CAREER: Controlling noise in quantum devices with light and sound

虽然掌握新生的量子技术有望实现高性能计算、精密传感和无条件安全通信的新形式，但这些量子设备固有的噪声会降低使其具有非凡性能的特征。对于各种各样的量子器件来说，最有问题的噪声源是由所谓的双能级隧道态（TLSs）产生的。虽然还没有被很好地理解，但tls无处不在——出现在晶体、表面和无序材料中——它们产生的噪音在许多量子技术运行所需的低温下更为剧烈。提出的研究旨在利用TLSs和声波之间的强相互作用来开发新技术来控制和减少这种令人烦恼的噪声源。关键目标涉及工程器件：(1)通过器件几何形状塑造声音如何影响量子器件性能，以及(2)展示如何通过机械波的主动转导来控制量子器件中的噪声。该项目探索了大幅降低TLS产生的噪声的能力，并揭示了目前未知的TLS微观起源，以实现量子技术的实际应用。通过付费的本科生研究机会，关于光物质相互作用的新课程，以及以量子科学为主题的拓展——专注于历史上少数群体的社区——拟议的教育目标旨在解决女性和少数群体在物理科学领域的系统性代表性不足问题，并为代表性不足的群体增加在亚利桑那州新兴技术领域就业的机会。该项目旨在通过操纵声子自由度来证明对双能级隧穿态（TLSs）产生的噪声的控制，并展示如何使用这种控制来提高量子器件的性能。为了实现这些目标，电子、声子和光子器件将被创造出来：(1)由高度受限的膜、波导和谐振器来改变和控制声子的状态密度，预计将极大地改变和重塑TLS噪声的频谱，(2)光可以被利用来传导大振幅机械波，预计将通过“饱和”TLS损耗来降低噪声。脉冲序列测量、微波光谱和一种新型的泵-探针声子光谱将把器件性能与声子操作联系起来。然而，详细的理论与实验对比将阐明声子约束和转导对TLS产生的各种噪声和耗散机制的影响，例如，以机械质量因子的温度依赖性的形式。该项目将展示(1)如何在高度受限的结构阵列中改变TLS噪声，(2)如何使用声子来控制微波域中的TLS噪声，以及(3)如何首次利用声子来提高量子器件性能。总之，这些结果有望确立声子操纵可以延长超导量子比特内电磁量子态的寿命，并可能为量子计算的实际形式和超灵敏的力、旋转、磁场和位移探测器铺平道路。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。

While the mastery of nascent quantum technologies promises new forms of high-performance computing, precision sensing, and unconditionally secure communications, noise inherent to these quantum devices degrades the very features that enable their remarkable properties. The most problematic source of noise for a wide variety of quantum devices is produced by so-called two-level tunneling states (TLSs). While not well understood, TLSs are ubiquitous—appearing in crystals, on surfaces, and within disordered materials—and the noise they produce is more acute at the low temperatures required for the operation of many quantum technologies. The proposed research aims to leverage the strong interaction between TLSs and sound waves to develop new techniques to control and reduce this vexing source of noise. Key objectives involve engineering devices: (1) to shape how sound impacts quantum device performance through device geometry, and (2) to show how noise in quantum devices can be controlled through the active transduction of mechanical waves. This project explores the ability to drastically reduce the noise produced by TLS and shed light on the—currently unknown—microscopic origin of TLSs, toward practical applications of quantum technology. Through paid undergraduate research opportunities, new curricula on light-matter interactions, and quantum science themed outreach—focusing on historically minoritized communities—the proposed educational objectives aim to address systemic underrepresentation of women and minority groups in the physical sciences and increase accessibility to careers in Arizona’s burgeoning technology sector to underrepresented groups.This project aims to demonstrate control of noise produced by two-level tunneling states (TLSs) through the manipulation of phononic degrees of freedom and to show how this control can be used to improve the performance of quantum devices. To achieve these objectives, electronic, phononic and photonic devices will be created: (1) from highly confined membranes, waveguides and resonators that alter and control the phonon density of states, predicted to drastically alter and reshape the spectrum of TLS noise, and (2) where light can be harnessed to transduce large amplitude mechanical waves, expected to reduce noise by “saturating” TLS losses. Pulse sequence measurements, microwave spectroscopy and a new form of pump-probe phonon spectroscopy will connect device performance with phonon manipulation. Whereas, detailed theory-experiment comparison will elucidate the impact of phonon confinement and transduction on various noise and dissipation mechanisms produced by TLS, e.g., in the form of the temperature dependence of the mechanical quality factor. This project will show (1) how TLS noise can be altered in an array of highly confined structures, (2) how phonons can be used to control TLS noise in the microwave domain, and (3) how phonons can be leveraged to improve quantum device performance for the first time. Together, these results are expected to establish that phonon manipulation can extend lifetimes of electromagnetic quantum states within superconducting qubits and may pave the way for practical forms of quantum computing and ultra-sensitive detectors of forces, rotation, magnetic fields and displacement.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.