Cavity electromechanics across a quantum phase transition

Quantum mechanics is our most successful theory of reality, yet, one of its enduring mysteries is that it does not seem to apply to the everyday world. In recent years, physicists have learned to explore this apparent paradox by coupling the motion of massive objects to small quantum- mechanical systems. So far, all of these systems have obeyed the predictions of quantum mechanics to a high degree of accuracy. Perhaps, the thinking goes, we will someday find a system which just doesnt want to show quantum behavior. In the meantime, we have also discovered that coupling massive objects to quantum systems is useful for technology. It might be the best way to process the delicate signals needed for quantum computers and quantum networks. Scaling up from a single quantum system, this project explores the simultaneous coupling of a single massive object to thousands of quantum-mechanical objects. The trick of our approach is that the collective behavior of quantum systems can in some cases be surprisingly simple. In the specific case we explore, we expect collective behavior that will greatly enhance the coupling to mechanical motion, which will be useful for quantum-information applications. More speculatively, it is also interesting to wonder if coupling mechanical motion to a complex quantum system, rather than a simple one, could help shed light onto the emergence of classical physics from quantum mechanics

Most superconductors' performance is improved by decreasing temperature. We found evidence of the opposite case. Namely, we built a system that is believe to insulate at zero temperature, but nevertheless displays superconducting behavior when measured at nonzero temperatures. This demonstrates an unusual case where superconductivity is apparently improved by elevated temperatures.