Enhanced photon squeezing in two-photon Dicke model

We explore the phenomena of quadrature squeezing of photons in the two-photon Dicke model under the mean-field approximation in the thermodynamic limit. An effective squeezing of the photonic quadratures beyond the standard quantum limit is observed in the superradiant phase. The magnitude of squeezing is enhanced, and it persists longer as one moves away from the phase boundary and approaches the boundary between the superradiant phase and the unbounded region. This unbounded region is encountered where the coupling strength is of the same order of magnitude as one of the fundamental frequencies of the system. We find that the squeezing is prolonged near the said boundary for varying transition energy of the qubits. Furthermore, we explore the critical behavior of photon squeezing near the unbounded region. (c) 2022 Elsevier B.V. All rights reserved.