By studying the two operators used in quantum searching, we find the similarity between the quantum searching and the course of two body elastic collision. This similarity can help one to understand quantum coherence.
As two forms of the quantum entanglement control (QEC), the quantum entanglement swapping and preservation are demonstrated in a three-qubit nuclear magnetic resonance (NMR) quantum computer. The pseudopure state is prepared to represent the entangled states through macroscopic signals. Through controlling the interactions between the system and its environment, we can preserve an initial entangled state for a longer time. Experimental results show an agreement between theory and experiment.
