Squeezing in the quantum Rabi model with parametric nonlinearity
Department of Theoretical Sciences, S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, 700106, Kolkata, India
2 Department of Physics, Ramakrishna Mission Residential College, 700103, Narendrapur, Kolkata, India
Accepted: 25 April 2021
Published online: 24 May 2021
The squeezing effect arising in the interacting qubit-oscillator system is studied with the presence of a parametric oscillator in the Rabi model. To solve the system, we employ the generalized rotating wave approximation which works well in the wide range of coupling strength as well as detuning. The analytically derived approximate energy spectrum portrays good agreement with the numerically determined spectrum of the Hamiltonian. For the initial state of the bipartite system, the dynamical evolution of the reduced density matrix corresponding to the oscillator is obtained by partial tracing over the qubit degree of freedom. The oscillator’s reduced density matrix yields the nonnegative phase space quasi-probability distribution known as Husimi Q-function which is utilized to compute the quadrature variance. It is noticed that the squeezing produced in the oscillator sector gets reduced with increasing coupling strength. We demonstrate the role of the parametric term to obtain adequate squeezing in the strong coupling regime. We also study the revival–collapse phenomenon and the generation of squeezed coherent state.
© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2021