Dartmouth Events

Abstract: Experiments tell us that our world is actually made of very small objects that obey quantum mechanics, and these small objects are not well described as particles with defined trajectories. This leads to a fundamental question about the nature of our world: how does the classical world manifest and to what degree can we make objects that blur the line between quantum and classical? The field of circuit Quantum Electrodynamics(cQED) deals with the quantum mechanics of small circuit devices and offers us a way to explore ideas such as the quantum to classical correspondence. We provide a theoretical model for a design involving a dc voltage biased Josephson Junction (JJ) that strongly drives a high quality factor microwave cavity via the ac Josephson effect. We explore the rich classical dynamics of the resultant non-linear differential equation that categorizes the system. We contrast this with the quantum dynamics as derived by a model using the so called Rotating Wave Approximation Hamiltonian, and independently a Floquet analysis approach where no approximation is made on the Hamiltonian. We find that for certain parameters there is evidence of quantum activation, a process of over barrier transitions that stems from purely quantum mechanical considerations, and define an effective temperature that is non-zero even when coupled to a zero temperature bath.