{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"005e0b0c888feb9bc5dda2691840ce021aded3c49d0918f977f7c55f61daaa3f","created":"2026-10-03T07:18:10Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["09f470c339a8d0c8d8622f5fdaf86b26a93181d42ef096b50560fb0e0922a674","5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"fd4c372745700ac24db6cf3a0761688bf010db75cfa7496b6c863d45e7796992","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"qi.macro-superpositions.levitated-nanoparticle-superposition","kind":"well-posed","literature_status":"open","n":"1","parents":[{"note":"","parent_revision":"09f470c339a8d0c8d8622f5fdaf86b26a93181d42ef096b50560fb0e0922a674","relation":"special_case"}],"plain":"A glass bead about a hundred nanometers across can be held by laser light and cooled to its lowest quantum state of motion. The next step is a superposition of two places farther apart than the bead's own size, confirmed by interference.","posed_since":"","precise":"For an optically or magnetically levitated dielectric particle of mass about $1e-15 \\text{ to } 1e-14\\,\\mathrm{g}$ (radius $r \\sim 5e-6 \\text{ to } 1e-5\\,\\mathrm{cm}$) prepared near its motional ground state, create a coherent spatial superposition or wave packet with coherence length exceeding $r$, and verify coherence by interference fringes or Wigner-function negativity, since position variance alone does not distinguish coherent from incoherent spreading.","problem_ref":null,"references":"","settled_by":"Release-and-recapture or inverted-potential interferometry showing center-of-mass interference fringes from a separation larger than r.","status_note":"In 2024 a ground-state-cooled nanoparticle's coherence length was increased more than threefold (arXiv:2408.01264) and a pre-cooled nanoparticle's motional state was expanded beyond its size (arXiv:2408.09596); no interference fringes at separations above the particle size were found in the literature checked.","title":"Spatial superposition of a levitated nanoparticle larger than its 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