Cavity optomechanics studies the interaction between photons and macroscopic mechanical oscillators. Now it has become an important field for the study of the transition between the quantum world and the classicalworld, as well as the non-classical and nonlinear effects. This paper first introduces some basic physical concepts in this field, including radiation pressure, optomechanical Hamiltonian, Heisenberg-Langevin equation, and linearization of equations. Then we review some progress of the novel optomechanical effects in recent years, including optomechanically induced transparency, nonreciprocal light propagation, high-order sideband generation, and optomechanical entanglement. Finally, some research prospects are proposed.

Recently molecules involving one or more Rydberg excitations have attracted considerable attention due to their unusual properties. Besides the exaggerated characteristics of the Rydberg atom (Rydberg atoms are highly excited atoms with principal quantum numbers n ranging from about ten upwards to several hundred.), such as small binding energies, large size, long lifetime, and huge polarizability, they possess abundant vibrational energy levels, exotic adiabatic potentials, permanent electric dipole moments and sensitivity to external fields, which make them not only include the excellent properties of the Rydberg atom, but also have been widely used in quantum information storage, quantum simulation, and evenmedicine, which has strongly aroused the research interest of scholars at home and abroad. According to the different binding mechanisms, Rydberg atoms can generally form three types of Rydberg molecules. The first type of Rydberg molecules is formed by two Rydberg atoms that interact via long-range electrostatic multipole interactions, often referred to as Rydberg macrodimers. Another class of Rydberg molecules is a bound state between ground-state and Rydberg-excited atoms. Its binding mechanism is a result of attractive interaction induced by the low-energy scattering of a Rydberg electron from an atom with a negative scattering length, and is often described by the Fermi pseudopotential model. The third type of Rydberg molecules is formed through long-range electric-multipole interaction between the Rydberg atoms and pointlike positive ions. Similar to the Rydberg macrodimers, the adiabatic potential energy curves of Rydberg molecules arise from nonperturbative solutions of the atom-ion interaction Hamiltonian. In this paper, we review the theoretical and experimental research progress of diatomic Rydberg molecules in recent years, including the formation mechanisms of different types of Rydberg molecules, experimental observations, and the study of their spectral properties, which will provide references for researchers who are engaged in or will be engaged in Rydberg molecules, and provide a theoretical and experimental basis for further study of Rydberg molecules.

Nonclassical light fields with a property of strong antibunching are important resources for quantum information and quantum optics. Based on the quantum interference effect of nonlinear optics, a strong antibunching light can be obtained by superposing the squeezed vacuum state and the coherent state of a specific phase on an optical beam splitter. Squeezing degree and displacement can be independent adjustments for optimal antibunching. In this paper, combined with the parameters of the experiment system, we have theoretically studied the influence of the squeezing degree of the squeezed vacuum state and the amplitude of the coherence state on the generating of an antibunching light. Under the optimal displacement condition, analyzed the influence of the measurement of g20 of the antibunching light with system total efficiencies、background noises、Hanbury Brown-Twiss (HBT) and Double HBT measurement method. Discussed the value of g20 and average photon rate of the quantum state where the error is 0.

In this paper, quantum entanglement and quantum coherence in the XXZ Heisenberg spin chain with three-site interaction are investigated. We employ concurrence and relative entropy to measure quantum entanglement and quantum coherence. The influence of XZX+YZY three-site interaction, XZY-YZX three-site interaction, and magnetic field on the concurrence and the relative entropy vary with temperature are mainly studied. It is found that there is no sudden death phenomena in quantum coherence, and the temperature range of quantum coherence is larger than that of quantum entanglement. In addition, at absolute zero temperature, quantum coherence can characterize the quantum phase transition phenomena. In the ferromagnetic case, increasing XZX+YZY three-site interaction is the most effective way to reduce the attenuation rate and enlarge the temperature range of quantum coherence. Nevertheless, in the anti-ferromagnetic case, the cooperation effect of XZX+YZY and XZY-YZX three-site interaction can increase the maximum quantum coherence significantly and retard its decay rate at zero magnetic field. Additionally, in ferromagnetic and anti-ferromagnetic cases, when magnetic field B<0, the temperature range of quantum coherence is increased obviously, which is beneficial to preserve nonzero quantum coherence.

Broadband photodetectors play a significant role in quantum optics and quantum information processing including the detection of squeezed pulses, quantum state reconstruction, and continuous-variable quantum key distribution system. By the noise analysis model of the photodetector based on transimpedance amplifier circuit, the electronic noise and signal noise characteristics are theoretically analyzed. And based on the PSpice simulation model, the effects of themain parameters on the performance of the photodetector are analyzed in detail. The input voltage noise of the operational amplifier is the main noise source of electronic noise, and the current noise of the operational amplifier affects the magnitude ofthe low-frequency noise. The input parasite capacitances play a non-negligible influence on the noise power spectrum. With the increase of the input parasitic capacitance, the electronic noise increases and the signal-to-noise ratio decreases. Through the comparisons between the theoretical calculation and the simulation results, these two analysis methods are equivalent. A wideband photodetector is developed by using a low-noise operational amplifier of OPA847. The experimental noise power spectrum is in good agreement with the simulation results, and the -3 dB bandwidth of the photodetector is 110 MHz.

Quantum Fisher information is a key conception of precision measurement, which determines the precision of the established parameter. In this paper, we give an expression for the quantum Fisher information flow utilizing right logarithmic derivative for open quantum systems and apply it to a two-level system coupled to a non-Markovian environment characterized by Lorentzian spectral density. Discussion of the relation between the sign of quantum Fisher informationflow and the non-Markovianity has been made. In addition, we find the quantum Fisher information flow and the quantum Fisher information show similar behavior. The reason behind this similarity is the null eigenvalue of the density matrix.

The quantum random number plays an increasingly important role in information security because of its unpredictability and true randomness. Most of the existing random number generation protocols assume that the light source obeys a certain distribution probability and then estimates the minimum entropy of random number extraction from the measured value. However, due to the imperfections of the actual light source devices, the distribution of light intensity fluctuates to some extent. If the intensity fluctuation is ignored in the process of calculating the minimum entropy, the calculated minimum entropy value will be too large and the safety will be affected. If the traditional method is used to consider the fluctuation of light intensity, the estimation result will be too poor and the size of the randomness that can be obtained will be reduced. In order to solve this problem, this paper proposes a quantum random number generator with a light source monitoring function, and takes the self-testing quantum random number generator protocol based on dimension witness value as an example. Simulation results show that by adding a light source monitoring module at the source part, the upper and lower bounds of the single-photon contribution can be more tightly estimated, and higher minimum entropy and randomness can be obtained compared with the traditional method. This scheme provides a useful tool for the practical application of the quantum random number generator.

Quantum repeater is important for long-distance quantum communication and scalable quantum network. The basic idea of quantum repeater scheme is to divide the long-distance transmission channel into several shorter sub-channels and extend the entanglement to the whole transmission channel through the entanglement swap between two adjacent sub-channels. Duan-Lukin-Cirac-Zoller (DLCZ) protocol is a long-distance entanglement distribution scheme that has been widelystudied in recent years. The core of DLCZ protocol is the spontaneous Raman scattering process, which produces a photon and an associated spin-wave excitation with a certain probability. The entanglement lifetime is one of the key parameters of a quantumentanglement interface in the experiment of atom-photon entanglement. Although storage lifetime based on magnetic field insensitive spin-wave atom-photon entanglement has reached the order of milliseconds, there is no report on long-lived atom-photon entanglement source based on magnetic field-sensitive spin-wave till now. Based on the above research background, we place the 87Rb cold atomic ensemble in a polarization interferometer formed by a pair of beam displacers, which encode two spatialmodes of a photon associated with magnetic field sensitive spin waves generated by spontaneous Raman scattering process into a polarization qubit, realizing a long-lived atom-photon entanglement source based on magnetic field sensitive spin-wave. The storage lifetime of a magnetic field sensitive entanglement source is mainly affected by magnetic field noise and atomic motion. The effect of atomic motion is minimized by increasing the spin-wave wavelength through decreasing the angle between the write-read light and Stokes-anti-Stokes photon detection directions. The influence of magnetic field noise is minimized by accurately compensating for environmental magnetic field by utilizing retrieval efficiency as a reference. The entanglement source lifetime reaches 900?s, the Bell parameter S=2.58±0.03, which violates the Bell inequality by 19.3 standard deviations. This work enriched the study of atom-photon quantum interfaces and provided the foundation for the realization of long-distance quantum communication.

Based on the fractional cubic-quintic nonlinear Schrdinger equation, the interaction characteristics of chirped double Airy beams are numerically studied. The results show that breathing solitons or mutually repulsive solitons are formed under the effect of fractional diffraction and initial chirp when the initial interval between two in-phase Airy beams is zero. Airy beams attract each other to produce quasi-stable transmission of respiratory solitons, while mutual repulsion forms a pair of solitons with increased lateral spacing. The larger the absolute value of the initial chirp, the stronger the repulsive force between the two Airy beams and the larger deflection angle of the beam evolution when the initial interval is not zero. As the Lévy index increases, the beam width and the width of the soliton pair increase under the fractional diffraction effect. When the initial input is two antiphase Airy beams, the interaction is generally repulsive. The larger the initial chirp, the stronger the repulsive force between two airy beams. This work may provide new control methods for the interaction of Airy beams. We study theoretically and numerically the interaction of chirped Airy beams simulated by fractional nonlinear cubic and quintic Schrdinger equation. By considering the fractional diffraction effect, Airy beams without initial chirp exhibit damped oscillations in the propagation range. The Lévy index is smaller, and the oscillation characteristic is more obvious. When the initial chirp exists, the secondary chirp can affect the strength of the fractional effect and nonlinear effect. The Lévy index is the larger, fractional and nonlinear effects are more sensitive to the secondary chirp. The stably transmitted breathing soliton is generated by beam attraction and the symmetric breathing soliton pairs are generated by beam repulsion. The secondary chirp only affects the transmission of the second beam. This work may provide new control methods for the interaction of Airy beams.

Since the beginning of the 21st century, cloud computing, big data and artificial intelligence have swept the world. The explosive growth of information has made stable communication with low delay, high speed, large capacity, easy to access become the development trend. However, the existing medium and low frequency spectrum resources are tight and the frequency band is crowded, which is not enough to meet the needs of communication. The high frequency band, especially the millimeter wave band, is rich in spectrum resources and meets the needs of a high signal transmission rate. Therefore, the working frequency of the signal is developing towards high frequency microwave or even millimeter wave band. Due to the "rate bottleneck" of electronic devices, it is difficult to generate and transmit high-frequency millimeter wave signals based on traditional electrical methods. The development of microwave photonics provides a new way for the generation, processing and transmission of high-frequency millimeter wave signals. Combining the advantages of optical fiber communication and wireless communication, the radio over fiber (ROF) technology provides great convenience for mass access and wireless transmission at present, and has broad application prospects. High frequency factor millimeter-wave technology based on external modulator is one of the most promising millimeter-wave generation technologies, in the field of microwave photonics, which can realize the transformation from low frequency RF driving signal to high frequency millimeter-wave signal. In order to improve the frequency doubling coefficient and reduce the complexity of the system of the millimeter-wave signal generation in the radio over fiber, a 24-frequency millimeter wave optical wireless communication system based on the combination of cascaded dual-drive Mach Zehnder modulator (DMZM) and high nonlinear fiber (HNLF) is proposed. By adjusting the parameters, the two modulators work at the maximum biaspoint to generate the fourth-order optical sideband with pure spectrum. The data signal is loaded into the 4-order optical sideband by means of single-sideband modulation, and then the two sides are coupled and transmitted. The 12-order optical sideband is obtained by the four-wave mixing effect of HNLF and the filtering of the cross multiplexer. Finally, the high quality 24-tupling millimeter-wave signal is generated by photodetector (PD) beat frequency. In addition, the working principle of the system is analyzed in detail, and the influence of the length of HNLF, the incoming optical power and the standard linear optical fiber on the system performance is verified by simulation. The simulation results show that when the system is in error-free transmission, the power cost of back-to-back (BTB) transmission and 30 km fiber transmission is 2.5 dB. This scheme has the advantages of a simple structure, high frequency doubling coefficient, insensitive polarization and good performance. In addition, it avoids the use of active device SOA, further reduces the experimental cost and improves the system efficiency, which provides a theoretical reference for the actual construction of ROF system, and provides a new way for the development of microwave photonics.

As a quasiparticle formed by light and conduction electrons in graphene, surface plasmon polaritons (SPPs) due to their tight confinement to light and long propagation distances are promising for developing quantum interconnect devices. However, the significant damping of SPPs in the material generally causes the loss of quantum information, which greatly hinders its application. We here propose a mechanism to overcome the destructive effect of the damping SPP on the dynamics of a quantum emitter (QE). Via investigating the near-field coupling between QE and the SPP in a graphene nanodisk, we find that, with the complete dissipation of the QE efficiently avoided, quantum information of QE can be stabilized even toits steady state. This is caused by that, with decreasing the QE-graphene distance, the QE becomes so hybridized with the SPP that one bound state is formed between them. Our result supplies a useful way to avoid the impact of SPPs damping, which lays a foundation for developing quantum polaritonic devices.

In recent years, nitrogen vacancy (NV) centers in diamonds have been widely and intensively investigated due to their unique solid-state spin system, excellent ultra-high magnetic sensitivity, spatial resolution, long decoherence time and fluorescence stability. Based on the long spin coherence time and manipulable and readable electron spin states of NV centers, it is regarded as one of the most promising quantum sensor materials for quantum computing, weak signal (magnetic and electric field) detection and temperature measurement, and shows great potential for applications in quantum sensor research. This paper focuses on the study of modular magnetometer based on diamond NV centers. The crystal structure and energy leap properties of the NV centers, the quantum manipulation principle of the magnetometers, and the solution to the problems of the traditional fluorescence spectral acquisition system and optically detected magnetic resonance (ODMR) spectral acquisition systems, such as cumbersome construction, the low focusing accuracy of the detected samples, difficulty in the conversion between the acquisition systems, and the ODMR spectral acquisition signal, are introduced. We designed an optical fiber sensing-based fluorescence acquisition and ODMR spectral acquisition conversion system to address the problems of low signal-to-noise ratio and low acquisition accuracy of ODMR spectral acquisition. The system is designed to integrate the excitation light source circuit, microwave sensing antenna, fiber optic sensor, microscope focusing optical path, PD (photodetector) amplification circuit, signal processing module and fluorescence spectrometer modules through fiber optics, which provides hardware support for the software part of signal processing. In the software part, the signal data processing and spectral imaging functions are realized by open-source programming. After the initial processing of the data by the PD amplifier circuit, the data are further processed by the signal processing module in the software part, and the data are presented in the form of a spectrum, and the final magnetic sensitivity reaches 0.51nT/Hz1/2.