Composed Of Qubit Anisotropic Heisenberg Spin Chain And Its A Universal Quantum Logic Gate,

Changes occurring to a quantum state can be described using the language of quantum computation. Analogous to the way a classical computer is built from an electrical circuit containing wires and logic gates, a quantum computer is built from a quantum circuit containing wires and elementary quantum gates to carry around and manipulate the quantum information.Qubit gates include single qubit gates and multiple qubit gates. The important ones of the qubit gates are single qubit gates and the controlled-NOT gate because of the following remarkable universality result: Any multiple qubit logic gate may be composed from controlled-NOT gate and single qubit gates. Now there are some schemes for implementation of qubit gate, for example, the simple harmonic oscillator, cavity quantum electrodynamics devices,ion traps,nuclear magnetic resonance with molecules,quantum dots and some other physical systems.We investigate an annular spin cluster made of three particles with an isotropic Heisenberg-chain controlled by a time-dependent magnetic field. The system has an SU(2) algebraic structure. Using algebraic dynamical method, we have obtained the exact analytical solution to the time dependent Schro|¨dinger equation. Based on the analytical solution, it is shown that the system can be used as a universal single qubit logic gate controlled by the strength and frequency of the magnetic field, and consequently the six special single qubit logic gates can be realized.