CAREER: Quantum silicon phononics: Harnessing long-lived phonons for memories and interconnects

在过去的二十年中，量子技术稳步发展，有望在计算，通信和传感方面广泛应用解决方案。到目前为止，为量子技术开发物理平台的大部分努力都集中在作为量子信息载体的光子和用于存储和处理量子信息的原子和固态量子比特上。声子是固态材料振动中的能量量子，最近成为量子技术的一种可行资源。由于声子能够与广泛的系统相互作用，声子可以作为互连，将量子信号从量子计算机可能运行的电域传递到光纤实现长距离量子通信的光域。此外，在纳米工程器件中，声子可以很好地与环境隔离，有可能提供存储量子态的存储元件。将这些物理特性发展为实验能力，并随后实现技术优势，需要将机械设备与其他量子硬件平台连接起来的方法。该项目旨在为长寿命的机械谐振器创建可扩展的、芯片级的光学和电子量子接口。此外，该项目旨在通过在电子、光学和机械量子设备之间创建量子纠缠的实验演示中使用它们来评估开发的接口的实际效益。由单晶硅制成的ghz频率声学谐振器具有极低损耗（在低温下达到500亿质量因子）和易于与电信波段光子接口的独特特性。然而，虽然声子的量子操作之前已经通过压电耦合超导量子比特得到了证明，但硅中压电的缺失阻止了与量子比特的直接集成。该项目旨在通过在单片绝缘体上硅平台上开发ghz频率机械谐振器与超导量子比特和腔光力学系统机电耦合的新机制来克服这一挑战。为了实现这一目标，该项目将开发基于声子晶体的静电换能器和基于无序超导体中动态电感的高阻抗微波腔。集成这些组件，PI的目标是实现具有transmon量子比特的机电谐振器的全量子控制，并演示微波光子到光子的电光力学转换。在这种方法中，无损耗压电材料和对耐光超导体的依赖有望转化为异常长的机械寿命和微波到光频率转换效率的数量级提高。该项目旨在利用这些改进，在由transmon量子位元（充当处理器）、声子晶体谐振器（存储元件）和电信波段光子（互连）组成的实验室规模混合网络中演示量子纠缠操作。展示这种混合量子网络对于未来的实际应用至关重要，可以提供对量子计算云、分布式量子计算和量子传感的安全远程访问。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。

Over the last two decades, quantum technologies have progressed steadily, promising solutions to a wide range of applications in computation, communication, and sensing. The bulk of efforts in developing physical platforms for quantum technologies has so far focused on photons as carriers of quantum information and atomic and solid-state qubits for storing and processing quantum information. Phonons, the quanta of energy in vibrations in solid-state materials, have recently emerged as a viable resource for quantum technologies. Due to their ability to interact with a wide range of systems, phonons can serve as interconnects to pass quantum signals from the electrical domain, where quantum computers are likely to operate, to the optical domain, where optical fibers enable long-distance quantum communication. Additionally, phonons can be well isolated from their environments in nano-engineered devices, potentially providing memory elements for storing quantum states. Developing these physical properties into experimental capabilities and, subsequently, a technological advantage requires methods of interfacing mechanical devices with other quantum hardware platforms. This project aims to create scalable, chip-scale optical and electrical quantum interfaces to long-lived mechanical resonators. Furthermore, the project aims to assess the practical benefits of the developed interfaces by using them in experimental demonstrations that create quantum entanglement between electrical, optical, and mechanical quantum devices.GHz-frequency acoustic resonators made from single-crystal silicon offer the unique properties of exceptionally low loss (reaching 50-billion quality factors at low temperatures) and the ease of interfacing with telecom-band optical photons. However, while quantum manipulations of phonons have been previously demonstrated with piezoelectric coupling to superconducting qubits, the absence of piezoelectricity in silicon forbids direct integration with qubits. This project aims to overcome this challenge by developing new mechanisms for electromechanical coupling of GHz-frequency mechanical resonators with superconducting qubits and cavity optomechanical systems in a monolithic silicon-on-insulator platform. To achieve this goal, the project will develop electrostatic transducers based on phononic crystals and high-impedance microwave cavities based on kinetic inductance in disordered superconductors. Integrating these components, the PI aims to realize full quantum control of electromechanical resonators with transmon qubits and demonstrate electro-optomechanical conversion of microwave photons to optical photons. The absence of lossy piezoelectric materials and the reliance on light-resistant superconductors in this approach is expected to translate to exceptionally long mechanical lifetimes and orders-of-magnitude improvement in the efficiency of microwave-to-optical frequency conversion. The project aims to take benefit of these improvements for demonstrating quantum entangling operations in a lab-scale hybrid network made from transmon qubits (acting as processors), phononic crystal resonators (memory elements), and telecommunication band photons (interconnects). Demonstrating such a hybrid quantum network would be essential for future real-world applications in providing secure remote access to quantum computing clouds, distributed quantum computing, and quantum-enabled sensing.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.