China stabilizes 10,000-atom quantum state
- University of Science and Technology of China researchers reported a minute-scale Schrödinger-cat state in trapped ytterbium-173 atoms, turning a viral claim into a documented result. - The team kept the cat state coherent for 1.4×10^3 seconds, about 23 minutes, using spin-5/2 ytterbium nuclei in an optical lattice. - The result targets quantum sensing near the Heisenberg limit, not a 10,000-qubit computer. (nature.com)
A quantum superposition is a state that acts like a coin spinning in the air, not yet settled as heads or tails. In this experiment, Chinese researchers kept that kind of “both at once” state alive for about 23 minutes in trapped ytterbium atoms. (nature.com) (arxiv.org) The work came from Y. A. Yang, W.-T. Luo, J.-L. Zhang, S.-Z. Wang, Chang-Ling Zou, Tian Xia and Z.-T. Lu at the University of Science and Technology of China and affiliated Hefei labs. Nature Photonics published the paper in late 2024 after the team first posted it on arXiv on October 12, 2024. (nature.com) (arxiv.org) The researchers used optically trapped ytterbium-173, an isotope whose nucleus has spin 5/2, giving it several internal orientations to work with. They created a Schrödinger-cat state as a superposition of two oppositely directed, furthest-apart spin states. (nature.com) (arxiv.org) The key number was a coherence time of 1.4(1) × 10^3 seconds, which is about 23 minutes and 20 seconds. Coherence time is the interval before outside noise scrambles the quantum phase that makes interference and precision measurement possible. (nature.com) (thequantuminsider.com) They got there by shielding the state inside what physicists call a decoherence-free subspace, which works like putting a microphone in a noise-canceling booth. In this case, that protection suppressed inhomogeneous light shifts from the optical lattice that held the atoms in place. (nature.com) (arxiv.org) This was not a report of a 10,000-qubit processor doing computation. The paper describes long-lived nonclassical states in optically trapped ytterbium-173 atoms for quantum metrology, especially magnetic-field sensing with Ramsey interferometry. (nature.com) (en.ustc.edu.cn) Quantum metrology is the branch of physics that uses fragile quantum effects to measure fields and time more precisely than ordinary sensors can. The USTC team said its magnetic-field measurements approached the Heisenberg limit, the benchmark that sets the best possible scaling of precision with quantum resources. (nature.com) (arxiv.org) The viral framing around “10,000 atoms” appears to compress or blur the published result. The Nature Photonics abstract and the arXiv abstract emphasize minute-scale cat states of spin-5/2 ytterbium-173 atoms and the 1.4×10^3-second coherence time, but the abstract text available in those sources does not state a 10,000-atom count. (nature.com) (arxiv.org) What the paper clearly establishes is narrower and more concrete: a long-lived cat state in trapped ytterbium-173, protected well enough to support near-Heisenberg-limited magnetometry. That makes the result a sensing and measurement story first, even if the same control techniques may feed into future quantum information experiments. (nature.com) (en.ustc.edu.cn)
