What limits mechanical cat-state coherence as mass grows?
In plain words
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.
Precise statement
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.
What would settle it
Systematic Wigner-function tomography of cats across masses and separations with independently measured bath parameters.
Status in the literature
Cat states of a 16-microgram oscillator were reported in 2023 (Bild et al., Science).