Collaborative Research: Quantum acoustics for optomechanical transduction and entanglement of solid-state spin qubits

未来的量子计算机将需要利用不同物理类型的量子比特，这些量子比特需要高保真度和高效率地相互通信和转换。虽然光子是量子通信的理想选择，但不同的量子比特系统与频率范围大不相同的光子耦合。固体材料中由机械波产生的应变场是一种很有前途的方法，可以实现与大范围量子比特的耦合，理论上效率很高。声波的传播速度比光子低5个数量级，是多个量子位之间量子互连的理想选择。该项目开发的量子声学技术以及与nv缺陷中心量子比特的集成是迈向芯片级混合多量子比特系统的重要第一步。提出的研究既解决了困扰固态光学量子比特的频率不均匀性问题，又探索了机械模式与自旋量子比特强耦合的前沿。该项目将从先前的离散系统研究中取得重大进展，实现一个单片量子系统，包括波导，光学和声学腔，以及与量子位直接接口的声学换能器，所有这些都集成在一个新的材料平台上。该方法为实现基于光子和声子相互连接的混合固态量子比特的集成量子计算系统提供了一条途径。该研究利用声学MEMS技术的巨大技术发展，将其推进到量子体制，其潜在的结果可能会影响量子信息科学和经典通信的微波光子学。教育和外展活动旨在提高代表性不足群体学生的参与度，改善STEM劳动力的多样性，并包括先进量子计算和K-12科学外展项目的课程开发，并提供公开的在线课程。技术摘要：本项目旨在开发一种新型集成量子声学器件平台，用于基于金刚石缺陷中心的固态自旋量子比特的光力学转导和量子态操纵。该集成器件将建立在晶体金刚石上的高性能磷化镓（GaP）非均质材料平台上。该平台独特地利用压电GaP层实现光波导和声波产生和引导的双重功能，从而极大地增强了声光相互作用。这一努力将包括三个主要方面。第一阶段将实现基于缺陷中心的集成声光移频器（AOFS），解决量子比特的光频不均匀性问题。AOFS可以在±3GHz范围内自由实现量子比特光子的单边带、载波抑制频移，效率优于80%。第二个推力将研究流动声波与整体和单个缺陷中心的耦合。声学耦合强度将得到增强，达到强耦合状态，实现对量子比特状态的时变控制。最终推力将实现嵌入单个缺陷中心的高q腔内声模的强耦合。利用声学模式实现量子比特的量子态操纵和量子纠缠。在强耦合环境下，nv中心与腔声模式耦合的系综以及在强耦合环境下的新物理效应将被探索。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。

Future quantum computers will need to utilize different physical types of qubits that need to communicate and convert between each other with high fidelity and high efficiency. While photons are ideal for quantum communication, different qubit systems couple to photons of vastly different frequency ranges. The strain field generated by the mechanical wave in a solid-state material is a promising approach to enable coupling with a broad range of qubits with theoretically high efficiency. With a traveling velocity of five orders of magnitude lower than photons, acoustic waves are ideal for quantum interconnect between multiple qubits. The quantum acoustic technology developed in this project and the integration with NV-defect center qubits is an essential first step toward a chip-scale hybrid, multiple qubit systems. The proposed research both addresses the imminent issue of frequency inhomogeneity that has been plaguing solid-state optical qubits and explores the frontier of strong coupling of mechanical modes with spin qubits. The project will make significant advances from previous studies of discrete systems to realizing a monolithic quantum system that includes waveguides, optical and acoustic cavities, and acoustic transducers to directly interface with qubits, all integrated on a novel material platform. The approach offers a path to the realization of the integrated quantum computing system based on hybrid solid-state qubits interconnected with photons and phonons. The research leverages the tremendous technological development in the acoustic MEMS technology and advances it to the quantum regime, with the potential outcome that can impact both quantum information science and microwave photonics for classical communication. Education and outreach activities aim to increase the participation of students from underrepresented groups and improve the diversity of the STEM workforce and include course development in advanced quantum computing and K-12 science outreach programs with publicly accessible online courses. Technical Abstract:The project aims to develop a novel integrated quantum acoustic device platform for optomechanical transduction and quantum state manipulation of solid-state spin qubits based on defect centers in diamond. The integrated devices will be built on the high-performance heterogeneous material platform of gallium phosphide (GaP) on the crystalline diamond. The platform uniquely utilizes the layer of piezoelectric GaP for the dual functions of optical waveguiding and acoustic wave generation and guiding, thereby to achieve tremendously enhanced acousto-optic interaction. The effort will include three main thrusts. The first thrust will realize integrated acousto-optic frequency shifter (AOFS) to address the optical frequency inhomogeneity problem of qubits based on defect centers. AOFS can achieve single-sideband, carrier-suppressed frequency shift of photons from qubits freely over a range of ±3GHz and with an efficiency better than 80%. The second thrust will investigate the coupling of itinerant acoustic waves to ensembles and single defect centers. The acoustic coupling strength will be enhanced to reach the strong coupling regime and realize time-dependent control over the states of the qubits. The final thrust will realize the strong coupling of acoustic modes confined in a high-Q cavity with single defect centers embedded therein. Quantum state manipulation and quantum entanglement of the qubits by utilizing the acoustic mode will be achieved. Ensembles of NV-centers coupled to the cavity acoustic mode in the strong-coupling regime and novel physics effects in this regime will be explored.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.