关键词: 量子信息, 量子纠缠态, 耦合态, 极化矢量, 判据

Abstract:

The problem of entangled state of two coupling spin $1/2$ particles induced by outside magnetic field was studied under Heisenberg Picture. By solving the differential equation group of systemic polarization vector varying with time using numerical method, the rule of polarization vector varying with time was obtained. Calculation results declare that the un-entangled state of two coupling parallel spin 1/2 particles with total polarized vector Z component being -2 could translate to entangled state under suitable outside magnetic field condition. The best parameters of outside magnetic field was obtained, and a new method was put forward to judge whether the system of two coupling spin 1/2 particles was in entangled state based on the change of polarization vector with time. This method wasn't built upon adiabatic approximation and could be suitable for more complicated situations such as systems with relaxation.

Key words: quantum information, quantum entangled state, coupled states, polarization vector, criterion