Carnegie Mellon University Team Selected for DARPA HARQ Program

A research team from the Department of Electrical and Computer Engineering at Carnegie Mellon University (CMU) has been selected for funding under DARPA’s Heterogeneous Architectures for Quantum (HARQ) program. The team is led by Qing Li, associate professor of electrical and computer engineering and principal investigator, along with Gianluca Piazza, the STMicroelectronics Professor of Electrical and Computer Engineering, serving as co-principal investigator.

Today’s quantum computing systems largely rely on a single type of qubit to perform all computational tasks. The HARQ program, led by program manager Justin Cohen, aims to move beyond this paradigm by enabling heterogeneous quantum architectures that integrate multiple types of qubits within a single system. By combining advances in photonic integration, quantum interconnects, and circuit design, the program seeks to address key challenges in scalability and performance that limit current quantum technologies.

As part of the program, the CMU team will develop a scalable solution for optical-to-optical frequency conversion, an essential capability for linking disparate quantum systems (TA2, Track B). Such a converter must preserve fragile quantum states with high fidelity while supporting a wide wavelength range from 370 to 1550 nanometers, all under practical operating conditions with minimal system reconfiguration.

“Despite its importance, no existing technology fully meets these requirements,” explains Li. “Current approaches are typically restricted to fixed wavelength pairs and lack the flexibility needed for heterogeneous systems. Achieving near-unity conversion efficiency while suppressing noise remains a significant challenge, further complicated by practical limitations in pump laser technology, including wavelength availability, power, tunability, and cost.”

To address these challenges, the CMU team will develop a novel device architecture based on a highly nonlinear, quantum-grade silicon carbide integrated photonics platform. This approach is designed to simultaneously achieve high single-photon conversion efficiency, large signal-to-noise ratio, broad operational bandwidth, and ultra-low optical pump power.

The effort builds on the team’s extensive experience with wide-bandgap materials. Since 2019, Li’s group has pioneered the development of the 4H-silicon-carbide-on-insulator photonics platform, supported by previous DARPA funding for nonlinear optical technologies. Their work has demonstrated key advantages of 4H-SiC over more established materials such as silicon and silicon nitride, including stronger third-order optical nonlinearity, higher thermal conductivity, and excellent optomechanical performance.

The project also leverages Piazza’s expertise in piezoelectric materials, particularly aluminum nitride, and its low-loss integration with silicon carbide, enabling new opportunities for hybrid photonic and electromechanical systems.

“We are excited to be part of the HARQ program,” says Li. “We look forward to collaborating with other performers to advance integrated, heterogeneous quantum systems.”