Energy And Information Transfer In Simple Photosynthesis Models And Coupled Quantum Dot System

The processes of energy and information transfer in quantum networks plays an important role in photosynthetic process as well as quantum communication and quantum computation. Quantum states are not only carriers of information but also the energy. Transfer of quantum states contacts closely with the energy and information transfer in photosynthesis and quantum dot (QD) systems. In this thesis, we shall study the processes of energy and information transfer of two typical small quantum systems:simple photosynthesis models by three spins; and coupled QD systems.This thesis is organized as follows:In chapter one we briefly review some fundamental knowledge about the en-ergy transfer in photosynthetic processes and encoding methods of qubits in DQD systems.In chapter two, we study environment-assisted excitation energy transfer ef-ficiency (EET) in LHl-RC-typc and LH2-type trimers. It is found that highly efficient EET with nearly unit efficiency may occur in the nearby regime of the quantum critic point. It indicates that the ETE sudden change caused by the QPT is suppressed at higher temperatures.In chapter three, we study quantum dynamics of entanglement and single excitation transfer (SET) in a LH1-RC-type trimer. We investigate the influ-ence of environment on entanglement and SET. We show the generation of the decherence-assisted entanglement between a donor and an acceptor and the exis-tence of the steady-state entanglement, and demonstrate the entanglement transfer from donor-donor entanglement to donor-acceptor entanglement in the dynamic evolution. We also reveal the close relation between the SET probability and do nor-acceptor entanglement.In chapter four, we propose a scheme to realize energy and quantum informa-tion transfer in a DQD system. We display quantum information transfer from a DQD system to a quantized cavity field. The DQD and the cavity field are treated as a two-state charge qubit and a continuous-variable system, respectively.In chapter five, we propose theoretical schemes to generate a controllable and switchable coupling between two DQD spin qubits as well as hybrid system made of DQD spin qubits and superconducting charge qubits by using a transmission line resonator (TLR) as a bus system. We study dynamical behaviors of quantum correlations between two DQD spin qubits. We also study the entanglement trans-fer in a hybrid circuit quantum electrodynamics system, where the memory and operation registers are, respectively, implemented using DQD and superconducting charge qubits.In chapter six, we present summary of our results and an outlook of the thesis.