  We theoretically investigate the quantum phase transition in the collective
systems of qubits in a high-quality cavity, which is driven by a squeezed
light. We show that the squeezed light induced symmetry breaking can result in
quantum phase transition without the ultrastrong coupling requirement. Using
the standard mean field theory, we derive the condition of the quantum phase
transition. Surprisingly, we show that there exists a tricritical point where
the first- and second-order phase transitions meet. With specific atom-cavity
coupling strengths, both the first- and second-order phase transition can be
controlled by the squeezed light, leading to an optical switching from the
normal phase to the superradiant phase by just increasing the squeezed light
intensity. The signature of these phase transitions can be observed by
detecting the phase space Wigner function distribution with different profiles
controlled by the squeezed light intensity. Such superradiant phase transition
can be implemented in various quantum systems, including atoms, quantum dots
and ions in optical cavities as well as the circuit quantum electrodynamics
system.
