Researchers from Rochester Institute of Technology (RIT) and national photonic device company AdvR designed and built a quantum chip prototype that the developers say is able to bridge traditional fiber optic networks with quantum computing networks. Using the chip and by better entangling, or integrating, the two communication technologies, quantum computers would be able to process data orders of magnitude faster than current computers and move information across networks more securely. With speed and security coupled with higher sensing power based on quantum mechanics, the technology platform could further improve computing applications for drug development or imaging, said Stefan Preble, principal investigator for RIT’s project team. RIT engineering and science faculty are working to develop quantum chip prototypes and network technology. Courtesy of Elizabeth Lamark. “Quantum has this promise for breakthroughs in many different disciplines, and this comes down to the fundamental level. Quantum behaviors are so different from the classical technologies that we have been designing,” said Preble, a professor of electrical and microelectronic engineering. Preble is also graduate program director of the university’s microsystems engineering doctoral program and a faculty researcher with RIT’s Future Photon Initiative. The basic technology concepts of the project include operation over a wide range of wavelengths — seen and unseen — to produce links between quantum nodes based on atomic, quantum systems, and fiber optic infrastructure. Typically, integrated photonic chips are made from silicon, which has long been the preferred material for chip fabrication. “The problem with silicon is it doesn’t work at the visible wavelengths that we need for quantum nodes that utilize atoms. Silicon can’t solve everything,” Preble said. “With photons, their key advantage is they move at the speed of light, so they are really good at moving information, specifically quantum information, from place to place. That is our focus, to basically connect things together quantum-mechanically.” Faculty researchers are integrating visible light photons in a KTP chip with silicon quantum photonic chips. This type of technology integration will enable a future quantum internet. Courtesy of Stefan Preble. Preble and co-principal investigator Gregory Howland, assistant professor in RIT’s College of Science, are assessing a range of wavelengths and materials. Preble noted that visible wavelength photons do not transmit efficiently over optical fiber. With help from AdvR, the team found potential in a quantum-compatible material capable of interfacing with silicon photonic chips. The material, potassium titanyl phosphate, or KTP, was used to make chips that were then meshed with silicon photonic chips to develop a hybrid quantum photonic integrated circuit. The circuit showed higher sensitivity and functionality than traditional chips. Among the material’s advantages is its ability to be formed into waveguides using traditional lithographic techniques. This enables arrays’ outputs to match the spacing and modal geometry of the silicon photonic integrated circuit input. It also has high resistance to optical damage, said Todd Hawthorne, a member of the project team and an optical engineer with AdvR. “Perhaps mostly importantly for developing a useful optical quantum network, KTP, due to its particular dispersion properties, can, for certain wavelengths and polarizations, produce high-purity, spectrally un-entangled, photon pairs without significant spectral filtering,” Hawthorne said. The next generation of high-purity photons are needed for implementing advanced quantum networking protocols such as entanglement swapping to further develop a long-range quantum network, he said. Further plans during this phase include integrating the KTP waveguide arrays with silicon photonic chips for post-processing of the photon pairs. The project extends through September 2022.