Science China Physics, Mechanics & Astronomy最新文献

We investigate the sensitivity and performance of space-based optical lattice clocks (OLCs) in detecting gravitational waves, in particular the stochastic gravitational wave background (SGWB) at low frequencies (10⁻⁴, 1) Hz, which are inaccessible to ground-based detectors. We first analyze the response characteristics of a single OLC detector for SGWB detection and compare its sensitivity with that of laser interferometer space antenna (LISA). Due to longer arm lengths, space-based OLC detectors can exhibit unique frequency responses and enhance the capability to detect SGWB in the low-frequency range, but the sensitivity of a single OLC detector remains insufficient overall compared with LISA. Then, as a preliminary plan, we adopt a method of cross-correlation on two OLC detectors to improve the signal-to-noise ratio (SNR). This method leverages the uncorrelated origins but statistically similar properties of noise in two detectors while the SGWB signal is correlated between them, thus achieving effective noise suppression and sensitivity enhancement. Future advancements in OLC stability are expected to further enhance their detection performance. This work highlights the potential of OLC detectors as a promising platform for SGWB detection, offering complementary capabilities to LISA, and opening an observational window into more astrophysical sources and the early universe.

Erbium-doped lithium niobate (LN) on insulator active devices, such as lasers and amplifiers, have received increasing attention. The nonlinear optical oscillation in them at high power destabilizes the output of signals and cannot be ignored. In this study, we reported the experimental observation and theoretical analysis of the nonlinear optical oscillation in erbium-doped lithium niobate-on-insulator (LNOI) microring resonators while scanning the pump wavelength. Under the same pump power, the number of oscillation cycles decreases when the wavelength scanning rate increases from 10.6 to 33.9 nm/µs. A theoretical model based on the competition between the thermo-optic nonlinearity and the photorefractive effect was introduced to interpret the oscillation in transmission. A series of parameters were obtained from the comparison between the theoretical and experimental results; some of them, the relaxation rates of the thermal and the electric field, are significantly different from those of undoped LNOI microcavities. This work provides a valuable reference for future applications of active LNOI devices.

The Earth’s climate operates as a complex, dynamically interconnected system, driven by both anthropogenic and natural forcings and modulated by nonlinear interactions and feedback loops. This study employs a theoretical framework and the Eigen Microstate (EM) approach of statistical physics to examine global surface temperature variations since 1948, as revealed by a global reanalysis. We identified EMs significantly correlated with key climate phenomena such as the global monsoon system, tropical climates, and El Niño. Our analysis reveals that these EMs have increasingly influenced global surface temperature variations over recent decades, highlighting the critical roles of hemispheric differences, land-sea contrasts, and tropical climate fluctuations in a warming world. Additionally, we used model simulations from more than 10 Coupled Model Intercomparison Project Phase 6 (CMIP6) under three future climate scenarios to perform a comparative analysis of the changes in each EM contribution. The results indicate that under future warming scenarios, tropical climate fluctuations will become increasingly dominant, while traditional hemispheric and monsoonal patterns may decline. This shift underscores the importance of understanding tropical dynamics and their impact on global climate from a physics-based perspective. Our study provides a new perspective on understanding and addressing global climate change, enhancing the theoretical foundation of this critical field, and yielding findings with significant practical implications for improving climate models and developing effective mitigation and adaptation strategies.

Topological metals possess various types of symmetry-protected degenerate band crossings. When a topological metal becomes superconducting, the low-energy electronic excitations stemming from the band crossings located close to the Fermi level may contribute to highly unusual pairing symmetry and superconducting states. In this work, we study the electronic band structure of the time-reversal symmetry breaking superconductor LaNiGa₂ by means of quantum oscillation measurements. A comprehensive investigation combining angle-resolved high-field de Haas-van Alphen (dHvA) spectroscopy and first-principles calculations reveals the fermiology of LaNiGa₂ and verifies its nonsymmorphic Cmcm lattice symmetry, which promises nodal band crossings pinned at the Fermi level with fourfold degeneracies. Moreover, such nodal structures, proposed to play a crucial role giving rise to the interorbital triplet pairing, are indeed captured by our dHvA analysis. Our results identify LaNiGa₂ as a prototypical topological crystalline superconductor and highlight the putative contribution of low-energy nodal quasiparticles to unconventional superconducting pairing.

The Taurus region is one of the most extensively studied star-forming regions (SFRs). Surveys indicate that the young stars in this region are comprised of young stellar objects (YSOs) that cluster in groups associated with the molecular cloud (Grouped Young Stellar Objects, GYSOs), and some older ones that are sparsely distributed throughout the region (Distributed Young Stellar Objects, DYSOs). To bridge the age gap between the GYSOs (⩽5 Myr) and the DYSOs (10–20 Myr), we conducted a survey to search for new YSOs in this direction. Based on infrared color excesses and Li I absorption lines, we identified 145 new YSOs. Combining these with the previously identified GYSOs and DYSOs, we constructed a sample of 519 YSOs that encompass the entire region. Subsequently, we calculated the ages of the samples based on their proximity to the local bubble. The age versus distance to the local bubble (D_LB) relationship for the DYSOs shows a clear trend: the farther they are from the local bubble, the younger they are, which is consistent with the supernovae-driven formation scenario of the local bubble. The GYSOs also exhibit a mild age versus D_LB trend. However, they are significantly younger and are mostly confined to distances of 120 to 220 pc. Considering their distribution in the age versus D_LB space is well separated from the older DYSOs, they may also be products of the local bubble but formed in more recent and localized events.

Hybrid glasses are a novel class of glass formers that possess unique coordination bonds. Size effects on vitrification have been observed in other glassy materials such as metallic glasses and polymers, but their impact on hybrid glasses has yet to be explored. In this study, we examine the size-dependent vitrification behavior of hybrid glasses using fast scanning calorimetry across a broad range of heating and cooling rates. Our results are similar to that observed in polymer and metallic glasses, the glass transition temperature (T_g) is not significantly influenced by sample size at the micro-meter scale at cooling rates larger than or equal to 30 K/s. Furthermore, the vitrification enthalpy displays a clear dependence on sample size, with smaller samples exhibiting a larger overshoot enthalpy, which is attributed to a reduction of fictive temperature values (T_f) with size. These features originate from the network structure and flexibility of coordination bonding. Our findings suggest that the vitrification enthalpy is more fundamental than the temperature in size effects and that the low enthalpy state of smaller hybrid glass samples has implications for their functional properties.

Quantum computers leverage the unique advantages of quantum mechanics to achieve acceleration over classical computers for certain problems. Currently, various quantum simulators provide powerful tools for researchers, but simulating quantum evolution with these simulators often incurs high time costs. Additionally, resource consumption grows exponentially as the number of quantum bits increases. To address this issue, our research aims to utilize Large Language Models (LLMs) to simulate quantum circuits. This paper details the process of constructing 1-qubit and 2-qubit quantum simulator models, extending to multiple qubits, and ultimately implementing a 3-qubit example. Our study demonstrates that LLMs can effectively learn and predict the evolution patterns among quantum bits, with minimal error compared to the theoretical output states. Even when dealing with quantum circuits comprising an exponential number of quantum gates, LLMs remain computationally efficient. Overall, our results highlight the potential of LLMs to predict the outputs of complex quantum dynamics, achieving speeds far surpassing those required to run the same process on a quantum computer. This finding provides new insights and tools for applying machine learning methods in the field of quantum computing.