Title: Work fluctuations of Brownian harmonic oscillators driven by "active-like'' viscoelastic baths

Abstract: We experimentally and theoretically investigate the dynamics and work fluctuations of an optically trapped micro-particle in a viscoelastic medium driven by an external Ornstein-Uhlenbeck (OU) noise. Compared to a viscous medium of the same zero-shear viscosity, we find a significant increase ($\sim 50 \%$) in the mean transferred power from the external forcing of a fixed noise strength to the particle due to the slow relaxation process of the viscoelastic medium considered in this study. The memory of the viscoelastic medium also leads to a small increase in the effective temperature of the particle and a high fluctuation in the work done by the external forcing. Consequently, as opposed to a viscous medium, negative work-fluctuations reduce extremely fast. This leads to the violation of the work fluctuation theorem (WFT) for a very small external noise, which may even be only $\sim 25\%$ of the thermal noise strength in a non-Markovian viscoelastic bath. We further show that all the experimental findings can be described excellently from the Langevin dynamics of the process. Finally, we formulate the appropriate WFT for such a system from the calculated work probability density function.