Electromagnetic and mechanical oscillators are crucial in such diverse fields as electrical engineering, microwave technology, optical technology, and experimental physics. For example, such oscillators are the key elements in instruments for detecting extremely weak mechanical forces and electromagnetic signals are essential to highly stable standards of time and frequency. The central problem in developing such instruments is to construct oscillators that are as perfectly simple harmonic as possible; the largest obstacle is the oscillator's dissipation and the fluctuating forces associated...