Role of initial quantum correlation in transient linear response

The linear transient response of a two-level system coupled with an environmental system is studied under correlated and factorized initial conditions. We find that the transient response in these cases differs significantly from each other, especially for strong system-environment interaction at intermediate temperatures. This means that it is necessary to pay attention to the initial conditions chosen when analyzing experiments on transient linear response, because the conventional factorized initial condition results in an incorrect response, in which the quantum correlation between the relevant system and the environmental system is disregarded.