CAREER: Hybrid Continuous-Discrete Quantum State Generation and Measurement in Silicon Photonics

Nontechnical Description: One of the central principles of quantum mechanics is wave-particle duality: quantum objects can behave both as particles and as waves. In photonic systems, this dual nature of light enables two fundamentally different ways of encoding quantum information. Information can be carried either by individual photons, corresponding to discrete quantum units, or by continuous optical fields that behave like waves. Both approaches are actively explored for the development of fault-tolerant quantum technologies, and each offers distinct advantages but also important limitations. This project explores a hybrid approach that combines these two representations using integrated silicon photonic circuits. The research will use atomic-scale defects in silicon, known as color centers, to control and prepare coherent states of light. These states behave as classical optical fields and are more robust to loss and imperfections than many fragile quantum states. By enabling new ways to generate and measure quantum states, this work could advance technologies for secure communication, precision sensing, and future quantum information systems. Quantum photonics is one of the few platforms that allows quantum phenomena to be observed at room temperature using compact chip-scale devices. The project will also develop the Quantum Photonics Education Toolkit, consisting of integrated photonic chips designed to demonstrate key quantum optics experiments. These devices will be used to train the next generation of quantum engineers and could be shared nationally as accessible educational tools for students entering the rapidly growing field of quantum technologies. Technical Description: This project investigates hybrid continuous-variable (CV) and discrete-variable (DV) quantum photonics in silicon. The objective is to determine when hybrid CV-DV circuits implemented in silicon photonics can outperform purely CV or DV approaches for generating and measuring quantum states. The research combines silicon color centers with integrated photonic circuits fabricated in a silicon photonics foundry to realize scalable spin–photon interfaces and hybrid quantum optical states. The project develops a layout-driven simulation framework, to enable co-design of quantum emitters, photonic circuits, and measurement systems. Using this framework, silicon quantum emitters will be integrated into slow-light photonic structures and characterized using hybrid balanced homodyne detection and photon-number-resolving measurements. These experiments will enable reconstruction of quantum optical states and benchmarking of single-photon fidelity. The project will also investigate remote entanglement protocols based on spin-coherent-state entanglement, enabling scalable generation of hybrid quantum correlations between localized spin qubits and propagating optical states. By combining foundry-scale fabrication, quantum emitter integration, and continuous-variable measurement techniques, the project aims to establish a scalable platform for hybrid quantum state generation and measurement in silicon photonics. 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. NSF Award ID: 2543653 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Walid Redjem | Institution: SUNY at Albany, ALBANY, NY | Award Amount: $588,285 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2543653 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2543653.html