Novel scheme for anti-dynamical Casimir effect using nonperiodic ultrastrong modulation

Dynamical Casimir effect (DCE) denotes a plethora of phenomena characterized by generation of quanta (usually photons) from vacuum due to modulation of parameters of some neutral system. Its counterpart, or Anti-DCE, can be defined as a process in which photons, as well as overall system excitations, are annihilated from the thermal state of the field due to variation of system parameters. In this paper is proposed a new fast scheme for Anti-DCE based on coupling a single-mode cavity to a qubit with time-dependent coupling strength g=εsin⁡ηt, where the modulation frequency η is a linear or quadratic function of time and ε lies in the ultrastrong coupling regime. Numeric solutions of time-dependent Rabi Hamiltonian illustrate some convenient forms of η that reduce the average number of system excitations for initial thermal and Poissonian mixed states, and modification of the photon statistics is discussed. •Novel proposal to reduce the average numbers of photons and overall system excitations.•Quantum Rabi model with time-dependent atom-field coupling in the ultrastrong coupling regime.•Modulation frequency is a linear or quadratic function of time.•Examples illustrate modification of photon statistics for thermal and Poissonian mixed states.