Hamiltonian Formulation For Single/few Photon Detection

Fully quantum mechanical models for device models of single photon detectors have recently been developed. Detection of single/few photons in both inanimate devices and biological eyes have the universal structure of absorption, amplification and measurement stages. Previous models succeeded in developing definite models for all stages but the amplification stage. We write out explicit Hamiltonians that can describe such irreversible changes and also measurement induced decoherence. The time evolutions created by these Hamiltonians are solved in the discrete part of the Hilbert space and the desired dynamics are verified. Previous proposals of minimum noise amplification schemes are completed with specific Hamiltonians presented in this dissertation. A new kind of problem where a molecule absorbs two photons sequentially is investigated. The proposed Hamiltonian method is matched with a classic method in the field called ``generalized density matrix operator method'' to calculate the probabilities for such sequential absorption of photons