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

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

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.