  A Maxwell demon can reduce the entropy of a quantum system by performing
measurements on its environment. The nonsignaling theorem prevents the demon
from affecting the average state of the system. We study the preparations of
quantum correlations from a system qubit and an auxiliary qubit, assisted by a
demon who obtains information of the system qubit from measurements on its
environment. The demon can affect the postmeasured states of system by choosing
different measurements, which establishes the relationships between quantum
steering and other correlations in the thermodynamic framework. We present the
optimal protocols for creating mutual information, entanglement, and
Bell-nonlocality. These maximal correlations are found to relate exactly to the
steerable boundary of the system-environment state with maximally mixed
marginals. We also present upper bounds of the prepared correlations by
utilizing classical environment-system correlation, which can be regarded as
steering-type inequalities bounding the correlations created with the aid of
classical demons.
