Identifying leakage sources in industrial factory production is crucial to improving air quality, ensuring people’s health and safety and preventing safety accidents. In this study, a method for leakage source identification in industrial factories combining with computational fluid dynamics (CFD) and correlation coefficient was proposed and validated. The study first experimentally validated the numerical methods, which were fundamental to the leakage identification method. Then impacts of leakage sources, sensor errors and number of sensors on the source identification results were evaluated. The results showed that the identification accuracy could be significantly improved by refining the step size of the coefficient ar in this method. When the number of leakage sources was unknown, the accuracy of this method in identifying the number and location of leakages was 93.5%. The computation time spent on source identification depended on the maximum number of leakage sources. Using four sensors with errors were enough to identify the number of unknown leakage sources. The number of leakage sources did not exceed three at the same time. Overall, coupled CFD and correlation coefficients method could effectively identify the number, location and intensity of leakages.

In this PhD thesis, the author first delves into the realm of quantum magnonics, focusing on the dynamics and properties of magnon modes and hybrid quantum models. The thesis introduce a comprehensive approach to studying both ferromagnetic and antiferromagnetic magnon systems using quantum mechanics tools, such as the second quantization of the spin Hamiltonian (Holstein-Primakoff transformation) and Bogoliubov transformation. This approach allows for the precise characterization of different coupling interactions, reflecting the symmetric properties of material lattice. Specifically, the author examines how these interactions enable the preparation of targeted isolated magnon (or boson) models, facilitating the control of vacuum and excited states. The thesis present a detailed analysis of the entanglement entropy of magnon modes in antiferromagnetic (AFM) materials , highlighting the role of exchange and Dzyaloshinskii-Moriya (DM) coupling terms. Moreover, the thesis propose a novel cavity magnonic setup that leverages the cavity photon degree of freedom for experimentally measuring entanglement in AFM magnon modes. Additionally, the thesis address the open system dynamics of magnon-magnon-phonon model in AFM lattice using the quantum Langevin equations. With the steady-state solution of quantum Langevin equations, one assess how external magnetic fields and temperature-dependent noise influence magnon-magnon entanglement in AFM lattice, leading to high-temperature entanglement in antiferromagnets under certain conditions.

Transitioning interest from magnons to magnetic spin systems, part of the thesis analyze the spin dynamics described by the Landau-Lifshitz equations under the quantum framework, that is explore the implications of the Landau-Lifshitz equations for quantum dynamics. The author and his colleagues propose a quantum analog of the Landau-Lifshitz-Gilbert equation as an effective equation for qubit dynamics, which has no intrinsic information loss (preserves the purity of quantum states) and is faster than classical Landau-Lifshitz-Gilbert spin dynamics. It offers a promising direction for further theoretical, computational and experimental investigation. The dynamics of quantum correlation in dimer systems are studied, providing insights into the behavior of both pure and mixed states.

This thesis not only advances our understanding of quantum entanglement and non-locality in quantum magnonics and spin dynamics but also sets the stage for future investigations into the quantum mechanical properties of novel materials and their applications in quantum information science. The methodologies and findings discussed here pave the way for developing more sophisticated quantum technologies and contribute to the broader field of quantum materials research.

I denna doktorsavhandling fördjupar sig författaren först i kvantmagnonikens värld, med fokus på dynamiken och egenskaperna hos magnonmoder och hybridkvantmodeller. Avhandlingen introducerar ett omfattande tillvägagångssätt för att studera både ferromagnetiska och antiferromagnetiska magnonsystem med hjälp av verktyg från kvantmekaniken, såsom andrakvantisering av spinn-Hamiltonianen (Holstein-Primakoff-transformationen) och Bogoliubov-transformationen. Detta tillvägagångssätt möjliggör en precis karaktärisering av olika kopplingsinteraktioner, vilket återspeglar symmetriegenskaperna hos materialets gitter. Specifikt undersöker författaren hur dessa interaktioner möjliggör förberedelse av riktade isolerade magnon- (eller boson-) modeller, vilket underlättar kontrollen av vakuum- och exciterade tillstånd. Avhandlingen presenterar en detaljerad analys av kvantsammanflätningens entropi för magnonmoder i antiferromagnetiska (AFM) material, och lyfter fram rollen hos utbytes- och Dzyaloshinskii-Moriya-kopplingstermer (DM). Dessutom föreslår avhandlingen en ny kavitetsmagnonisk uppställning som utnyttjar frihetsgraden för kavitetsfotoner för att experimentellt mäta sammanflätning i AFM-magnonmoder. Avhandlingen behandlar även dynamiken för magnon-magnon-fononmodellen i AFM-gitter med hjälp av kvant-Langevinekvationerna. Med den stationära lösningen av kvant-Langevinekvationerna bedömer man hur yttre magnetfält och temperaturberoende brus påverkar magnon-magnonsammanflätningen i AFM-gitter, vilket leder till kvantsammanflätning vid höga temperaturer i antiferromagneter under vissa förhållanden.

Från magnoner till magnetiska spinnsystem analyserar en del av avhandlingen spinndynamiken som beskrivs av Landau-Lifshitz-ekvationerna under det kvantmekaniska ramverket, vilket utforskar implikationerna av Landau-Lifshitz-ekvationerna för kvantdynamik. Författaren och hans kollegor föreslår en kvantanalog av Landau-Lifshitz-Gilbert-ekvationen som en effektiv ekvation för kvantbitdynamik, vilken inte har någon inneboende informationsförlust (bevarar renheten hos kvanttillstånd) och är snabbare än klassisk Landau-Lifshitz-Gilbert spinndynamik. Det erbjuder en lovande riktning för vidare teoretiska och experimentella undersökningar. Dynamiken för kvantkorrelation i dimersystem studeras, vilket ger insikter i beteendet hos både rena och blandade tillstånd.

Denna avhandling främjar inte bara vår förståelse av kvantsammanflätning och icke-lokalitet i kvantmagnonik och spinndynamik utan också lägger grunden för framtida undersökningar av kvantmekaniska egenskaper hos nya material och deras tillämpningar inom kvantinformationsvetenskap. De metoder och resultat som diskuteras här banar väg för utvecklingen av mer sofistikerade kvantteknologier och bidrar till det bredare fältet av kvantmaterialforskning.

The Landau-Lifshitz-Gilbert (LLG) and Landau-Lifshitz (LL) equations play an essential role for describing the dynamics of magnetization in solids. While a quantum analog of the LL dynamics has been proposed in [Phys. Rev. Lett. 110, 147201 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.147201], the corresponding quantum version of LLG remains unknown. Here, we propose such a quantum LLG equation that inherently conserves purity of the quantum state. We examine the quantum LLG dynamics of a dimer consisting of two interacting spin-12 particles. Our analysis reveals that, in the case of ferromagnetic coupling, the evolution of initially uncorrelated spins mirrors the classical LLG dynamics. However, in the antiferromagnetic scenario, we observe pronounced deviations from classical behavior, underscoring the unique dynamics of becoming a spinless state, which is nonlocally correlated. Moreover, when considering spins that are initially entangled, our study uncovers an unusual form of revival-type quantum correlation dynamics, which differs significantly from what is typically seen in open quantum systems.

We report the existence of entangled steady-states in bipartite quantum magnonic systems at elevated temperatures. We consider dissipative dynamics of two magnon modes in a bipartite antiferromagnet, subjected to interaction with a phonon mode and an external rotating magnetic field. To quantify the bipartite magnon-magnon entanglement, we use entanglement negativity and compute its dependence on temperature and magnetic field. We provide evidence that the coupling between magnon and phonon modes is necessary for the entanglement, and that, for any given phonon frequency and magnon-phonon coupling rate, there are always ranges of the magnetic field amplitudes and frequencies for which magnon-magnon entanglement persists at room temperature.

Quantum magnonics is an emerging research field, with great potential for applications in magnon based hybrid systems and quantum information processing. Quantum correlation, such as entanglement, is a central resource in many quantum information protocols that naturally comes about in any study toward quantum technologies. This applies also to quantum magnonics. Here, we investigate antiferromagnetic coupling of two ferromagnetic sublattices that can have two different magnon modes. We show how this may lead to experimentally measurable bipartite continuous-variable magnon-magnon entanglement. The entanglement can be fully characterized via a single squeezing parameter or, equivalently, entanglement parameter. The clear relation between the entanglement parameter and the Einstein, Podolsky, and Rosen (EPR) function of the ground state opens up for experimental quantification magnon-magnon continuous-variable entanglement and EPR nonlocality. We propose a practical experimental realization to measure the EPR function of the ground state, in a setting that relies on magnon-photon interaction in a microwave cavity.

Continuous variable entanglement between magnon modes in Heisenberg antiferromagnets with Dzyaloshinskii-Moriya (DM) interaction is examined. Different bosonic modes are identified, which allows us to establish a hierarchy of magnon entanglement. We argue that entanglement between magnon modes is determined by a simple lattice-specific parameter, together with the ratio of the strengths of the DM and Heisenberg exchange interactions, and that magnon entanglement can be detected by means of quantum homodyne techniques. As an illustration of the relevance of our findings for possible entanglement experiments in the solid state, a typical antiferromagnet with the perovskite crystal structure is considered, and it is shown that long wave length magnon modes have a maximal degree of entanglement.

The Landau-Lifshitz-Gilbert (LLG) and Landau-Lifshitz (LL) equations play an essential role for describing the dynamics of magnetization in solids. While a quantum analog of the LL dynamics has been proposed in [Phys. Rev. Lett. 110, 147201 (2013)], the corresponding quantum version of LLG remains unknown. Here, we propose such a quantum LLG equation that inherently conserves purity of the quantum state. We examine the quantum LLG dynamics of a dimer consisting of two interacting spin-1/2 particles. Our analysis reveals that, in the case of ferromagnetic coupling, the evolution of initially uncorrelated spins mirrors the classical LLG dynamics. However, in the antiferromagnetic scenario, we observe pronounced deviations from classical behavior, underscoring the unique dynamics of becoming a spinless state, which is non-locally correlated. Moreover, when considering spins that are initially correlated, our study uncovers an unusual form of transient quantum correlation dynamics, which differ significantly from what is typically seen in open quantum systems.