Enhancing mechanical entanglement in molecular optomechanics

Abstract: We propose a scheme for enhancing bipartite quantum entanglement in a double-cavity molecular optomechanical (McOM) system incorporating an intracavity optical parametric amplifier (OPA). Utilizing a set of linearized quantum Langevin equations and numerical simulations, we investigate the impact of the OPA on both optical-vibration and vibration-vibration entanglement. Our key findings reveal a counterintuitive trade-off: while the OPA significantly enhances vibration-vibration entanglement, a critical resource for quantum memories and transducers, it simultaneously suppresses optical-vibration entanglement. We demonstrate that maximal vibration-vibration entanglement is achieved when the molecular collective vibrational modes are symmetrically populated, providing a clear experimental guideline for optimizing entanglement sources. In particular, the vibration-vibration entanglement generated in our OPA-enhanced McOM system exhibits remarkable robustness to thermal noise, persisting at temperatures approaching \SI{e3}{\kelvin}, significantly exceeding conventional optomechanical systems, and highlighting the potential for room temperature quantum information processing. These results establish a promising theoretical foundation for OPA-enhanced McOM systems as a robust and scalable platform for quantum technologies, paving the way for future experimental implementations and advanced quantum information processing applications.