We studied the nonequilibrium dynamics of the indirect mixing of two (pseudo-)scalar fields induced by their couplings to common decay channels in a medium. The effective non-Markovian quantum master equation (QME) for the two fields' reduced density matrix is derived to leading order in the couplings of the two fields with the medium, but to all orders of the couplings among degrees of freedom in the medium. The self-energy and noise-kernel in the QME satisfy a fluctuation-dissipation relation. The solutions show that an initial expectation value (condensate) of one field induces a condensate of the other field through the indirect mixing and that the populations and coherence of the two fields thermalize and approach to non-vanishing values asymptotically. The nearly-degenerate field masses and coupling strengths resonantly enhance the quantum beats and asymptotic coherence, and induce a prominent dynamics of the vacuum after the switch-on of the couplings. We argue that a time-dependent definitions of particles due to the changing vacuum must be introduced so as to obtain results consistent with the calculations of equilibrium states in the asymptotic limit. A coupling strength hierarchy breaks down the resonant enhancement in the nearly-degenerate case but leads to different power countings of the coupling strengths in the magnitudes of the observables and time-scales in the evolution, suggesting the possibility of detecting extremely long-lived particles using prepared short-lived particles within a practical experimental period.
Giant third-order polarization rotation via wave-mixing-induced symmetry breaking in a Rydberg-EIT medium
School of Physics, East China Normal University（华东师范大学物理系）；School of Physical Science and Technology, Soochow University（苏州大学物理科学与技术学院）；Division of Precision Measurement Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences（中国科学院精密测量科学与技术创新研究院精密测量物理研究室）
Sideband fingerprints of antibunched light in cascaded quantum wave mixing
Dukhov Research Institute of Automatics (VNIIA)（杜霍夫自动装置研究所）；Moscow Institute of Physics and Technology（莫斯科物理技术学院）；Institute for Theoretical and Applied Electrodynamics, Russian Academy of Sciences（俄罗斯科学院理论与应用电动力学研究所）；Kotelnikov Institute of Radioengineering and Electronics, Russian Academy of Sciences（俄罗斯科学院科捷利尼科夫无线电工程与电子研究所）；Skolkovo Institute of Science and Technology（斯科尔科沃科学技术学院）
