Modern nonequilibrium statistical mechanics provides derivations of the second law of thermodynamics based on the microscopic quantum dynamics of thermodynamic systems. By combining the derivations with quantum information theory, generalizations of the second law of thermodynamics have been derived for quantum information processing such as quantum measurement, quantum feedback control, and information erasure. Moreover, generalized nonequilibrium equalities such as the fluctuation theorem and the Jarzynski equality have been derived in the presence of feedback control. These results are applicable to small thermodynamic systems that can be precisely controlled by modern experimental technologies. These results are also closely related to the fundamental problem of Maxwell’s demon, which can be regarded as a feedback controller acting on thermodynamic systems.