From Joshua Feinberg’s Lab: An idea to exploit Wigner’s cusp singularity of scattering cross sections at threshold to significantly enhance sensor sensitivity is presented, including feasibility check, in the context of avionic accelerometery.

Typical sensors detect small perturbations by measuring their effects on a physical observable, using a linear response principle (LRP). It turns out that once LRP is abandoned, new opportunities emerge. A prominent example is resonant systems operating near N-th order exceptional point degeneracies (EPD) where a small perturbation ε<<1 activates an inherently sub-linear response ∼ε^(1/N)≫ε in resonant splitting. Here, we propose an alternative sublinear optomechanical sensing scheme which is rooted in Wigner's cusp anomalies (WCA), first discussed in the framework of nuclear reactions: a frequency-dependent square-root singularity of the differential scattering cross-section around the energy threshold of a newly opened channel, which we utilize to amplify small perturbations. WCA hypersensitivity can be applied in a variety of sensing applications, besides optomechanical accelerometry discussed in this paper. Our WCA platforms are compact, do not require a judicious arrangement of active elements (unlike EPD platforms) and, if chosen, can be cavity-free. More information may be found here.