength of axion-mediated monopole-dipole interactions at the range of Earth's radius is improved by a factor of 17.
在四种基本力中，根据广义相对论，只有引力与粒子自旋没有耦合。我们通过在地面上寻找中子自旋与地球引力之间异常标量耦合来检验这一原理。我们开发了一种原子气体共磁强计来测量 ^{129}Xe 和 ^{131}Xe 之间核自旋进动频率的比值，并在传感器翻转到地球引力场时，将这个比值的变化精确到 10^{-9} 的水平进行搜索。这个搜索的零结果将地面上中子自旋与引力之间的耦合能量上限设定在 5.3×10^{-22}eV（95%置信水平），比之前的上限提高了 17 倍。这个结果还可以用来限制其他几种异常相互作用。特别是，在地球半径范围内，轴子介导的单极-偶极相互作用的耦合强度上限提高了 17 倍。
