Collaborative Research: HAYSTAC Quantum Enhanced

加州大学伯克利分校和科罗拉多大学在“Haystac量子增强”的奖励下，参与了世界上寻求发现宇宙暗物质身份的最前沿的实验之一。这项实验寻找一种假想的基本粒子，称为轴子，据预测它极轻，可能是电子质量的万亿分之一，相互作用极弱。该实验的原理是，在强磁场的存在下，轴子可以转化为微波光子，这可以被量子灵敏放大器和接收器探测到。转换过程可以在可调谐的微波腔中共振增强；这些微波腔的研发、生产和运营是加州大学伯克利分校团队的责任。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，也就是实验的所在地。Haystac一直是将量子传感应用于暗物质搜索的世界领先者。在NSF之前的资助下，Haystac是第一个通过一种名为压缩真空态的复杂技术逃避关于放大器不可约噪声的量子力学基本定理--标准量子极限--的暗物质实验。暗物质的发现将构成我们对宇宙学理解的一场革命，并激发一代又一代的年轻学生追求物理科学和工程事业。Haystac还推动了量子信息科学和先进微波概念的突破，并培养了几名进入量子计算和加速器科学领域的博士生。在NSF的资助下，耶鲁-伯克利-科罗拉多在2011年合作设计、建造和运营Haystac(现在约翰·霍普金斯也加入了)，这是一个小型实验，既是开发新的腔体设计和量子增强型光子探测方案的创新试验台，也是在10-50微电动汽车质量范围内获取第一批数据的探索者。在2015年首次使用约瑟夫森参数放大器(JPA)投入使用后，Haystac立即实现了基本上量子限制的操作。在过去的三年里，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限制(SQL)，并建立了大约17微电子伏特的排除限制；这些结果将于2021年2月发表在《自然》杂志上。Haystac是唯一使用压缩态接收器(SSR)的暗物质实验，与LIGO一起是基础物理学领域仅有的两个利用压缩态产生数据的实验之一。在开发量子增强型接收器的同时，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，该团队将完成并分析正在进行的使用当前压缩状态接收器的长期运行，该接收器的扫描速率比第一个SSR进一步提高。然后，伯克利分校将部署一个新的和改进的对称化调谐器设计的腔，另一个长期运行将开始在频率上向上移动，接近最近的理论预测。科罗拉多州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)，应该在这个授权期内完成；尽管目前的SSR在扫描速率方面产生了×2的倍，但这个新的方案预计会产生×15的加速比。科罗拉多州和伯克利将联合在海斯塔克进行整合和调试。伯克利分校将继续研发用于TE模抑制的光子带隙谐振器，超材料谐振器达到更高的频率，并继续缓解异常热噪声的贡献。这些创新中的每一项都极大地增强了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智力优势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.