Exponentially enhanced sensing in a non-Hermitian topological nanomechanical network

Recent years have seen a strong interest in the possibility to enhance classical and quantum sensing in suitably engineered non-Hermitian multimode systems, displaying e.g. parity-time symmetry or topological phases. The bosonic Kitaev-Majorana chain is a proposed non-Hermitian topological model that is predicted to feature enhanced responsivity to small perturbations, linked to unidirectional amplification. We report an experimental realization of the bosonic Kitaev chain in a nano-optomechanical network, in which two-mode squeezing and beamsplitter interactions between nanomechanical modes are generated through temporally modulated radiation pressure control fields. We demonstrate that this system displays a dramatic sensitivity to boundary conditions, and a unique exponential scaling of the responsivity to a small perturbation with the number of resonators.