Measuring the electron electric dipole moment using an array of ultracold molecules

粒子物理学的标准模型是现代科学最伟大的成就之一。它在对基本粒子进行分类并解释它们的行为方面取得了令人难以置信的成功。然而，人们普遍认为标准模型是不完整的，因为它不能解释几个重要的观察结果。一个突出的例子是宇宙中物质多于反物质。标准模型预测物质和反物质的数量几乎相等，但观测显示宇宙只包含物质。这一矛盾是现代物理学中尚未解决的重大问题之一，也是我们最基本理论的一个重大缺陷。为了建立一个更完整的宇宙图景，物理学家正在努力揭示标准模型之外的东西。这是在巨型粒子加速器上进行的许多研究的一个重要目标。还有另一种巧妙的方法来探索同样的问题——测量电子的形状。解释物质/反物质不平衡所需的新作用力也使电子稍微非球形。这种扭曲——被称为电偶极矩——改变了电场中电子的能量，当电子与分子结合时，这种微小的变化会被放大。我建议建造一种仪器，使用一组冷却到微开尔文温度的分子，对电子的形状进行极其精确的测量。通过非常仔细的测量，这样的桌面实验使我们能够探测到与粒子加速器达到的能量相等，甚至更高的能量。由于我最近成功地将分子冷却到极冷的温度，这种惊人的精确度成为可能。这项技术是本提案的基础。我的计划是，利用精心调谐的激光施加的力，使一束单氟化镱分子减速，使其静止，捕获这些分子，并将它们冷却到几微开尔文。然后，我会把它们装进一系列由驻波组成的陷阱里。该阵列包含数百万个单独的陷阱，并将分子彼此隔离，为测量电子的电偶极矩创造了一个原始的环境。这种测量是通过观察分子在外加磁场和电场中的自旋过程来完成的，类似于陀螺仪的进动或引力场中的旋转陀螺。电偶极矩改变了这种进动率，尽管改变的幅度很小。如果自旋持续很长时间，这种微小的变化就更容易被检测到。由于分子在阵列中被限制和隔离，时间可能比目前的实验长数千倍。这使得我的测量方案比其他任何实验都要灵敏得多，使我能够以前所未有的精度寻找新的物理。

The Standard Model of particle physics is one of the greatest achievements of modern science. It has been fabulously successful in classifying the fundamental particles and explaining how they behave. Nevertheless, it is widely accepted that the Standard Model is incomplete because it fails to explain several important observations. One prominent example is the excess of matter over antimatter in the universe. The Standard Model predicts almost equal amounts of matter and antimatter, but observations show the universe contains only matter. This contradiction is one of the great unsolved problems in modern physics and a major deficiency of our most fundamental theory.To build a more complete picture of the universe, physicists are striving to reveal what lies beyond the Standard Model. This is an important objective of much of the research being done at gigantic particle accelerators. There is an alternative, and ingenious, way to explore the same problem - measure the shape of an electron. The new forces needed to explain the matter/antimatter imbalance also make electrons slightly non-spherical. This distortion - known as the electric dipole moment - changes the energy of an electron in an electric field, and that tiny change is amplified when the electron is bound to a molecule. I propose to build an apparatus that uses an array of molecules cooled to microkelvin temperatures to make an extremely precise measurement of the electron's shape. With very careful measurements, such table-top experiments enable us to probe energies equal to, or even above, those reached by the particle accelerators. Such marvellous precision has become possible by my recent success in cooling molecules to ultracold temperature. That technique is the foundation of this proposal.My plan is to decelerate a beam of ytterbium monofluoride molecules to rest using the forces exerted by carefully tuned laser light, trap these molecules and cool them to a few microkelvin. Then, I will load them into an array of traps formed by standing waves of light. The array contains millions of individual traps and isolates the molecules from one another, creating a pristine environment for measuring the electron's electric dipole moment. This measurement is done by watching how the spin of the molecules precesses in applied magnetic and electric fields, similar to the precession of a gyroscope or spinning top in a gravitational field. An electric dipole moment changes this precession rate, though only by the tiniest amount. That tiny change is detected more easily if the spin precesses for a long time. Because molecules are confined and isolated in the array, the time can be thousands of times longer than in current experiments. That makes my measurement scheme far more sensitive than any other experiment, allowing me to search for new physics with unprecedented precision.