We report on the robust experimental accumulation of nonclassicallity of motion of a single trapped ion. The nonclassicality stems from deterministic incoherent modulation of thermal phonon number distribution implemented by a laser excitation of nonlinear coupling between the ion's internal - electronic levels and external - motional states. We demonstrate that the repetitive application of this nonlinear process monotonically accumulates the observable state nonclassicality. The output states converge to a phonon number distribution with high overlap with a particular Fock state and visible quantum non-Gaussian aspects including corresponding negative Wigner function. The resulting oscillator states prove deterministic transition in the hierarchy of quantum non-Gaussianity up to four phonons. This transition is very robust against experimental imperfections and produces increasing entanglement potential.
@article{arxiv.2004.12863,
title = {Unconditional accumulation of nonclassicality in a single-atom mechanical oscillator},
author = {L. Podhora and T. Pham and A. Lešundák and P. Obšil and M. Čížek and O. Číp and P. Marek and L. Slodička and R. Filip},
journal= {arXiv preprint arXiv:2004.12863},
year = {2020}
}