Collaborative Research: HAYSTAC Quantum Enhanced

在“HAYSTAC量子增强”奖项下，加州伯克利大学和科罗拉多参与了世界上最前沿的实验之一，旨在发现宇宙暗物质的身份。这个实验寻找一种假想的基本粒子，称为轴子，它被预测是非常轻的，也许是电子质量的万亿分之一，并且相互作用非常弱。该实验的原理是，在强磁场的存在下，轴子可以转换为微波光子，这些光子可以被量子敏感放大器和接收器检测到。转换过程可以在可调谐微波腔中共振增强;这些微波腔的研发，生产和操作是加州大学伯克利分校小组的责任。科罗拉多大学的团队开发了量子传感器。参与实验的其他机构是约翰霍普金斯大学和耶鲁大学。HAYSTAC一直是量子传感应用于暗物质搜索的世界领导者。在之前的NSF资助下，HAYSTAC是第一个通过一种称为压缩真空态的复杂技术来逃避关于放大器不可约噪声的量子力学基本定理的暗物质实验，标准量子极限。暗物质的发现将构成我们对宇宙学理解的一场革命，并激励一代又一代的年轻学生追求物理科学和工程的职业生涯。HAYSTAC也是量子信息科学和先进微波概念突破的推动者，并培养了多名博士。在NSF的资助下，耶鲁大学-伯克利分校-科罗拉多大学于2011年合作设计、建造和运营HAYSTAC。（现在加入了约翰霍普金斯），一个小型实验，既作为创新试验台，以开发新的腔设计和量子增强光子探测方案，并作为在10-50微电子伏特质量范围内获取第一数据的探路者。在2015年首次使用约瑟夫森参量放大器（JPA）进行调试后，HAYSTAC实现了基本的量子限制操作。在过去的三年里，该合作成功地实现了一个双JPA压缩真空态接收器，完全绕过了标准量子极限（SQL），并建立了约17微电子伏特的排阻极限;这些结果于2021年2月发表在《自然》杂志上。HAYSTAC是唯一一个使用压缩态接收器（SSR）的暗物质实验，并且沿着LIGO是基础物理世界中仅有的两个利用压缩态进行数据生产的实验之一。与量子增强接收器的开发并行，该合作在微波谐振器方面也取得了类似的进展。根据这一提议，该团队将使用当前的压缩态接收器完成并分析正在进行的长期运行，该接收器的扫描速率从第一个SSR进一步提高。然后，伯克利将部署一个新的和改进的对称调谐器设计腔，另一个长期运行将开始向上移动的频率向最近的理论预测。科罗拉多将开发和测试他们的腔纠缠和状态交换概念的原型（发表在《物理评论X量子》上），这应该在本资助期内完成;而目前的SSR产生了×2的扫描速率，这个新方案预计将产生×15的加速。科罗拉多和伯克利将共同进行HAYSTAC的集成和调试。伯克利将继续研发用于TE模式抑制的光子带隙谐振器，超材料谐振器，以达到更高的频率，并继续减轻异常热噪声的贡献。每一项创新都极大地增强了HAYSTAC的发现潜力。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Under the award "HAYSTAC Quantum Enhanced", the University of California Berkeley and the University of Colorado participate in one of the forefront experiments in the world seeking to discover the identity of the dark matter of the universe. This experiment searches for a hypothetical elementary particle, called the axion, which is predicted to be extremely light, perhaps a trillionth of the mass of an electron, and extremely weakly interacting. The principle of the experiment is that in the presence of a strong magnetic field, axions can convert to microwave photons, which can be detected by quantum-sensitive amplifiers and receivers. The conversion process can be resonantly enhanced in a tunable microwave cavity; the R&D, production and operation of these microwave cavities is the responsibility of the UC Berkeley group. The University of Colorado team develops the quantum sensors. The other institutions involved are Johns Hopkins University and Yale University, where the experiment is sited. HAYSTAC has been the world leader in the application of quantum sensing to dark matter searches. Under previous NSF funding, HAYSTAC was the first dark matter experiment to evade a fundamental theorem of quantum mechanics on the irreducible noise of amplifiers, the Standard Quantum Limit, by a sophisticated technique known as squeezed-vacuum states. Discovery of dark matter would constitute a revolution in our understanding of cosmology, and excite generations of young students to pursue careers in physical science and engineering. HAYSTAC has also been a driver for breakthroughs in quantum information science, and advanced microwave concepts, and has trained several Ph.D. students who have gone on to careers in the fields of quantum computing and accelerator science.Under NSF funding, a Yale-Berkeley-Colorado collaboration came together in 2011 to design, build and operate HAYSTAC (now joined by Johns Hopkins), a small experiment serving both as an innovation test-bed to develop new cavity designs and quantum-enhanced photon detection schemes, and as a pathfinder to take first data in the 10–50 micro-eV mass range. Immediately upon commissioning in 2015 with the first-ever use of a Josephson Parametric Amplifier (JPA), HAYSTAC achieved essentially quantum-limited operation. In the past three years, the collaboration successfully implemented a two-JPA squeezed-vacuum state receiver, circumventing the Standard Quantum Limit (SQL) entirely and establishing an exclusion limit around 17 micro-eV; these results being published in Nature in February 2021. HAYSTAC is the only dark matter experiment to employ a squeezed-state receiver (SSR), and along with LIGO one of only two experiments exploiting squeezed states for data production in the world of fundamental physics. In parallel with the development of quantum-enhanced receivers, the collaboration has pursued similar advances in microwave resonators. Under this proposal, the team will complete and analyze the ongoing long run with the current squeezed state receiver, which is operating with a scan rate further improved from the first SSR. Berkeley will then deploy a new and improved symmetrized-tuner design cavity, and another long run will commence to move upwards in frequency toward a recent theoretical prediction. Colorado will develop and test a prototype of their cavity entanglement and state-swapping concept (published in Physical Review X Quantum), which should be complete within this grant period; whereas the current SSR yielded a factor of ×2 in scan rate, this new scheme is expected to produce a ×15 speedup. Colorado and Berkeley will jointly carry out the integration and commissioning in HAYSTAC. Berkeley will continue R&D on Photonic Band Gap resonators for TE-mode suppression, metamaterial resonators to reach much higher frequencies, and continued mitigation of the anomalous thermal noise contribution. Each of these innovations dramatically enhance the discovery potential of HAYSTAC.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.