Abstract In this paper, we demonstrate the exact solution of the nonstationary Schrodinger equation for the Tavis–Cummings model, in which three identical two-level atoms (qubits) are prepared in an arbitrary superposition of 8 Hilbert space vectors and which resonantly interact with a coherent resonator field mode of any intensity. The exact solution was used to calculate the parameters of atom–atom and atom-field entanglement: linear entropy, pairwise and three-particle negativity, and population inversion of three atoms. The results of computer modeling have shown that the degree of correlation between the atoms and the resonator field can significantly depend on the initial state of the atoms. Separable, biseparable, and genuine entangled W -type states demonstrate a high rate of energy exchange between atoms and the resonator field mode and the effect of sudden death of pairwise entanglement of atoms. On the contrary, all GHZ-states exhibit stable pairwise and three-particle entanglement between atoms and a slow rate of energy exchange between atoms and the resonator field mode. We also demonstrate the effect of the sudden death of three-particle entanglement for various states of atoms, the collapse and revival of the Rabi oscillations of the population inversion of three atoms, and the effect of the transition of entanglement from a subsystem of atoms to the total system. These results can be used for optimal operation of quantum networks.

Abstract Recently, machine learning has been widely applied in the field of quantum information, notably in tasks such as entanglement detection, steering characterization, and nonlocality verification. However, few studies have focused on utilizing machine learning to detect quantum information masking (QIM). In this work, we investigate supervised machine learning for detecting QIM in both pure and mixed qubit states. For pure qubit states, we randomly generate the corresponding density matrices and train an XGBoost model to detect QIM. For mixed qubit states, we improve the XGBoost method by optimizing the selection of training samples. The experimental results demonstrate that our approach achieves higher classification accuracy. Furthermore, we analyze the area under the curve of the receiver operating characteristic curve for this method, which further confirms its classification performance.

Abstract The generation, fusion, and interconversion of quantum entangled states play equally important roles in quantum information processing. In this paper, we propose a deterministic protocol to realize the interconversion between the three-electron-spin W state and the Knill–Laflamme–Milburn state by exploiting controlled quantum gates and parity-measuring devices constructed via the interaction between a photon and electron spins in silicon-vacancy system. Our analysis reveals that, considering non-ideal factors, both conversions achieve high fidelities and efficiencies. The efficient interconversion of stationary entangled states contributes to a deeper understanding of quantum entanglement and significantly contributes to quantum information processing

Abstract In this paper, a tunable and switchable erbium-doped fiber laser (EDFL) based on parallel dual Lyot filters cascaded with a Sagnac loop is proposed. The filter can be regarded as a composite filter, whose structure is composed of cascaded different filters to ensure the presented tuning range and flexibility of parameter configuration. The wavelength resolution and polarization stability of the filter are enhanced by the synergistic effect of the multistage polarization-maintaining fibers (PMFs) and polarization controllers (PCs). The experimental results show that when the pump power is 250 mW and the lengths of the PMFs used are 4 m, 4 m, and 8 m respectively, the wavelength spacing can be adjusted by tuning the three PCs in the filter, allowing the laser to be reconfigured to alter the polarization state, thereby achieving continuous excitation of 1 to 7 wavelengths in the range from 1530.52 nm to 1568.04 nm. In addition, the output wavelength is adjustable over a range of ∼37.52 nm. The side-mode suppression ratios for the output wavelengths of this laser all exceed ∼41.60 dB. The proposed EDFL has good tunability, switchability, and stability.

Abstract The effects of employing two different nonlinear crystals, MgO:PPLN (MgO-doped periodically poled lithium niobate) and LBO (lithium triborate), on output power, beam quality and frequency-doubling efficiency are studied. A continuous 532 nm green laser was generated by using a ring extra resonant cavity. Using a quasi-phase-matching MgO:PPLN crystal, 2.1 W of green laser was produced from a 4 W single-frequency fiber laser operating at 1064 nm. The beam quality factors, M 2 x and M 2 y , were measured at 1.114 and 1.189, respectively, with a power stability of 0.8%. In contrast, when using a type Ⅰ phase-matching LBO crystal, 10.6 W of 532 nm green laser was achieved and the beam quality factors, M 2 x and M 2 y , were 1.618 and 1.169, with a power stability of 1.01%. Experimental results revealed that LBO crystals exhibited randomly varying higher-order modes within the resonant cavity during frequency doubling, whereas the MgO:PPLN system maintained fundamental-mode operation, enabling easier locking, a lower output threshold, and superior power stability. However, LBO crystals demonstrated advantages in larger crystal dimensions, enhanced thermal dissipation, and higher output power.

Abstract In this study, a vortex flowmeter based on a thin-sheet optical fiber sensing structure was proposed. The flowmeter utilizes the pressure exerted by the periodic shedding vortices on the thin-sheet optical fiber sensing structure, forcing the optical fiber sensing structure to oscillate periodically and reciprocally. The vortex shedding signal was converted into a voltage signal through a phototransistor for analysis, and the vortex shedding frequency was obtained indirectly, thereby achieving the purpose of flow measurement. The flowmeter fully utilizes the benefits of optical fiber and enhances its resistance to electromagnetic interference. Through numerical simulation, experimentation and data processing, it is evident that a clear linear relationship exists between vortex shedding frequency and velocity. The experiment achieved a sensitivity of 53.964 Hz m−1 s−1. The proposed sensor has the advantages of simple structure and low cost, which is conducive to practical application.

Abstract In this paper, we study the chaotic dynamics of an optomechanical systems coupled to a non-Markovian environment. The master equation of the system is derived beyond the Markovian approximation and the maximum Lyapunov exponent is employed to quantify the generation of chaos. In contrast to the majority of existing studies on chaos generation in optomechanical systems, our work highlights that the influence exerted by the properties of the environment can be of equivalent significance to that of the system parameters, and in certain cases, the environmental parameters may be even more important. The numerical results show that the memory time and central frequency of the environment play crucial roles in the generation of chaos, and they can even determine whether chaos occurs. In addition, we also investigate the influence of system parameters and compare them with the environmental parameters. We hope the results presented in this paper open a new direction for the research on chaos generation and attract more attentions on the influence of the properties of environments.

Abstract We report on changes in absorptive, emissive and waveguiding properties of Bismuth doped yttria–aluminosilicate (Bi–Al–Y–Si) fiber under the action of high-energy electrons. In addition to the drastic rise of induced absorption in the fiber as a result of bombardment with electrons (measured by ∼800 dB m−1 in the VIS range at the maximal irradiation dose of ∼200 KGy(SiO2) or 1 × 1014 cm−2), we reveal prominent (∼20 fold at the maximal dose) growth of the fiber emissive potential in NIR (∼1.2 µm) at its pumping in VIS (at 730 nm), an effect never reported before; both phenomena are inferred to arise due to strong growth of the content of Bi-related active centers, mostly of the Bi(Al) type, at irradiation. We also report for Bi–Al–Y–Si fiber notable radiation-induced changes in the photo-bleaching behavior of the centers throughout the VIS/NIR range. Another point deserving attention is that the Stokes shift of the cutoff wavelength after irradiation is insignificant (∼25 nm at the maximal dose) in this type of fiber.

Abstract We develop a novel enhanced laser-based elastography technique that utilizes an optical coherence tomography (OCT) imaging system. This enhancement combines the capabilities of OCT with an advanced phase extraction technique, aiming to increase the precision of biomechanical measurements in soft tissues. Our approach utilizes the discrete cosine transform (DCT) for phase extraction, overcoming the limitations of vector-based methods in handling complex geometries and large displacements. Unlike fast Fourier transform-based unwrapping, DCT ensures thar the result is artifact-free. This advancement refines spatial detail in optical coherence elastography (OCE), enabling accurate mapping of tissue elasticity and structural variations. By eliminating windowing constraints, our method offers a faster, more robust solution for biomechanical diagnostics. In this study, we introduce a micro-elastography system that utilizes a 4 ohm speaker as a mechanical excitation source to apply controlled, quasi-static compressions. This system, combined with a high-speed, 100 kHz swept-source OCT laser, enables rapid data acquisition and straightforward phase-to-strain conversion. Our findings demonstrate the system’s capability of providing accurate strain mapping across a range of samples, delivering reliable elastic information despite the challenges posed by non-linear and non-uniform tissue boundaries. This study showcases the potential of DCT-based OCE to enhance clinical diagnostics and improve the characterization of diseased and tumor boundaries in soft tissues.