July 22, 2026 feature New multiplexing scheme accelerates long-distance quantum communication Ingrid Fadelli Author Sadie Harley Scientific Editor Robert Egan Senior Editor Quantum networks, systems consisting of multiple connected nodes or devices that can transmit quantum information to one another, have the potential to advance future communications. These networks typically leverage entanglement, a quantum phenomenon that prompts two or more distant particles to become highly correlated, so that measuring one instantly affects the state of the other. To ensure that distant particles have become entangled and can transmit quantum states, some quantum scientists try to realize so-called heralded entanglement.

This entails confirmation, from a detectable signal, that entanglement between nodes has been established. Researchers at Tsinghua University and Hefei National Laboratory recently introduced a promising strategy to accelerate the generation of heralded entanglement between multiple ions (i.e., atoms with an electrical charge). Their proposed approach, outlined in a paper published in Physical Review Letters, relies on a so-called multiplexing scheme, a technique to send multiple signals through the same communication channel.

"Our central insight is that the multiplexing scheme employed in this experiment—which executes concurrent excitation attempts analogous to classical protocols—is essential for accelerating heralded entanglement generation between remote matter qubits, a fundamental building block of quantum networks and repeaters," Yunfei Pu, co-senior author of the paper, told Phys.org. "Multiplexing effectively overcomes the round-trip communication latency that severely limits entanglement generation rates." The team's efforts to devise new multiplexing schemes Pu and his colleagues have been developing multiplexing schemes for years, as they believe they will be indispensable for realizing quantum repeaters that can transmit information across distances of more than 1,000 km (620 miles). Their recent study is their latest effort toward this goal.

"Over the past decade, our group extensively investigated multiplexing techniques for neutral-atom and trapped-ion quantum networks, utilizing approaches such as two-dimensional AOD addressing and ion shuttling," said Pu. "Our previous work successfully demonstrated the acceleration of atom-photon entanglement via multiplexing, but multiplexing-enhanced atom-atom entanglement had not yet been realized. In this work, we complete the protocol by demonstrating atom-atom entanglement and achieve highly favorable results, particularly in terms of entanglement fidelity." To demonstrate the potential of their scheme for accelerating atom-atom entanglement, the researchers first built a quantum network consisting of two trapped ions connected by 1.2 km (0.75 miles) of optical fiber.

For their experiment, they used ⁴⁰Ca⁺ ions, positively charged calcium atoms that produce or interact with near-infrared light (i.e., photons with a wavelength of 866 nm). "Although this transition offers a favorable near-infrared (NIR) wavelength, it suffers from a low branching ratio of approximately 6% (probability of emitting the desired photons), leading to significant inefficiency in entanglement attempts," explained Pu.