New Electrically Powered Entangled Light Source on a Chip

Quantum technologies are cutting-edge systems that can process, transfer, or store information leveraging quantum mechanical effects, particularly a phenomenon known as quantum entanglement. Entanglement entails a correlation between two or more distant particles, whereby measuring the state of one also defines the state of the others. In recent years, quantum physicists and engineers have been trying to realize devices that operate leveraging the entanglement between individual particles of light (i.e., photons). The reliable operation of these devices relies on so-called entangled photon sources (EPSs), components that can generate entangled pairs of photons. Researchers at University of Science and Technology of China, Jinan Institute of Quantum Technology, CAS Institute of Semiconductors and other institutes recently realized a new EPS integrated onto a single photonic chip, which can generate entangled photons via an electrically powered laser. Their study is published in Physical Review Letters. "Our research was motivated by the growing demand for compact, high-performance EPSs that can be integrated into practical quantum systems," Qiang Zhang, co-senior author of the paper, told Phys.org. "Traditional sources often rely on bulky external pump lasers, which limit scalability and stability. In this work, we aimed to develop an electrically pumped, chip scale EPS that combines high brightness and broad bandwidth within a fully integrated platform." The reliable entanglement of photons on-chip Zhang and his colleagues have been trying to develop an electrically powered EPS that could be integrated on-chip, enabling the realization of highly performing quantum photonic devices. These devices could be used to implement quantum key distribution protocols and other quantum protocols on a large scale, opening new possibilities for quantum communications, sensing and metrology. "We integrated a distributed feedback (DFB) laser chip with a thin-film lithium niobate (TFLN) photonic chip, which is the key to realizing an electrically pumped device," explained Zhang. "The TFLN chip integrates several on-chip components: dual-channel periodically poled lithium niobate (PPLN) waveguides that generate photon pairs via the nonlinear process of spontaneous parametric down conversion (SPDC), a multimode interference (MMI) beam splitter that evenly divides the pump light, and a polarization rotator combiner (PRC) that rotates the polarization of photons from one waveguide and then combines them with the other waveguide to realize interference, thereby generating polarization-entangled states." Notably, the team's integration strategy does not require any external lasers or other bulky equipment. This makes the resulting EPS more compact and stable than many other previously proposed systems. "Our integrated, electrically driven architecture enables scalable and high-performance implementations of quantum protocols such as quantum key distribution via wavelength division multiplexing, satellite-based quantum communication, and entanglement-based quantum metrology," said Zhang. "Our on-chip EPS simultaneously delivers high brightness (4.5×1010 pairs/s/mW) and broad bandwidth (73 nm). By integrating the pump laser directly on-chip, we eliminate the need for a bulky external laser system, which not only enhances the compactness and scalability of the source but also significantly improves its stability and portability." Fueling the development of quantum photonic systems Many EPSs introduced in the past require the precise alignment of optical components and only work in highly controlled laboratory settings. In contrast, the on-chip EPS created by this research team can operate reliably at room temperature and could be easier to deploy in real-world settings. "The source's high brightness and wide bandwidth make it suitable for wavelength-division-multiplexed quantum key distribution," said Zhang. "Furthermore, its integrated architecture provides a stable and miniaturized platform that could support future quantum networks, distributed quantum processors, and satellite-based quantum links, accelerating the transition of quantum technologies from lab to field." The new EPS introduced by Zhang and his colleagues could soon be improved further and used to develop various quantum photonic devices. The researchers are now trying to optimize the performance of the source on-chip, to further boost the visibility, bandwidth and brightness of generated photons. "We also plan to improve the scalability and multi-channel capability of the system by exploring the generation of hyperentanglement across multiple degrees of freedom such as polarization, frequency and path," added Zhang. "Thirdly, an effort will be dedicated to system packaging and engineering, developing robust and portable modules that ensure long-term stability and ease of use in field applications." © 2026 Science X Network