{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"4f114e37500d26eadd97a23a43911e6e3fcaec096bd1f532695783ab8f1f4db4","created":"2026-10-03T07:17:53Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"0a45d2386a6ec522c683f8c86e0eb2dcf5e0a88881f7e863667064837de139d3","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"amo.macroscopic-optomechanics.mechanical-cat-decoherence","kind":"phenomenon","literature_status":"open","n":"1","parents":[],"plain":"A 16-microgram vibrating crystal has been put into a cat state, a superposition of two distinct motions. The question is whether its decay is fully explained by known noise, or whether something extra appears at larger mass.","posed_since":"","precise":"Mechanical resonator of effective mass $m_{\\mathrm{eff}}$ in a cat state |alpha> + |-alpha>. Measure the cat decoherence rate $\\Gamma_{\\mathrm{cat}}$ versus $\\mid\\alpha\\mid^2$ and $m_{\\mathrm{eff}}$, and compare with the bath model $\\Gamma_{\\mathrm{cat}} = 2 \\mid\\alpha\\mid^2 \\Gamma_{\\mathrm{m}} (2 n_{\\mathrm{th}} + 1)$, with $\\Gamma_{\\mathrm{m}}$ the mechanical energy damping rate and $n_{\\mathrm{th}}$ the thermal phonon number, plus two-level-system defect noise. Answer: whether all decoherence is accounted for, and any excess as a function of mass.","problem_ref":null,"references":"","settled_by":"Systematic Wigner-function tomography of cats across masses and separations with independently measured bath parameters.","status_note":"Cat states of a 16-microgram oscillator were reported in 2023 (Bild et al., Science).","title":"What limits mechanical cat-state coherence as mass 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