In pursuit of a fast and efficient source of entangled photon pairs necessary for quantum computing and ultrafast communications, researchers from Stevens Institute of Technology have developed a chip-based source capable of producing entangled photon pairs 100× more efficiently than previously possible. Traditional methods trap light in meticulously crafted nanoscale microcavities; light moving through the cavity causes individual photons to resonate and split into entangled pairs. The problem is that these systems are inefficient, requiring pulses of incoming laser light composed of hundreds of millions of photons before a single entangled pair is created. Yuping Huang and his colleagues at Stevens Institute of Technology demonstrated a quantum circuit that can readily be integrated with other optical components, paving the way for high-speed, reconfigurable, and multifaceted quantum devices. Courtesy of QuEST Lab, Stevens Institute of Technology. The method developed by Yuping Huang, Gallagher Associate Professor of Physics and director of the Center for Quantum Science and Engineering, and his colleagues allows for the creation of tens of millions of entangled photon pairs per second from a single microwatt-powered laser beam. “It’s long been suspected that this was possible in theory, but we’re the first to show it in practice,” Huang said. Huang built on his own research efforts with graduate students Zhaohui Ma and Jiayang Chen to develop very high-quality microcavities into flakes of lithium niobate crystal. The cavities exhibit the shape of a racetrack and internally reflect photons with little loss of energy. This allows the light to circulate for longer and interact with greater efficiency, due to influences including temperature. The researchers have begun refinements to their process and say they expect to achieve a quantum optics system that can turn a single incoming photon into an entangled pair of outgoing photons with virtually no wasted energy. “It’s definitely achievable,” Chen said. “At this point, we just need incremental improvements.” In the interim, the team intends to continue furthering its technology and searching for ways to use its device to drive logic gates and other quantum computing or communication components. “Because this technology is already chip-based, we’re ready to start scaling up by integrating other passive or active optical components,” Huang explained. According to Huang, the ultimate goal is to make quantum devices so efficient and cheap to operate that they can be integrated into mainstream electronic devices. “We want to bring quantum technology out of the lab, so that it can benefit every single one of us,” Huang said. “Someday soon we want kids to have quantum laptops in their backpacks, and we’re pushing hard to make that a reality.” The research was published in Physical Review Letters (https://arxiv.org/abs/2010.04242).