Quantized mode of a leaky cavity - art. no. 063805

We use Thomson's classical concept of mode of a leaky cavity to develop a q uantum theory of cavity damping. This theory generalizes the conventional s ystem-reservoir theory of high-P cavity damping to arbitrary Q. The small s ystem now consists of damped oscillators corresponding to the natural modes of the leaky cavity rather than undamped oscillators associated with the n ormal modes of a fictitious perfect cavity. The formalism unifies semiclass ical Fox-Li modes and the normal modes traditionally used for quantization. It also lays the foundations for a full quantum description of excess nois e. The connection with Siegman's semiclassical work is straightforward. In a wider context, this theory constitutes a radical departure from present m odels of dissipation in quantum mechanics: unlike conventional models, syst em and reservoir operators no longer commute with each other. This noncommu tability is an unavoidable consequence of having to use natural cavity mode s rather than normal modes of a fictitious perfect cavity.