CAREER: Generation and detection of large-scale quantum entanglement on an integrated photonic chip

量子信息和量子计算早已确立了革命性的承诺，比如将困难的计算以指数级加速到几乎不可能的计算。通过对原子和分子进行建模，它们可以直接应用于解决一些社会上最大的挑战，例如肥料生产的固氮、室温超导和制药。人们已经认识到，要实现实用、通用和容错的量子计算，需要数百万到数十亿个原始量子比特。然而，目前还没有建立这种高度可扩展的量子系统的既定范例。因此，在大尺度下实现可扩展性和保持高相干性是量子信息处理的两个核心挑战。许多现有的量子系统，如超导量子比特和捕获离子量子比特，由于缺乏多路复用，只能逐个量子位扩展：必须再制造N个物理结构才能增加N个量子位。因此，由于复合产率的力量，进一步增加量子位的数量是指数级的挑战。量子光学提供了一个很有前途的替代方案，这要归功于它在光谱、时间和空间领域的光子复用能力，这意味着只需几个设备就可以在频率、时间或空间领域产生大量的量子模式。为了达到下一步，量子集成技术必须成为现实，即集成大量的光子元件来处理大量的量子模式。本提案旨在开发大规模多方纠缠产生的方法，其中所有关键要素，包括纠缠产生和检测，将集成在同一芯片上。所提出的工作可以在量子计算、网络和传感领域开辟新的途径。本研究的目标是开发利用集成光子电路产生大规模多部纠缠态的方法。该方法基于高q光学微谐振器，其中数百个频率由自由频谱范围分隔的经度光学模式将作为频率复用量子模式，通过连续变量方法编码量子信息。微谐振腔中的克尔参量过程和不同微谐振腔之间的量子干涉将产生量子模式之间的无条件纠缠。为了实现“片上量子实验”，将具有高量子效率的平衡光电二极管与纠缠产生芯片异质集成，这将最小化量子态产生和检测之间的多余损耗和相位波动，以保持纠缠质量。该项目不仅将在集成光子电路产生的多方纠缠的规模和质量上实现巨大飞跃，更重要的是，它将在连续变量量子光学的小型化和适用性方面迈出重要一步，推动量子计算、通信和传感领域的应用。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。

Quantum information and quantum computing have long established revolutionary promises, such as exponential speedup of difficult to near-impossible computations. They can be directly applied to attack some of society’s biggest challenges through modeling atoms and molecules, such as nitrogen fixation for fertilizer production, room-temperature superconductivity, and pharmaceuticals. It has been recognized that millions to billions of raw qubits are required to realize practical, universal, and fault-tolerant quantum computing. Yet there exists no established paradigm for building such highly scalable quantum systems. Therefore, achieving scalability and maintaining high coherence at a large scale are two of the central challenges to quantum information processing. Many existing quantum systems, like superconducting qubits and trapped ion qubits, are scaled up qubit by qubit due to the lack of multiplexing: one has to fabricate N more physical structures to add N more qubits. Thus, to further increase the number of qubits is exponentially challenging because of the power of the compound yield rate. Quantum optics provides a promising alternative thanks to its capability of photonic multiplexing in spectral, temporal, and spatial domains, meaning that a large number of quantum modes in frequency, time, or spatial domain can be generated with just a few devices. In order to reach the next step, quantum-integrated technology must become a reality, where a massive number of photonic elements are integrated to process the large number of quantum modes. This proposal aims to develop methods for large-scale multipartite entanglement generation, where all critical elements, including entanglement generation and detection, will be integrated on the same chip. The proposed work can open up new avenues in the fields of quantum computing, networking, and sensing.The proposed effort aims to develop methods to generate large-scale multipartite entanglement states with integrated photonic circuits. The approach is based on high-Q optical microresonators, where hundreds of longitude optical modes with their frequencies separated by free-spectral-range will serve as frequency multiplexed quantum modes to encode quantum information through the continuous-variable approach. Unconditional entanglement among the quantum modes will be created by the Kerr parametric process in microresonators and quantum interference among different microresonators. To pursue “quantum experiment on a chip,” balanced photodiodes with high quantum efficiency will be heterogeneously integrated with the entanglement generation chip, which will minimize excess loss and phase fluctuation between quantum state generation and detection to preserve the quality of entanglement. This project will not only create a quantum leap in the scale and quality of multipartite entanglement generated with integrated photonic circuits, but more importantly, it will be a significant step forward in the miniaturization and applicability of continuous-variable quantum optics and push the state-of-art for applications in quantum computing, communication, and 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.