Axion Dark Matter Experiment at High Frequency (ADMX-HF)

多项天文观测证实，宇宙中约85%的物质不是由已知的基本粒子组成的。破译这种所谓的暗物质的本质对宇宙学、天体物理学和高能粒子物理学具有根本的重要性。最令人兴奋的任务之一是寻找超越粒子物理标准模型的新粒子，该模型描述了所有已知的基本粒子以及它们之间的相互作用。该模型的扩展不仅预测了大质量的新粒子，而且还预测了一些质量非常小的新粒子。后者的候选者是轴子，它被引入来解释量子色动力学中电荷宇称(CP)对称性的破坏是多么微小，该理论描述了强力的作用，例如组成原子核的质子和中子之间的相互作用。事实证明，轴子也是宇宙中暗物质成分的主要候选者。构成我们银河系晕暗物质的轴子可以通过在被磁场渗透的微波腔中转换成窄的射频信号而被探测到。寻找这种信号是这个项目的目标。超导薄膜的研发，以及量子电子学中的压缩态和单光子探测，肯定会产生意想不到的副产品。耶鲁大学的ADMX-HF已经被证明是吸引年轻人才的巨大吸引力，大约一半是女性。这项实验为PI在大纽黑文地区与高中教师的外展活动提供了一个焦点。耶鲁大学皮博迪博物馆是世界上最重要的自然历史博物馆之一。该实验计划在耶鲁皮博迪博物馆建立一个关于暗部门科学的永久展览。这个实验代表了约瑟夫森参数放大器(JPA)在微波腔搜索中的首次使用，以及使用稀释冰箱的操作。ADMX-HF PI制定了提高灵敏度的未来战略，表明对于10 GHz以上，优化搜索将需要从线性放大器过渡到可以避开标准量子极限(SQL)噪声的光子检测方案。该实验的计划包括：a)将系统噪声降低到SQL以下，最初是通过采用基于JPA的压缩真空态接收器；最终，将开发和部署基于超导量子比特的光子探测器系统；b)实现光子带隙(PBG)结构作为传统微波腔的替代；如果成功，它将完全消除TE模式干扰感兴趣的TM模式的丛林，这一直是快速有效的质量覆盖的祸害；以及c)通过两种方法之一来提高腔Q：将薄膜第二类超导体的多层结构融入腔设计中，或者使用基于嵌套介质柱体的分布式布拉格反射器腔。NbTiN是一种第二类超导体，在平面薄膜的制备和表征方面的研发显示出巨大的前景。预计可交付的技术成果是：(A)将搜索的质量范围扩大到12 GHz(50微EV)，以及(B)将功率灵敏度提高5倍，从而接近对DFSZ轴子的灵敏度。这将极大地提高我们在最有希望的质量区域的发现潜力。

Multiple astronomical observations have established that about 85% of the matter in the universe is not made of known elementary particles. Deciphering the nature of this so-called Dark Matter is of fundamental importance to cosmology, astrophysics, and high-energy particle physics. One of the most exciting quests is the search for new particles beyond the Standard Model of Particle Physics, which describes all the known elementary particles and the interactions between them. Extensions of the model predict not only new particles with large masses but also some with very small masses. Such a candidate for the latter is the axion, which has been introduced to explain the smallness of the violation of the Charge-Parity (CP) symmetry in Quantum Chromodynamics, the theory describing the action of the strong force, for example the interactions between protons and neutrons that make up atomic nuclei. The axion turns out to also be a prime candidate for a constituent of the dark matter in the universe. Axions constituting the dark matter of our Milky Way halo may be detected through their conversion into a narrow Radio-Frequency signal in a microwave cavity permeated by a magnetic field. Searching for this signal is the goal of this project.R&D on superconducting thin-films together with squeezed-state and single-photon detection in quantum electronics will certainly produce unanticipated spin-offs. ADMX-HF at Yale, has already proven to be a great attractor for young talent, with roughly half being women. The experiment provides a focal point for the PI's outreach activities with high school teachers in the greater New Haven area. It is planned to establish a permanent exhibit on dark-sector science at the Yale Peabody Museum, one of the foremost natural history museums in the world.This experiment represents the inaugural use of both Josephson Parametric Amplifiers (JPAs) in the microwave cavity search, and operation with a dilution refrigerator. The ADMX-HF PIs have laid out a future strategy for improving sensitivity, showing that, for above 10 GHz, an optimized search will require transitioning from linear amplifiers to photon detection schemes that can evade the Standard Quantum Limit (SQL) noise. The experiment's plans include: a) reducing the system noise below the SQL, initially by incorporating a JPA-based squeezed-vacuum state receiver; eventually, photon detector systems based on superconducting qubits will be developed and deployed; b) implementing a Photonic Band Gap (PBG) structure as an alternative to a traditional microwave cavity; if successful it will completely eliminate the forest of TE modes interfering with the TM mode of interest, which have been a bane to fast and efficient mass coverage; and c) boosting the cavity Q by one of two avenues: Incorporating multilayer structures of thin-film Type-II superconductors into the cavity design, or the use of Distributed Bragg Reflector cavities based on nested dielectric cylinders. R&D on the fabrication and characterization of planar thin-films of NbTiN, a Type-II superconductor is showing great promise. Technical deliverables expected are to (a) extend the mass range of the search to 12 GHz (50 micro eV), and (b) deliver an improvement in power sensitivity by a factor of five, and thus approach sensitivity to DFSZ axions. This will dramatically improve our discovery potential in the most promising mass region.