Stable Quantum Links Between Light and Microwaves Persist Even during Change
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Researchers have established a general theoretical framework to characterise stable quantum resources linking microwave and optical modes within complex hybrid systems utilising intermediary modes. Fan Li and Shi-fan Qi, from the HK Institute of Quantum Science & Technology and Department of Physics, The University of Hong Kong, working with Z. D. Wang and Yan-Kui Bai from College of Physics and Hebei Key Laboratory of Photophysics Research and Application, Hebei Normal University, demonstrate how strong interactions within a microwave-intermediary-optical hybrid system formulate an effective Hamiltonian for microwave-optical squeezing. Their analytical solutions reveal that stable microwave-optical resources can persist even during unsteady system evolution, potentially exceeding the quality of resources found in steady-state scenarios.
This research is significant because it provides a means to efficiently control these stable resources, as well as one-way and two-way steerings, by adjusting the effective coupling strength, and validates the theory through application to electro-optomechanical and cavity optomagnomechanical hybrid systems.
Scientists have engineered a pathway for remarkably stable quantum information transfer between microwave and optical signals, a crucial step towards scalable quantum technologies. This work details a theoretical framework demonstrating how to maintain the integrity of quantum resources, specifically entanglement and quantum steering, during transmission between these disparate signal types. The research introduces a system leveraging a chain of ‘N’ intermediate modes, effectively acting as stepping stones to facilitate this stable transfer, and suggests this approach offers improved performance beyond traditional steady-state methods. The ability to reliably interface microwave and optical quantum systems is paramount for building a functional quantum internet. Microwave photons excel at controlling quantum systems, while optical photons are ideal for long-distance communication. Directly converting information between these frequencies is challenging due to their significant difference, a problem this study circumvents by formulating an effective Hamiltonian, a mathematical description of the system’s energy, for microwave-optical squeezing, achieved through strong interactions within a hybrid system. Rigorous analytical solutions derived from this Hamiltonian reveal that stable quantum resources are not only possible but can be enhanced in unsteady, dynamic evolution. Researchers demonstrate that stable microwave-optical resources can persist even as the system evolves beyond a static equilibrium, exhibiting superior qualities compared to those limited by steady-state conditions. The stability and quality of these resources are efficiently controlled by adjusting the effective coupling strength between the system’s components, achieved through a carefully designed architecture incorporating ‘N’ intermediary modes, which act as a conduit for quantum information. The validity of this theoretical approach has been confirmed through application to established models, including electro-optomechanical and cavity optomagnomechanical hybrid systems. This theoretical framework provides a general approach to generating microwave-optical entanglement and quantum steering by constructing an effective two-mode squeezing coupling, assisted by these chain-coupled intermediate modes. By solving the system dynamics analytically using quantum Langevin equations, precise formulas for entanglement and steering have been obtained, enabling fine-tuned control via modulation of the coupling strength. A linearized multipartite Hamiltonian serves as the foundation for this work, enabling the detailed characterisation of stable quantum resources between microwave and optical modes. This approach facilitates analysis of hybrid systems incorporating intermediary modes, crucial for mediating interactions between disparate quantum platforms. The study formulates an effective Hamiltonian describing microwave-optical squeezing, achieved through strong interactions within the microwave-intermediary-optical system, yielding rigorous solutions for the dynamics of both microwave-optical entanglement and quantum steering, allowing precise prediction of resource behaviour. To model these complex interactions, the research focuses on two specific hybrid systems: an electro-optomechanical system and a cavity optomagnomechanical system. In the electro-optomechanical setup, a mechanical mode acts as the interface coupling microwave and optical modes, with a linearized Hamiltonian derived to describe the system’s behaviour. Perturbation theory is then applied to construct an effective Hamiltonian, simplifying the analysis while retaining key physical insights, allowing for the analytical determination of dynamical microwave-optical quantum resources, including entanglement and steering, and their corresponding stationary values. Validation of the analytical approach is achieved through comparison with numerical simulations of the full system dynamics, demonstrating strong agreement and confirming the accuracy of the theoretical framework. The characteristic time, τ, is introduced to define the point at which the evolution of entanglement and steering converges with the analytical stationary values, providing a metric for assessing the stability of quantum resources. A similar methodology is then applied to the cavity optomagnomechanical system, utilising a YIG crystal within microwave and optical cavities to facilitate interactions and derive a corresponding linearized Hamiltonian. Detailed analysis of the electro-optomechanical system shows good agreement between analytical predictions and full system dynamics, with quantum resources stabilising before the characteristic time, τ. The stationary values of microwave-optical quantum resources were plotted as the coupling strength, ga, increased, aligning with numerical results obtained at times τ and 2τ. Furthermore, the study establishes a regional diagram for stable microwave-optical entanglement, revealing the boundaries between steady-state and unsteady-state evolutions in the cavity optomagnomechanical system. In the cavity optomagnomechanical system, the microwave-optical entanglement Eac(τ) and quantum steering Sa→c(τ) were plotted alongside the relative decay rates of microwave and optical modes at the characteristic time τ, demonstrating that the analytical method accurately reproduces the numerical results from full system dynamics, confirming the generation of stable quantum resources. Dynamical resources Eac(2τ) and Sa→c(2τ) were found to be nearly identical to those at time τ, further validating the stability of the generated quantum resources. The efficient quantum control over microwave-optical entanglement and steering is demonstrated, with the value of E²ac(τ) closely approximating that of E²a|mbc(τ) and the values of other two-mode resources being negligibly small.
Scientists have demonstrated a pathway to more robust quantum communication between different types of quantum systems, specifically bridging the gap between microwave and optical signals. For years, a major obstacle in building practical quantum networks has been the difficulty of efficiently and reliably transferring quantum information between these disparate forms, each suited to different tasks and distances. This work offers a theoretical framework showing how to establish and maintain stable quantum links using intermediary modes, essentially, stepping stones, to facilitate the conversion. The theoretical model utilizes a chain of ‘N’ intermediary modes, suggesting a degree of scalability that is crucial for building larger, more complex quantum devices. What makes this work notable is not just the preservation of quantum resources, but the potential to enhance them during transmission. Conventional wisdom often assumes some loss of fidelity as quantum information travels, but this research indicates that, under certain conditions, the signal quality can actually improve. This is a counterintuitive and potentially significant finding, suggesting that carefully engineered intermediary stages can act as amplifiers of quantum coherence. However, the study remains firmly within the realm of theory, with the framework applied to specific physical systems, electro-optomechanical and cavity optomagnomechanical setups, which are still complex and challenging to implement perfectly in a laboratory. The precise control required over these intermediary modes, and the mitigation of environmental noise that inevitably degrades quantum states, represent substantial hurdles. Looking ahead, this research will likely inspire more detailed investigations into the optimal design of these intermediary systems, potentially incorporating superconducting circuits, trapped ions, or even quantum dots, with the ultimate goal of realising a quantum internet. 👉 More information 🗞 General Theory of Stable Microwave-Optical Quantum Resources in Hybrid-System Dynamics 🧠 ArXiv: https://arxiv.org/abs/2602.10581 Tags: