@article{1773, abstract = {The quantum properties of electromagnetic, mechanical or other harmonic oscillators can be revealed by investigating their strong coherent coupling to a single quantum two level system in an approach known as cavity quantum electrodynamics (QED). At temperatures much lower than the characteristic energy level spacing the observation of vacuum Rabi oscillations or mode splittings with one or a few quanta asserts the quantum nature of the oscillator. Here, we study how the classical response of a cavity QED system emerges from the quantum one when its thermal occupation-or effective temperature-is raised gradually over 5 orders of magnitude. In this way we explore in detail the continuous quantum-to-classical crossover and demonstrate how to extract effective cavity field temperatures from both spectroscopic and time-resolved vacuum Rabi measurements.}, author = {Johannes Fink and Steffen, L. Kraig and Studer, Peter and Bishop, Lev S and Baur, Matthias P and Bianchetti, R and Bozyigit, Deniz and Lang, C and Filipp, Stefan and Leek, Peter J and Wallraff, Andreas}, journal = {Physical Review Letters}, number = {16}, publisher = {American Physical Society}, title = {{Quantum-to-classical transition in cavity quantum electrodynamics}}, doi = {10.1103/PhysRevLett.105.163601}, volume = {105}, year = {2010}, }