  We study quantum critical phenomena in the microwave scattering of the
subohmic spin-boson system, which exhibits a quantum phase transition at a
critical system-reservoir coupling. By relating the reflection coefficient of a
microwave with the dynamic susceptibility of the subohmic spin-boson system, we
clarify the appearance of quantum critical phenomena in microwave scattering.
Further, we propose experimental setups to realize the subohmic spin-boson
system in a superconducting circuit composed of a charge qubit and a
dissipative transmission line.
