CAREER: Developing a High-Dimensional Photonic Quantum Register for the Quantum Internet

The development of quantum networks marks a groundbreaking advancement in how we communicate, compute, and measure the world around us. A key component of these networks is the photonic quantum register—a local quantum memory capable of storing information carried by optical photons. This program aims to create the first scalable solid-state photonic quantum register that can simultaneously store multiple photons within a single nuclear spin. Breakthroughs in the proposed research will lead to ultra-secure communications that are virtually impossible to intercept or hack, a new computing paradigm by allowing multiple quantum computers to collaborate seamlessly, and enhanced precision measurements for applications ranging from navigation to observational astronomy. Furthermore, the program includes an integrated education and outreach plan designed to make quantum science accessible to a wide range of learners, from K-8 students to industry professionals. These efforts will increase the number of people in the STEM field, cultivate a pipeline for the quantum workforce, and empower communities through education. The quantum internet promises fundamentally secure communication, distributed quantum computing, and entanglement-enhanced quantum metrology, each carrying profound technological and societal implications. Central to this vision is the photonic quantum register—an array of long-lived qubits capable of exchanging quantum states with optical photons. Solid-state quantum emitters, particularly their adjacent nuclear spins, offer a scalable solution for constructing these registers due to their seamless integration with on-chip photonic circuits. However, a significant challenge persists: usable nuclear spins are either stochastically distributed around the quantum emitter or, if deterministically integrated, limited to a single spin. This constraint impedes the simultaneous storage of multiple photons in a deterministic way. The proposed program aims to develop the first deterministic solid-state photonic quantum register capable of storing multiple optical photons. We will utilize single Germanium Vacancy (GeV) centers in diamond as quantum memory. The nuclear spin of 9/2 from the 73Ge isotope forms a 10-dimensional qudit, enabling the storage of multiple qubits of quantum information. We will demonstrate the sequential storage and retrieval of multiple photons through a high-fidelity electron-spin-photon interface and controlled nucleus–electron interactions. Additionally, the program includes an education and outreach plan integrated with the research, aimed at creating publicly available resources for teaching and learning quantum optics for broad audiences, ranging from K-8 students to graduate students and industry professionals. 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.