Collaborative Research: HAYSTAC Quantum Enhanced

在“HAYSTAC量子增强”奖下，加州大学伯克利分校和科罗拉多大学参与了世界上寻求发现宇宙暗物质身份的前沿实验之一。这个实验寻找一种假想的基本粒子，叫做轴子，据预测它非常轻，也许只有电子质量的万亿分之一，而且相互作用非常弱。该实验的原理是，在强磁场的存在下，轴子可以转化为微波光子，可以被量子敏感放大器和接收器探测到。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包括约翰霍普金斯大学和耶鲁大学。在将量子传感应用于暗物质搜索方面，HAYSTAC一直处于世界领先地位。在之前的NSF资助下，HAYSTAC是第一个暗物质实验，通过一种被称为压缩真空态的复杂技术，避开了关于放大器不可还原噪声的量子力学基本定理，即标准量子极限。暗物质的发现将对我们对宇宙学的理解构成一场革命，并激发一代又一代年轻学生从事物理科学和工程方面的职业。HAYSTAC还推动了量子信息科学和先进微波概念的突破，并培养了几名在量子计算和加速器科学领域从事职业的博士生。在美国国家科学基金会的资助下，耶鲁-伯克利-科罗拉多合作于2011年共同设计，建造和运营HAYSTAC（现在约翰霍普金斯大学也加入了HAYSTAC），这是一个小型实验，既是开发新腔设计和量子增强光子探测方案的创新试验台，也是在10-50微电子伏特质量范围内获取第一批数据的探路者。在2015年首次使用Josephson参数放大器（JPA）进行调试后，HAYSTAC立即实现了基本的量子限制操作。在过去的三年中，该合作成功地实现了一个双jpa压缩真空状态接收器，完全绕过了标准量子极限（SQL），并建立了17 micro-eV左右的排除极限；这些研究结果将于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，它与LIGO一起是基础物理世界中仅有的两个利用压缩态来产生数据的实验之一。在开发量子增强接收器的同时，该合作也在微波谐振器方面取得了类似的进展。根据该提案，该团队将使用当前压缩状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比第一个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朝着最近的理论预测的频率向上移动。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），这应该在这个资助期内完成；目前的SSR在扫描速率上的系数为×2，而这种新方案预计将产生×15的加速。科罗拉多和伯克利将共同在HAYSTAC进行集成和调试。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。该奖项反映了美国国家科学基金会的法定使命，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.