Generation Of Macroscopic Entangled Cat States In A Molecular Cavity-QED System

Molecular cavity quantum electrodynamics(QED)is an emerging research direction in quantum optics,the field of molecular cavity QED mainly describes the interactions between molecules and the quantized electromagnetic fields in the cavity.Since the molecular cavity QED systems can largely suppress the decoherence of the degrees of freedom of the systems,and hence the molecules and quantized electromagnetic fields can maintain good quantum coherence within the dynamic characteristic time scale.So far,molecular cavity QED has been extensively studied theoretically and experimentally.In recent years,with the improvement of experimental technology and the rapid development of nanotechnology,strong coupling of a single molecule with plasma nanocavity at room temperature has been achieved in experiments.That is,the use of single molecule can also produce observable physical effects.Molecular cavity QED has broad development prospects,and has many practical applications in the field of quantum optics in the future.For example,the interactions of molecules with multiple degrees of freedom and quantized electromagnetic fields can be used to prepare quantum states and study the entanglement and coherence properties of quantum states.The macroscopic entangled cat state is a typical quantum state,which is of great significance not only in the demonstration of quantum physics foundations,but also in modern quantum technologies such as continuous-variable quantum information processing and quantum metrology.This article is based on the molecular cavity QED system,we propose a scheme for generation of macroscopic entangled cat states in a molecular cavity QED system.By simultaneously modulating the resonance frequencies of the molecular vibration and the cavity field,the molecular vibrational displacement can be enhanced significantly and hence macroscopic entangled cat states between the molecular vibrational mode and the cavity mode can be created.Our results will pave the way to the study of quantum physics and quantum chemistry in molecular cavity-QED systems.The full text is mainly composed of the following chapters:In the first chapter,we introduce the research background and significance of the generation of entangled coherent states in molecular cavity QED systems,then briefly introduce the basic knowledge of molecular cavity QED systems,quantum entanglement,entangled cat states,Wigner function and fidelity.In the second chapter,by introducing resonance frequency modulations to the molecular vibration and the cavity field,we obtain the macroscopic entangled cat states between the molecular vibrational mode and the cavity field mode.We also study quantum coherence effects of the generated states by calculating the joint Wigner function and the degree of entanglement.Finally,we calculate the fidelity and obtain the appropriate parameter range.In the third chapter,we study the influence of quantum dissipation on the generation of entangled cat states.For larger decay rates,the fidelity and the logarithmic negativity decay more rapidly,and the values that the fidelity and the logarithmic negativity can reach are smaller.The fourth chapter is the summary and outlook,we summarize this paper and look forward to the follow-up work.