Quantum computers have the potential to solve complex problems much faster than traditional computers, but building systems with millions of interconnected qubits is a daunting challenge. Researchers at MIT and MITRE have developed a quantum-system-on-chip (QSoC) architecture that integrates thousands of interconnected qubits onto a customized integrated circuit. This architecture allows for precise tuning and control of a dense array of qubits and enables the creation of large-scale quantum communication networks by connecting multiple chips using optical networking.
The QSoC architecture utilizes diamond color centers as qubits due to their scalability advantages. These “artifical atoms” can carry quantum information and are compatible with semiconductor fabrication processes. Additionally, diamond color centers have long coherence times and photonic interfaces that allow for remote entanglement with other qubits, overcoming the challenge of qubit inhomogeneity in large systems. To achieve full connectivity, the researchers integrated a large array of diamond color center qubits onto a CMOS chip, allowing for dynamic tuning of qubit frequencies.
The team developed a lock-and-release fabrication process to transfer diamond color center microchiplets onto a CMOS backplane at a large scale. This involved fabricating an array of diamond color center microchiplets, designing nanoscale optical antennas, post-processing a CMOS chip to add microscale sockets, and integrating the two layers using a lock-and-release process. The researchers demonstrated a 500-micron by 500-micron area transfer for an array with 1,024 diamond nanoantennas, showing that the architecture could be further scaled up by using larger diamond arrays and CMOS chips.
Characterizing the system and measuring its performance on a large scale, the researchers built a custom cryo-optical metrology setup to demonstrate over 4,000 qubits on an entire chip that could be tuned to the same frequency while maintaining their spin and optical properties. They also developed a digital twin simulation to connect the experiment with digitized modeling and efficiently implement the architecture. This approach could be applied to other solid-state quantum systems in the future, potentially leading to greater performance and precision with refined materials or control processes.
Overall, the QSoC architecture developed by the team at MIT and MITRE represents a significant advancement in quantum computing hardware technology. By integrating thousands of interconnected qubits onto a single chip, the researchers have demonstrated a scalable and modular platform for quantum communication networks with the potential to solve complex problems more quickly than traditional computers. Through their lock-and-release fabrication process, the team has shown a method for transferring diamond color center microchiplets onto a CMOS backplane at a large scale. This research paves the way for future advancements in quantum computing systems and applications.