An anonymous reader writes: When a team of Chinese scientists beamed entangled photons from the nation’s Micius satellite to conduct the world’s first quantum-secured video call in 2017, experts declared that China had taken the lead in quantum communications. New research suggests that lead has extended to quantum computing as well. In three preprint papers posted on arXiv.org last month, physicists at the University of Science and Technology of China (USTC) reported critical advances in both quantum communication and quantum computing. In one of the studies, researchers used nanometer-scale semiconductors called quantum dots to reliably transmit single photons — an essential resource for any quantum network — over 300 kilometers of fiber, well over 100 times farther than previous attempts. In another, scientists improved their photonic quantum computer from 76 detected photons to 113, a dramatic upgrade to its “quantum advantage,” or how much faster it is than classical computers at one specific task. The third paper introduced Zuchongzhi, made of 66 superconducting qubits, and performed a problem with 56 of them — a figure similar to the 53 qubits used in Google’s quantum computer Sycamore, which set a performance record in 2019.
All three achievements are world-leading, but Zuchongzhi in particular has scientists talking because it is the first corroboration of Google’s landmark 2019 result. “I’m very pleased that someone has reproduced the experiment and shown that it works properly,” says John Martinis, a former Google researcher who led the effort to build Sycamore. “That’s really good for the field, that superconducting qubits are a stable platform where you can really build these machines.” Quantum computers and quantum communication are nascent technologies. None of this research is likely to be of practical use for many years to come. But the geopolitical stakes of quantum technology are high: full-fledged quantum networks could provide unhackable channels of communication, and a powerful quantum computer could theoretically break much of the encryption currently used to secure e-mails and Internet transactions.
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