Information gain versus coupling strength in quantum measurements
Xuanmin Zhu, Yu-Xiang Zhang, Quanhui Liu, Shengjun Wu · Physical Review A · 2012
We investigate the relationship between the information gain and the interaction strength between the quantum system and the measuring device. A strategy is proposed to calculate the information gain of the measuring device as a function of the coupling strength. For qubit systems, we prove that the information gain increases monotonically with the coupling strength. It is obtained that the information gain of the projective measurement along the $x$ direction decreases with increasing measurement strength along the $z$ direction, and a complementarity of information gain in the measurements along those two directions is presented.