Science China Physics, Mechanics & Astronomy最新文献

Complex numbers are theoretically proved and experimentally confirmed as necessary in quantum mechanics and quantum information, and a resource theory of imaginarity of quantum states has been established. In this work, we establish a framework to quantify the imaginarity of quantum operations from the perspective of the ability to create or detect imaginarity, following the idea by Theurer et al. (Phys. Rev. Lett. 122, 190405 (2019)) used in coherence theory. We introduce two types of imaginarity measures of quantum operations based on the norm and the weight, investigate their properties and relations, derive the analytical formulas of the measure under the trace norm for qubit unitary operations, and present some applications in the tasks of channel discrimination and the entanglement-assisted exclusion. The results provide new insights into the imaginarity of operations and deepen our understanding of dynamical imaginarity.

X-ray pulsars (XRPs) consist of a magnetized neutron star (NS) and an optical donor star. The NS accretes matter from the donor star, producing pulsed X-ray emission. In most cases, the donor stars are Be stars, and accretion is episodic, that is, the NSs are generally X-ray dim but occasionally experience outbursts. Here, we carry out a statistical study with the X-ray monitoring data and obtain strong correlations between the spin periods of the NSs and the outburst parameters for the first time. We show that XRPs containing faster rotating NSs tend to display more violent eruptions. In addition, pulsating ultraluminous X-ray sources in nearby galaxies follow a similar relationship. We demonstrate that most of these systems are close to the spin equilibrium, and that brighter pulsars have acquired more angular momentum by accreting matter from their companion stars, resulting in faster rotating NSs.

Non-Hermitian (NH) systems can display exceptional topological defects without Hermitian counterparts, exemplified by exceptional rings in NH two-dimensional systems. However, exceptional topological features associated with higher-dimensional topological defects have only recently come into attention. We here investigate the topology of the singularities in an NH three-dimensional system. We find that the third-order singularities in the parameter space form an exceptional surface (ES), on which all three eigenstates and eigenenergies coalesce. Such an ES corresponds to a two-dimensional extension of a point-like synthetic tensor monopole. We quantify its topology with the Dixmier-Douady invariant, which measures the quantized flux associated with the synthetic tensor field. We further propose an experimentally feasible scheme for engineering such an NH model. Our results pave the way for investigations of exceptional topology associated with topological defects with more than one dimension.

Gravitational wave (GW) observations are expected to serve as a powerful and independent probe of the expansion history of the universe. By providing direct and calibration-free measurements of luminosity distances through waveform analysis, GWs provide a fundamentally different and potentially more robust approach to measuring cosmic-scale distances compared to traditional electromagnetic (EM) observations, which is known as the standard siren method. In this review, we present an overview of recent developments in GW standard siren cosmology, including up-to-date H₀ constraints: the re-analysis bright siren GW170817 (H_{0}=78.4_{-12.0}^{+25.7}text{km s}^{-1} text{Mpc}^{-1}) (employing the same methodology as the O4a dark and spectral siren studies), the most recent O4a dark-siren analysis (H_{0}=81.6_{-15.9}^{+21.5}text{km s}^{-1} text{Mpc}^{-1}), and their combination (H_{0}=76.6_{-9.5}^{+13.0}text{km s}^{-1} text{Mpc}^{-1}), and prospects for constraining cosmological parameters using future GW detections (H₀ is expected to be constrained to the sub-percent level in a 10-year observation of the third-generation GW detectors). We first introduce standard sirens based on how redshift information is obtained and outline the Bayesian framework used in cosmological parameter estimation. We then review the measurements on the Hubble constant from the LIGO-Virgo-KAGRA network and present the potential role of future standard siren observations in cosmological parameter estimations. A central focus of this review is the unique ability of GW observations to break cosmological parameter degeneracies inherent in the EM observations. Since the cosmological parameter degeneracy directions of GW and EM observations are quite different (roughly orthogonal in some cases), their combination can significantly improve constraints on cosmological parameters. This complementarity is expected to become one of the most critical advantages for GW standard siren cosmology. We also briefly highlight the impact of systematic uncertainties, such as detector calibration, weak lensing, peculiar velocities, and host-galaxy catalog completeness, and corresponding potential mitigation strategies, which currently limit the constraint precision of cosmological parameters. Looking forward, we highlight the importance of combining GW standard sirens with other emerging late-universe cosmological probes such as fast radio bursts, 21 cm intensity mapping, and strong gravitational lensing to forge a precise cosmological probe for exploring the late universe. Finally, we introduce the challenges and the role of machine learning in searching for more signals, ensuring reliable parameter inferences, and accelerating the inference process for cosmological parameters.

We investigate the implications of neutron star observations for understanding the origin of nucleon mass using a framework that combines three complementary approaches: the equation of state based on parity doublet structure for hadronic matter below 2n₀, the Nambu-Jona-Lasinio (NJL) model for quark matter above 5n₀, and integral constraints to minimize the ambiguities at the intermediate density region. By systematically exploring parameter spaces and comparing theoretical predictions with recent observational constraints, we establish constraints on the chiral invariant mass. Our results suggest that more than half of the nucleon mass originates from sources beyond spontaneous chiral symmetry breaking, challenging conventional understanding of nucleon mass generation. These constraints arise solely from fundamental physical principles and observational data, independent of specific assumptions about the nature of the quark-hadron transition, providing insights into the microscopic origin of hadron masses within a framework that combines a parity-doublet hadronic model with an NJL quark model.

For decades, efforts to shape acoustic waves focused on fixed metamaterials and static phase masks, leaving their internal state evolution largely untouchable. Here, we introduce an all-classical platform that unlocks real-time, Bloch sphere control of an acoustic two-level system, bringing the full arsenal of quantum-style coherent protocols to the realm of sound. Using a programmable electro-acoustic architecture, we implement independent and synchronized modulation of onsite detuning, coupling strength, and dissipation—enabling full Bloch-sphere trajectory steering. On this basis, we realize quantum-inspired control protocols including Rabi oscillations, Ramsey interference, Floquet modulation, and spin echo sequences, tracking amplitude and phase evolution of acoustic states in real time. Our approach establishes a new paradigm for wave-based control, bridging classical acoustics with quantum coherent protocols, and opens new opportunities for programmable sound field engineering, information storage, and analog simulation of gauge field dynamics.

The detection of gravitational waves (GWs) has opened a new window to test the fundamental nature of gravity. We present constraints on the nonstandard propagation of GWs using the spectral siren method applied to binary black hole (BBH) mergers from the third Gravitational-Wave Transient Catalog (GWTC-3). The spectral siren method exploits the redshift distribution of BBHs to probe the cosmic expansion history and break degeneracies between cosmology and modified gravity effects. We focus on the friction term v in the nonstandard GW propagation equation, which characterizes the running of the Planck mass. Assuming the standard ΛCDM cosmology, we find (nu=-1.1_{-1.1}^{+3.9}, nu=0.5_{-2.6}^{+3.5}) and (nu=0.7_{-2.3}^{+3.1}) (median and 90% credible interval) for the Truncated, Power Law + Peak, and Broken Power Law mass models, respectively. These results improve upon previous constraints from the bright siren event GW170817 by an order of magnitude, owing to the higher redshifts of BBHs in GWTC-3, which reach up to z ∼ 1. Our result suggests that the propagation of GWs is consistent with the predictions of general relativity, placing limits on modified gravity theories that predict a time-varying Planck mass. As the sensitivity of GW detectors improves, the spectral siren method will provide a powerful tool for testing gravity on cosmological scales and probing the physics of the early Universe.

The Chinese Space Station Survey Telescope (CSST) is an upcoming Stage-IV sky survey telescope, distinguished by its large field of view (FoV), high image quality, and multi-band observation capabilities. It can simultaneously conduct precise measurements of the Universe by performing multi-color photometric imaging and slitless spectroscopic surveys. The CSST is equipped with five scientific instruments, i.e., Multi-band Imaging and Slitless Spectroscopy Survey Camera (SC), Multi-Channel Imager (MCI), Integral Field Spectrograph (IFS), Cool Planet Imaging Coronagraph (CPI-C), and THz Spectrometer (TS). Using these instruments, CSST is expected to make significant contributions and discoveries across various astronomical fields, including cosmology, galaxies and active galactic nuclei (AGN), the Milky Way and nearby galaxies, stars, exoplanets, Solar System objects, astrometry, and transients and variable sources. This review aims to provide a comprehensive overview of the CSST instruments, observational capabilities, data products, and scientific potential.

The origin of supermassive black holes (SMBHs) is a pivotal problem in modern cosmology. This work explores the potential of the Taiji-TianQin space-borne gravitational-wave (GW) detector network to identify the formation channels of massive black hole binaries (MBHBs) at high redshifts (z ≳ 10). The network substantially improves detection capability, boosting the signal-to-noise ratio by a factor of 2.2–3.0 (1.06–1.14) relative to TianQin (Taiji) alone. It increases the detection rate of MBHBs formed from light seeds (LS) by more than 2.2 times and achieves over 96% detection efficiency for those originating from heavy seeds (HS). Furthermore, the network enables component mass estimation with relative uncertainties as low as ∼ 10⁻⁴ at the 2σ level. These improvements facilitate the assembly of a well-constrained population sample, allowing robust measurement of the fractional contributions from different formation pathways. The network achieves high precision in distinguishing between LS and HS origins (7.4% relative uncertainty at 2σ) and offers moderate discrimination between delay and no-delay channels in HS-origin binaries (24%). However, classification remains challenging for delay versus no-delay scenarios in LS-origin systems (58%) due to significant population overlap. In conclusion, the Taiji-TianQin network will serve as a powerful tool for unveiling the origins of SMBHs through GW population studies.

Chip-scale quantum magnetometers featuring both ultra-high sensitivity and uniform spin polarization are highly desired for practical applications and have been diligently pursued. However, the fulfillment of such capabilities for quantum magnetometers typically necessitates a separate heating unit, bulky reflector, and beyond, severely impeding on-chip integration and batch fabrication of these quantum devices. Herein, we present a novel paradigm for the wafer-level fabrication of ultra-sensitive chip-scale quantum magnetometer, which is enabled by integrating a highly reflective mirror and a temperature-controlled component on the optically transparent windows of the MEMS atomic vapor cell, thereby providing a genuinely all-in-one atomic vapor cell with a temperature stability better than ±5 mK at up to 200°C as well as a reflectivity of 95% at Rb D1 transition wavelength. With the as-developed on-chip atomic vapor cell with internal dimensions of Φ 3×1.5 mm³, we configured a chip-scale single-beam atomic magnetometer with a sensitivity floor of about 15 fT/Hz^1/2, along with a theoretically more homogeneous spin polarization distribution. We envision that the proposed chip-scale integration solution paves a concrete route for batch manufacturing and widespread application of quantum magnetometers.