Optimal preparation of arbitrary quantum state of electron spins quantum-bit system based on invariant magnetic field

In the presentation of single quantum state on Bloch sphere,a strategy of optimal preparation of arbitrary quantum state of electron spin quantum systems is proposed.By using the mechanical logic gate,the manipulation of quantum system is realized by way of unitary-evolution.In the course,a switch idea for the control systems is presented. The models of quantum systems and the control systems using invariant magnetic field are then established.With the help of the Lie group and the classical control theory,a strategy of optimal preparation of arbitrary quantum state is also realized. Finally,the theoretical analysis and the simulation of the preparation indicate the advantage of the idea.