| Quantum communication has been an important aspect of the envisioned quantum network consisting of quantum nodes and communication channels. It involves a number of disciplines including Quantum Optics and Quantum Information. The overall framework of quantum communication involves transmit and receive nodes, and a transmission medium for the transport of photon qubit.;In the context of subject materials presented in this thesis, the phrase quantum communication refers to the communication of quantum states between spatially separated quantum processes through a waveguidance structure such as photonic crystal fiber (PCF) or optical fiber. An enhanced framework for the construction of PCF based quantum communication system is proposed. Also, a comprehensive implementation scheme is devised in order to realize the proposed framework as a computer programmable model, and a simulation platform is developed to study the system behavior through simulations of the model.;The proposed framework incorporates a sending node, a PCF and a receiving node. The sending node as well as the receiving one consist of a rubidium atom ( 87 Rb ) trapped at the center of a cavity. In the sending node, binary logic states '0' and '1' are represented by two subspaces S0 and S 1 of the Hilbert space corresponding to the hyperfine states of the 87 Rb atom - S0 is spanned by the basis states (52S1/2, F = 1, mF = 0), (52 P1/2, F = 1, mF = 0) and (52P1/2, F = 2, mF = 1), and S1 by the basis states (52S1/2, F = 1, mF = 1), (52 P1/2, F = 1, mF = 1) and (52P3/2, F = 2, mF = 0). In the receiving node, two basis states (52S1/2, F = 1, mF = 1) and (52S 1/2, F = 1, mF = 0) within a single subspace represent logic states '0' and '1', respectively. These basis states are hyperfine states of the 87 Rb atom with magnetic sublevels split upon application of a static magnetic field (i.e. due to Zeeman effect).;The quantum state transfer from the sending node to the receiving node is achieved by generating (in the sending node) a photon with energy and polarization states corresponding to the logic state of the node. The photon propagates through the PCF. Once the photon reaches the receiving node, a quantum process switches the logic state of the receiving node to the original state of the sending node carried by the received photon.;As part of the system model, Hilbert spaces and density matrices are constructed, Hamiltonians are formulated, and equations for evolutions of the density matrices are developed. The model is simulated to examine quantum state transfer from the sending to the receiving node. In this context, closed- and open-system simulations are performed. The simulation results show efficacy of the approach, as determined by the observation of transferring the logic state of the sending node to the receiving one.;The main contribution of this thesis is the proposal of an enhanced framework which solves the problem of undesirable toggling of the qubit state at the sending node while transmitting the qubit state, as reported in the earlier works. The problem is solved by encoding the logical basis of the qubit into two subspaces of the multiple hyperfine energy levels of Rubidium ( 87Rb ) atom. |
