  We investigate a superconducting circuit consisting of multiple
capacitively-coupled charge qubits. The collective Rabi oscillation of qubits
is numerically studied in detail by imitating environmental fluctuations
according to the experimental measurement. For the quantum circuit composed of
identical qubits, the energy relaxation of the system strongly depends on the
interqubit coupling strength. As the qubit-qubit interaction is increased, the
system's relaxation rate is enhanced firstly and then significantly reduced. In
contrast, the inevitable inhomogeneity caused by the nonideal fabrication
always accelerates the collective energy relaxation of the system and weakens
the interqubit correlation. However, such an inhomogeneous quantum circuit is
an interesting test bed for studying the effect of the system inhomogeneity in
quantum many-body simulation.
