Zenith of the quantum doctrine: Dissection of the uses and misuses of quantum theory in the quest for macroscopic mechanical quanta

The reflections composing this thesis examine the usage and necessity of quantum theory, with an emphasis on systems featuring mechanical resonators. The first chapter introduces the quantum formalism, reviews the historical motivation for the quantization of harmonic oscillators, and presents a derivation of the interaction between the electromagnetic field and mechanical motion in several distinct systems. The second chapter examines the nature of physical effects such as state transfer, squeezing, entanglement, and sideband asymmetry, and how they naturally emerge in non-quantum contexts. A dynamical statistical theory is introduced to aid the quantum/classical comparison, and standard measurement models are reviewed due to their strict connection to non-classicality criteria. The third chapter deals uniquely with quantum effects occurring in systems with mechanical elements, such as phonon anti bunching, parametric down conversion in electromechanical systems, creation and interference of macroscopic super positions in spin-cantilever systems, and collapse and revivals of mechanical motion and mechanical state dependent transmission in membrane-in-the-middle geometries. The fourth and last chapter discusses pervading issues with defining the classical limit, the quantum/classical comparison and definitions of non-classicality.