CAREER: Controlling noise in quantum devices with light and sound

尽管对新兴量子技术的掌握有望实现高性能计算、精确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降低了使其具有非凡特性的特性。对于各种各样的量子设备来说，最有问题的噪声源是由所谓的两能级隧道态(TLS)产生的。虽然还不太清楚，但热释光普遍存在--出现在晶体、表面和无序材料中--在许多量子技术运行所需的低温下，它们产生的噪音更加尖锐。这项拟议的研究旨在利用TLS和声波之间的强烈相互作用来开发新的技术来控制和减少这种令人烦恼的噪声源。主要目标涉及工程设备：(1)通过设备几何形状塑造声音如何影响量子设备性能，以及(2)展示如何通过机械波的主动传导来控制量子设备中的噪声。这个项目探索了大幅降低TLS产生的噪声的能力，并阐明了TLS的微观来源--目前尚不清楚--走向量子技术的实际应用。通过有偿的本科生研究机会，关于光-物质相互作用的新课程，以及以量子科学为主题的推广-专注于历史上微区化的社区-拟议的教育目标旨在解决女性和少数群体在物理科学中代表不足的系统性问题，并增加亚利桑那州新兴技术部门对代表不足的群体的职业机会。该项目旨在展示通过操纵声子自由度来控制两能级隧道态(TLS)产生的噪声，并展示如何使用这种控制来提高量子设备的性能。为了实现这些目标，将创造电子、声子和光子器件：(1)利用高度受限的薄膜、波导和谐振器来改变和控制声子态密度，预计将极大地改变和重塑TLS噪声的频谱；以及(2)利用光来传输大幅度的机械波，预计将通过“饱和”TLS损失来降低噪声。脉冲序列测量、微波光谱和一种新形式的泵浦-探测声子光谱将把设备性能与声子操纵联系起来。然而，详细的理论和实验比较将阐明声子限制和转换对TLS产生的各种噪声和耗散机制的影响，例如，以机械品质因子的温度依赖的形式。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)如何使用声子在微波域控制TLS噪声，以及(3)如何利用声子首次提高量子器件的性能。总之，这些结果有望证明，声子操纵可以延长超导量子比特中电磁量子态的寿命，并可能为实际形式的量子计算和力、旋转、磁场和位移的超灵敏探测器铺平道路。这一奖项反映了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。

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.