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    "story_id": "mp-2026-09-14-001",
    "source_story_id": "tmp-lead-qudit-backpropagation",
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    "headline": "One Ion Learned With Backpropagation",
    "slug": "one-ion-learned-with-backpropagation",
    "dek": "A trapped calcium qudit carried a quantum neural network through hybrid training and reached 95.7% classification accuracy on the reported image test.",
    "summary": "A trapped calcium qudit carried a quantum neural network through hybrid training and reached 95.7% classification accuracy on the reported image test.",
    "body_text": "Quantum neural networks are usually framed around two-level qubits, which restrict the accessible state space of each physical carrier. This experiment instead encoded a neural network in the multiple levels of one trapped calcium-40 ion and trained it with a hybrid quantum-classical implementation of backpropagation. The authors report 95.7% classification accuracy on their test image set. The result demonstrates a working qudit training loop on physical hardware, but it is a compact classification experiment rather than evidence that qudit processors already outperform mature classical systems or scale without new control and error challenges.",
    "why_it_matters": "A trapped calcium qudit carried a quantum neural network through hybrid training and reached 95.7% classification accuracy on the reported image test.",
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    "first_published_at": "2026-09-14T09:00:00.000-04:00",
    "modified_at": "2026-09-14T09:00:00.000-04:00",
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        "text": "A trapped calcium qudit carried a quantum neural network through hybrid training and reached 95.7% classification accuracy on the reported image test.",
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    "tags": [
      "qudits",
      "quantum neural networks",
      "trapped ions"
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    "image_url": "https://themachinepress.com/issues/2026-09-14/lead-qudit-backpropagation.png",
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  "sources": [
    {
      "source_id": "source-2026-09-14-001",
      "title": "arXiv preprint 2609.12500",
      "publisher": "arXiv",
      "url": "https://arxiv.org/abs/2609.12500",
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  "publisher": {
    "name": "The Machine Press",
    "url": "https://themachinepress.com",
    "description": "A daily newspaper for the age of artificial intelligence."
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  "cite_this_report": {
    "title": "One Ion Learned With Backpropagation",
    "publisher": "The Machine Press",
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