The study of cavity quantum electrodynamics based on optical microcavities and solid-state quantum systems such as quantum emitters and quantum spin systems are widely applied to modern quantum optics and quantum information science. In recent years, the study of the interaction between plasmonic nanocavity with mode volume beyond diffraction limit and high-performance two-dimensional (2D) semiconductor excitons receives extensive attention, and it is expected that such cavity-exciton system can be applied to integrated quantum optical systems. The study first introduces the weak and strong coupling between plasmonic nanocavities and 2D semiconductor excitons, and summarizes the modulation of excitonic spin-valley photonics of 2D semiconductor excitons and the coupling at the nanoscale. Then, the coupling of the nanocavity with the 2D single defective quantum emitter is introduced, demonstrating the potential application of such system in future integrated nano-optoelectronics. Finally, the challenges and opportunities for the study of plasmonic nanocavities and low-dimensional exciton systems are discussed.

Single-photon sources in solid-state materials are a class of quantum light source that generate single-photon radiation through point defects or excitons in solid-state materials. Due to advantages such as high stability, ease of operation, high integrability, and high efficiency, the single-photon source has a wide application prospect in fields such as quantum information processing, quantum sensing, and quantum optics. First, the research systematically classifies different types of single-photon sources in novel solid-state materials, compares their respective advantages and limitations. Furthermore, it focuses on common strategies for modulating the performance of single-photon sources, such as strain engineering, temperature control, electric field tuning, and surface plasmon coupling. Additionally, the latest progress and challenges in integrating single-photon sources in novel solid-state materials into photonic chips are discussed, along with application examples in quantum communication, quantum computing, and quantum key distribution. Finally, current issues and future development directions in this research field are summarized, aiming to provide a comprehensive and concise overview of single-photon sources in novel solid-state materials.

Quantum computing, which leverages fundamental principles of quantum mechanics such as quantum superposition and quantum entanglement to process information and perform computations, holds immense potential for various applications and developments. However, its physical implementation is currently plagued by substantial challenges. Recently, the fusion-based quantum computing scheme has garnered considerable attention. This scheme relies on periodically generated resource states, linking them into a fusion network via fusion measurements to achieve high fault-tolerant efficiency. This study introduces the fundamental principles, fault-tolerant performance, and resource state generation schemes of fusion-based quantum computing. Finally, we discuss future developments in hardware implementation and fault-tolerant efficiency.

Hybrid quantum systems have emerged as a key platform for promoting breakthroughs of quantum technology and sustainable development of quantum science. Cavity optomechanical systems, with their high integrability and strong tunability, show significant application values in fields such as electro-optomechanical transduction, quantum state preparation, and quantum precision metrology. It is hailed as a milestone in the history of photonics by Nature. Recent advances in laser cooling and micro/nanofabrication techniques have significantly enhanced the ability to manipulate and observe microscopic quantum systems such as atoms, photons, and electrons, facilitating the measurement technique transition from classical sensitivity limits to quantum effect-based supersensitive sensing, achieving exponential performance gains. Here, we review the latest advances in quantum squeezing-enhanced quantum sensing performances, emphasizing the key advantages of quantum compression in achieving ultra-sensitive quantum sensing. From a broader perspective, leveraging squeezing-enhanced supersensitive quantum sensing provides a promising path for improving performance in gravitational-wave detection, dark-matter searches, quantum illumination, and biomolecular tracking.

Two-dimensional (2D) materials exhibit novel physical properties such as large exciton binding energy and the ability to be assembled as heterostructures. With the continuous development of 2D materials, their devices have shown significant potential in fileds such as optoelectronics, quantum information, and nanotechnology. Micro/nano-photonic cavities enable control of light-matter interactions at micro/nano-scale dimensions, offering an ideal platform for studying the exciton-photon coupling in the quantum regime. Consequently, the integration of 2D materials with micro/nano-photonic cavities has garnered considerable interest. This review summarizes representative devices that facilitate coupling between 2D materials and micro/nano-photonic cavities, with a focus on quasiparticle interactions and control in multiple degrees of freedom. By designing and manipulating these coupled systems, researchers can explore novel quantum phenomena such as exciton-photon polaritons and exciton-nanocavity coupling in the phononic degrees of freedom. The rich quantum effects observed in such systems demonstrate their notable potential for applications in quantum sources, nonlinear optics, and topological photonics. Despite challenges related to preparation and integration processes, and theoretical complexities involving strong correlations and many-body effects, the rapid progress in 2D material-micro/nano-photonic cavity coupling systems is opening new avenues for advancing quantum photonic technologies.

Chirality, a fundamental property of substances, is widely present in physical, chemical, and biological systems. Recent studies have made considerable progress on chiral interactions between light and matter, thereby opening up new research directions for quantum optics and information technology. In chiral interactions, the polarization state of the localized light field is closely associated with its propagation direction, thereby achieving nonreciprocal light-matter coupling. This phenomenon breaks through the fundamental assumption of time-reversal symmetry in traditional quantum optics. Consequently, it has yielded a series of novel chiral quantum optical platforms and technologies, including chiral quantum state transfer, deterministic spin photon interfaces, and complex quantum network construction. These advances not only promote the development of multi-quantum state superposition manipulation and direction-dependent state storage technology but also facilitate significant breakthroughs in fields such as quantum communication, computing, and simulation. However, the widespread application of chiral quantum optics is still plagued by several challenges. For example, the designing of efficient chiral interfaces, suppression of photon loss, and characterization of chiral interactions in complex systems are certain major issues that need urgent attention. This article reviews the latest research progress on chiral quantum optics and its applications in quantum information science. Furthermore, the possible future development directions and their potential impacts are explored in detail.

Quantum precision measurement refers to the utilization of quantum resources to achieve high-precision physical quantity measurements that surpass classical limits. Among these technologies, high-precision quantum sensors such as atomic clocks and atomic magnetometers, which are implemented through the manipulation of atomic spin states, can detect minute frequency or magnetic-field variations. Spin-squeezed states have garnered significant attention as a crucial quantum resource owing to their application in enhancing measurement sensitivity. This study systematically introduces three preparation methods for spin-squeezed states based on distinct physical mechanisms, reviews important research advancements in entanglement-enhanced quantum metrology, and presents prospects for future directions in entanglement-enhanced measurement technologies based on the rapidly developing field of programmable quantum many-body systems in recent years.

In recent years, photonic chips have emerged as a significant direction in the development of photonics due to their characteristics of large-scale integration, low cost, low power consumption, and fast response. Lithium niobate is considered as a promising material for photonic chips because of its large second-order nonlinear coefficient, strong electro-optic effect, and other properties. A crucial challenge for the application of lithium niobate photonic chips is the interface between optical fibers and photonic chips. Grating couplers have become an important solution to the fiber-to-chip coupling problem due to their high flexibility, large misalignment tolerance, and ease of fabrication. This paper reviews recent research progress on thin-film lithium niobate grating couplers, summarizes several approaches to enhance their performance, and provides perspectives on their future development.

As an important research tool of quantum technology, acoustic quantum states in the optomechanical system play an important role in quantum communication, quantum computing, precision measurement, and other fields. This paper reviews the development of acoustic quantum states in the optomechanical system, including the basic physical process of the optoacoustic interaction, the generation and regulation of acoustic quantum states in the optomechanical system, and focuses on the research progress of acoustic quantum states in the application direction of microwave-optical conversion, on-chip information processing, precision measurement, and hybrid systems, as well as the advantages and challenges associated with each direction. Finally, the future development direction of acoustic quantum states in optomechanical crystals is discussed, including discovering more optomechanical coupling mechanisms, increasing the intensity of optomechanical coupling, breaking the quantum limit, large-scale integrated device preparation, and expanding more applications with more other systems.

Quantum steering represents a significant resource in quantum mechanics, manifesting as a non-classical correlation positioned between quantum entanglement and Bell nonlocality. Its distinctive asymmetric properties and substantial research implications span both fundamental physics and applied science. This paper presents a comprehensive overview of the fundamental characteristics, current developments, and emerging trends in quantum steering research. Through an examination of quantum steering in discrete and continuous variables across various degrees of freedom, the paper elucidates its extensive physical implications. Analysis of high-dimensional quantum steering characteristics demonstrates its robust resistance to noise interference. The investigation of quantum steering applications encompasses quantum networks, one-sided device-independent quantum key distribution, quantum random number generation, and quantum communication, highlighting its substantial potential for future quantum industry development. As quantum technology advances and incorporates interdisciplinary approaches, particularly artificial intelligence, quantum steering is positioned to serve as a crucial driver in the evolution of quantum information technology and its industrial applications.

One of the most prominent features of quantum physics is the existence of quantum correlations between different quantum systems, which are not equivalent to quantum entanglement. Although quantum entanglement has long been regarded as the primary manifestation of quantum correlations, Ollivier and Zurek introduced the concept of quantum discord in 2002, highlighting that quantum correlations can also exist between subsystems in zero-entanglement systems. Unlike in classical information theory, the overall information of a quantum system cannot be simply described as the sum of the information of its subsystems. In this paper, we review the fundamental theory and calculation methods of quantum discord, with a particular focus on its applications in quantum information processing. In addition, we analyze the role of quantum discord in quantum teleportation, showing that quantum discord exhibits strong robustness against decoherence and noise, providing crucial resources for quantum information processing.

Quantum key distribution (QKD), based on quantum mechanical principles, provides a secure key agreement method for remote users and represents one of the most practical technologies in quantum information science. Integrated photonics offers an ideal technological platform for implementing QKD, demonstrating significant advantages in system scale, cost control, integration density, and scalability. This study focuses on integrated optical QKD, providing an overview of commonly used integrated optical material platforms and fundamental functional devices. Emphasizing practical system design and implementation, we summarize representative achievements in integrated QKD and analyze in-depth security issues of integrated QKD devices and systems. Additionally, we present perspectives on the development of quantum communication networks based on integrated devices.

Quantum information technology is an emerging discipline that combines quantum mechanics with information science, promising revolutionary advancements in computing, communication, and precision measurement. Optical quantum systems, known for their low transmission loss and low-noise coupling at room temperature, are crucial components of quantum information technology. To effectively utilize the low noise and strong quantum correlation properties of optical quantum systems, phase-locked control technology is widely applied in quantum state generation, mode regulation, and quantum state detection. This article reviews the research progress in phase-locked control technology within the field of optical quantum information field, including the principles of the technology, its typical applications in optical quantum information systems, and implementation schemes under weak light intensity conditions, and prospects for future development directions.

Photon blockade is a fundamental nonlinear phenomenon in cavity quantum electrodynamics, enabling deterministic control over single photon or photon streams by suppressing multiphoton excitations. This effect provides a crucial physical mechanism for advancing quantum information science. Current research primarily focuses on two major mechanisms: conventional photon blockade and unconventional photon blockade. The former relies on strong atom-cavity coupling, which induces anharmonic energy level splitting and inhibits multiphoton transitions via spectral nonuniformity. In contrast, the latter exploits destructive quantum interference between multiple excitation pathways, achieving two-photon excitation suppression even under weak coupling conditions, thereby significantly reducing the requirement for strong nonlinearity. The interplay between these mechanisms can further optimize photon blockade performance and greatly enhance its efficiency. In recent years, research has extended into new directions such as nonreciprocal photon blockade and nonlinear dissipation control. These developments not only provide a richer theoretical framework for understanding nonlinear behaviors in quantum optics but also establish technical foundations for quantum information processing, quantum computing, and quantum precision measurements. Additionally, research on multi-photon blockade and its extended mechanisms offers crucial support for developing multi-photon quantum technologies. This review systematically summarizes the implementation schemes and recent progress of single-photon and multiphoton blockade, as well as their extensions. It also highlights their potential applications in single-photon sources, quantum information processing, and quantum networks. Finally, we discuss prospective research directions in the field of photon blockade, including the exploration of novel unconventional blockade mechanisms and their integration into large-scale quantum information systems.

With the rapid development of quantum algorithms and quantum computers, classical cryptography is facing potential security threats. Quantum key distribution (QKD) has become a core solution to address this challenge as a key technology for information-theoretic security. High-dimensional quantum key distribution (HD-QKD) has rapidly emerged as an important research direction in QKD field with its higher information capacity and stronger noise resilience. In recent years, HD-QKD has been widely applied to various photonic degrees of freedom. This paper reviews the latest developments in HD-QKD technology, emphasizes the experimental achievements of different degrees of freedom in HD-QKD. Additionally, it analyzes the challenges associated with these degrees of freedom and explores the future development directions of HD-QKD.

Airborne platforms serve as an essential link in promoting the space-air-ground integrated wide-area optical/quantum communication network. However, when airborne platforms operate at high speeds, aero-optical effects cause beam deviation, jitter, blur, energy attenuation, and other phenomena that affect the performance of optical/quantum communication systems. To begin, this paper delves into the study of aero-optical effects, and the effects of aero-optics on airborne optical communication are described and analyzed in terms of three aspects: the increased burden on the pointing, acquisition, and tracking system; interruption of the communication link; and decrease of communication quality. In addition, the beam shifts, increased transmission loss, and key rate degradation caused by aero-optical effects in several airborne quantum key distribution scenarios are presented. Finally, the challenges faced by airborne optical/quantum communication systems in transmission link optimization, system performance evaluation, and compensation method design are summarized, and the prospects for development in this field are outlined.

Non-Hermitian systems have recently garnered widespread attention. Some non-Hermitian systems that satisfy parity-time reversal symmetry may possess real eigenenergy spectra and can be used to describe open systems with loss and gain. Their eigenenergy spectra exhibit strong nonlinear responses to external perturbations near exceptional points, which is a characteristic that can be harnessed to design implementations for quantum metrology and quantum sensing. Quantum-parameter estimation theory, which uses the quantum Fisher information, provides the quantum Cramér-Rao lower bound for parameter estimation, which sets a limit on the sensitivity of quantum measurements and sensing. Additionally, quantum-parameter estimation theory guides the search for optimal measurement schemes, and some optimal measurement results can be achieved within the quantum Cramér-Rao bound. In schemes that leverage the advantages of quantum resources, such as quantum entanglement, the estimation precision can surpass the standard quantum limit and reach the Heisenberg scaling. Additionally, some non-Hermitian systems may demonstrate enhanced sensitivity to external perturbations without involving exceptional points owing to their non-Hermitian nature, thus allowing non-Hermitian sensing schemes to be realized. This review introduces the research and progress in quantum metrology and sensing based on non-Hermitian systems.

The spin-exchange relaxation-free (SERF) state effect has been used to develop high-performance atomic magnetometers and atomic gyroscopes. Under the conditions of high-atomic number density and a zero-magnetic-field environment, alkali metal atoms enter the SERF state because the frequency of their spin-exchange collisions is much greater than the Larmor precession frequency. This results in a major reduction or even elimination of the atomic spin-exchange relaxation, and the linewidth of the atomic magnetic resonance becomes narrower. Heating the alkali metal atom vapor cell and shielding or compensating magnetic fields are key technologies used to attain the SERF state. To achieve a zero-magnetic-field environment, two methods are typically adopted: passive shielding the geomagnetic field with high-permeability materials, or active compensation of the ambient magnetic field with three-axis coils. This study elucidates the physical mechanism underlying the SERF effect, provides an in-depth examination of current techniques for achieving a zero-magnetic-field environment, and offers a comparative analysis of three approaches, namely passive shielding, active compensation, and an approach combining both. Additionally, this study provides technological prospects for achieving zero-magnetic-field environments.

Nitrogen-vacancy (NV) color centers in diamond have important applications in quantum sensing and precision measurement owing to their unique photoluminescence and electron spin resonance properties. Through the integration of NV color centers as quantum sensors at the probe tip coupled with the combination of confocal and scanning probe technologies, this study designs a scanning microscopy system based on these centers. This method successfully breaks through the bottleneck of micro magnetic imaging required for detecting magnetic materials. This system was used to perform magnetic imaging of iron oxide samples, revealing their microscopic magnetic domain structure. Based on a comparative analysis with magnetic field microscopy imaging results, the advantages of scanning NV microscopy in microscopic magnetic imaging are demonstrated. Therefore, based on this study, future research can focus on the micro magnetic detection of two-dimensional iron oxide materials and their applications in catalysis and other fields.

Quantum entanglement swapping plays a crucial role in quantum communication by enabling entanglement establishment between two particles that have never directly interacted. For bipartite continuous-variable system, the entanglement characteristics are typically witnessed by the positivity under the partial transposition (PPT) criterion. The entanglement degree is inversely related to the smallest symplectic eigenvalue of covariance matrices-smaller values indicate stronger entanglement. This study theoretically investigates the impact of optical loss on all-optical entanglement swapping by introducing vacuum fields through beam splitters placed in light beam transmission paths to simulate experimental losses. Through theoretical calculations, we found that the all-optical channel between Claire and Bob of all-optical entanglement swapping is highly loss resistant. This work is of great significance for promoting the practical application of all-optical entanglement swapping in quantum network construction.

An intensity-differential squeezed state optical field prepared via four-wave mixing in a cesium atomic ensemble offers advantages such as wavelength matching with cesium atomic transition lines and a spatial multimode structure. This renders it valuable for quantum information applications. However, achieving high-compression-state optical fields through four-wave mixing in cesium atoms typically requires high pump light power and atomic pool temperature, thereby limiting its practicality. This study combines a six-mirror ring optical resonant cavity and a cesium atomic ensemble to achieve a single resonance of the pump light within the cavity while allowing the probe and conjugate lights to pass through in a single pass. This configuration improves pump light utilization and achieves cavity-enhanced cesium atomic four-wave mixing. Consequently, the required pump light power and atomic pool temperature are considerably reduced. Experimental results show that at an intensity-difference compression degree of -6 dB, compared to cavity-free four-wave mixing, the cavity-enhanced four-wave mixing reduces the required pump light power from 600 mW to 340 mW and the atomic cell temperature from 109 ℃ to 98 ℃. These findings offer a new solution for developing low-power, spatially multimode quantum light sources. Further, they are crucial for advancing the application of four-wave mixing in atomic ensembles.

The study investigates the enhancement of quantum key rate in discrete-modulation continuous-variable quantum key distribution (DM-CV-QKD) systems over satellite-ground links through the use of optical amplifiers, and its impact on system security. Simulation analysis reveals that optical amplifiers can significantly boost the quantum key rate for short-distance communication. Although 4-ary QKD and 8-ary QKD protocols effectively improve key rate in this scenario, their relatively large degradation regions fail to cover the secure communication distance between satellites and the ground, resulting in a limited secure communication range. To break through this limitation, a novel 16-ary double-ring modulation scheme for DM-CV-QKD is introduced, which effectively reduces the degradation region and enhances the overall system reliability, thereby significantly improving both the key rate and secure communication distance. Finally, the study also analyzes the effects of factors such as turbulence strength, optical wavelength, and horizontal elevation angle on system performance. The results show that under strong turbulence conditions, the Gaussian modulation and the 16-ary double-ring modulation scheme can still effectively improve signal quality with optical amplifiers, and their enhancement region can cover the operational range of low-earth orbit satellites, demonstrating their application value and significance in complex environments.

A scheme is proposed to explore the absorption and susceptibility of hybrid quantum systems comprising superconducting qubits and two mechanical resonators. The results show that the transparency based on mechanically induced coherent population oscillation (MICPO) can be tuned by the Rabi frequency and decay rate of the mechanical resonator. We also demonstrate that the coupling strength between the two mechanical resonators can be detected by measuring the distance between two peaks in the probe spectrum. We also propose a new scheme for measuring the frequency of mechanical resonators. This study is of great significance in the fields of precision measurement and quantum information processing.

This article investigates a hybrid cavity magnetic-cavity optomechanical system incorporating an optical parametric amplifier, examining its multi-window transparency phenomenon and fast-slow light conversion effect. The characteristics of the output field are analyzed through the dynamic evolution of the system Hamiltonian and the input-output field relationships. Numerical simulations reveal that distinct transparency windows emerge through the sequential introduction of cavity-magnetic coupling, effective magnetic-phonon coupling, cavity-cavity coupling, and effective optomechanical coupling. The transparency windows can be precisely controlled by modulating the coupling strength. The incorporation of optical parametric amplifiers enhances the peak amplitude on the right side of the absorption spectrum, enabling specific regulation of magnetically induced transparency. Furthermore, investigation of the system group delay effect, induced by various coupling mechanisms and optical parameter amplifier gains, demonstrates the capability for conversion between fast and slow light propagation.