Zero-point fluctuations of quantized electromagnetic fields in time-varying linear media

If the precise nonclassical behavior of radiation fields is to be investigated, it is crucial to quantize the electromagnetic fields. The traditional quantization procedure is extended to that of light described by time-dependent Hamiltonians by means of the Lewis-Riesenfeld invariant operator method. The quantization problem of light fields is presented in time-varying linear media by using the invariant operator theory of Lewis-Riesenfeld. The zero-point fluctuation of the electromagnetic fields in time-varying linear media is investigated. Since there are infinite modes inside a cavity, the fluctuation of the zero-point field is also infinite. However, in view of electrical engineering, the width of the band is finite enough that the infinite zero-point fluctuation can not be detected. As a means of detection for the zero-point fluctuation, an electron that interacts with the fluctuation of the field is considered. When there is conductivity in the media, the measured total fields decrease with time due to dissipation.