Space gravitational wave detection is oriented to gravitational wave signals in 0.1 mHz～1 Hz band, which contains wave source information of larger characteristic mass and scale. The current space gravitational wave detection plans use large laser interferometer devices to detect, in which the sensitivity of key components, such as the laser light source system and the drag-free system, depends on extremely low electrical noise, which is limited by thenoise level of the voltage reference source on the spacecraft. Therefore, it is necessary to develop low noise voltage reference and perform low-frequency noise characterization of laser intensity noise and electrical noise of key electrical devices. In this paper, the development of low noise voltage reference source is realized by selecting a low noise reference chip, designing relevant peripheral circuits, simulation, electromagnetic shielding, using low temperature drift factor element, low noise power supply and active temperature control. Since existing commercial equipment cannot be used for noise analysis in the 0.1 mHz～1 Hz band, we use a high-precision digital multimeter to test and collect the output voltage of the voltage referencesource under different environmental conditions, including free operation, external shielding shell, external temperature control and shielding temperature control, and use fast Fourier transform method and logarithmic power spectral density method to calculate and process the collected data. The voltage noise spectral density of the developed voltage reference in the 0.01 mHz～1 Hz band is obtained. The experimental results show that the spectrum density reaches 1.85×10-3 V/Hz1/2 at 0.01 mHz, and less than 4.89×10-4 V/Hz1/2 in the frequency range of 0.1 mHz～1 Hz. The development of this low noise voltage reference source and its noise evaluation provide a key device support in terms of laser intensity noise suppression in space gravitational wave detection.

Free time-of-flight expansion of ultracold atoms is an important method to obtain the information of atomic cloud in the momentum space. Magnetic Feshbach resonance manipulates the interaction between atoms, therefore it requires free time-of-flight expansion under high bias magnetic field to obtain the information of interaction energy. Therefore, the spatial distribution of magnetic field has an important influence on the free time-of-flight expansion of atoms.In this paper, we construct two kinds of magnetic coils, and calculate the magnetic field distribution under Helmholtz configuration and study the free time-of-flight expansion of sodium atoms Bose-Einstein condensate. The magnetic field coil parameters affecting the shape and size of atomic cloud after the free time-of-flight expansion are analyzed and discussed. This work provides an important suggestion for designing magnetic Feshbach resonance coils in the future.

The propagation of optical pulses in lossless single-mode fibers can be described by the nonlinear Schrdinger (NLS) equation. When the birefringence effect exists and two or more wave packets with different carrier frequencies appear in the system at the same time, the interaction between them is described by the coupled nonlinear Schrdinger (CNLS) equation. CNLS equation is one of the basic models to describe nonlinear phenomena. In nonlinear optics, in order to realize the wavelength division multiplexing, multiple light field must transmit at the same time. Therefore, CNLS is often used to describe the nonlinear phenomenon of optical soliton in WDM system, birefringence fiber, multimode optical fiber, optical fiber array and Bose-Einstein condensates. In particular, the simultaneous transmission of two ultrashort pulses in the fiber can be described by the CNLS equation with higher order terms. Based on the generalized coupled nonlinear Schrdinger equation, and its N-soliton solution, the effects of self-steepening effect and self-frequency shift effect on the propagation characteristics of N-soliton solution are numerically investigated by using the split-step Fourier method. The results show that both the self-steepening effect and the self-frequency shift effect cause the 1-soliton solution to shift during transmission. For the bound soliton form of 2-soliton solution and 3-soliton solution, self-steepening effect and self-frequency shift effect causesoliton shift and energy redistribution. For 2-soliton solution and 3-soliton solution with breathing-like structure, self-steepness effect and self-frequency shift effect destroy the breathing structure, making the solution split into several solitons with different amplitudes and transmission speeds.

In optical fibers, the nonlinear Schrdinger equation is a theoretical model for studying Akhmediev breather dynamics. Due to the material and characteristics of the fiber itself, including the variable-coefficients into the nonlinear Schrdinger equation is an effective method to reflect the non-uniform effects of nonlinear pulses. Based on the exact solution of the variable-coefficients Hirota equation, it studies the generation and transmission characteristics of the high-power pulse train in dispersion exponentially decreasing fiber in this paper. When the second-order dispersion takes the exponential form, breather can evolve into high- power pulse train with the increase of transmission distance that can propagate stably and the position zc of the stable high-power pulse train is closely related with the modulation intensity β0 and the attenuation index δ of the dispersion coefficient. The results show that the position zc of the stable high-power pulse train increases with the increase of parameter β0 and decreases with the increase of parameter δ. Therefore, the stable high-power pulse train can be formed at any position by adjusting the parameters β0 and a. In addition, the effect of the third-order dispersion on the high-power pulse train is discussed. It shows that the appropriate form of third-order dispersion does not affect the formation of high-power pulse train, while it affects the deviation degree and direction of the high-power pulse train. Finally, in the presence of gain or loss, the amplitude variations of the high-power pulse train during the propagation are studied. The results show that it can control the high-power pulse train by adjusting the parameters providing theoretical guidance for the application of optical communications in practice.

In recent years, terahertz technology has received more and more attention and has made great progress. With the development of terahertz technology and metamaterial, adjustable metamaterial absorbers applied to the terahertz band have good application prospects. Vanadium dioxide (VO2) is a typical reversible phase change material. It is insulative at room temperature and changes to be metallic when the temperature reaches 68 °C. Based on theunique properties of vanadium dioxide (VO2) in terms of phase change, a multi-layer metamaterial absorber with switchable absorption properties is proposed. The absorber is constituted by six layers, from the top layer to the bottom layer are vanadium dioxide (VO2) square ring, polyimide (PI) dielectric layer, vanadium dioxide (VO2) film layer, cross-shaped gold layer, polyimide(PI) dielectric layer, and gold film layer. When vanadium dioxide (VO2) is at the metallic state, the structure can be used as a broadband absorber. The simulation results show that the absorptance exceeds 90% between 2.3 THz and 5.3 THz, which is not sensitive to the polarization of the incident light, and the change of the incident angle has littleeffect on the absorption performance. When vanadium dioxide (VO2) is at insulating state, the structure can be used as a narrow-band absorber. The simulation results show that the absorptance exceeds 99% at 7.1 THz, achieving a perfect absorption effect, which is not sensitive to the polarization of the incident light as well. Therefore, by switching the different states of vanadium dioxide (VO2), the switching of the different absorption properties of the metamaterial absorber is realized. Moreover, it is explored that the structure has good sensing performance when vanadium dioxide (VO2) is in an insulating state and the sensing sensitivity of the structure is 200 GHz/RIU. The absorber has the advantages of switchable absorptionperformance between narrowband and broadband, and multifunctional application. The structure can play an important role in terahertz imaging, detection, communication and sensing, and other emerging terahertz fields.

Terahertz technology has been applied extensively in the fields of imaging, sensing, and detection etc. Various terahertz functional devices based on artificial metamaterials, such as absorbers, filters, and polarization converters, have attracted much attention from researchers. By introducing various tunable elements in the design, such as graphene, photosensitive silicon and vanadium dioxide (VO2), a controllable metamaterial absorber has become a hotspot. The temperature-controlled phase transition of VO2 has great potential in the development of simple and controllable metamaterial absorbers. In this paper, using the phase transition properties of VO2, we propose a dynamically temperature-tunable dual-band ultra-thin terahertz metamaterial absorber, which is composed of gold-VO2 resonator on top layer, SiO2 dielectric spacer and continuous gold film on bottom layer. At room temperature, the phase-change material VO2 is in insulating state, and the proposed absorber achieves dual-band absorption with absorption rates of 94.3% and 99.6% at the resonance frequencies of 4.11 THz and 6.01 THz, respectively; as the temperature rises to 340 K, VO2 is in metallic state, and the two absorption peaks of the absorber are red-shifted achieving absorption rates of 95.8% and 93.4% at the new resonance frequencies of 2.55 THz and 5.29 THz respectively. The thickness of the absorber is only 1/19 and 1/45 of the minimum and maximum operating wavelengths, showing ultra-thin characteristics. Furthermore, the dynamically adjustable absorption mechanism is demonstrated by studying the surface current distributions at resonance frequencies for VO2 in different phase transition. In addition, as the proposed absorber has a centrosymmetric structure whether VO2 is in an insulating or a metallic state, it possesses the characteristics of polarization insensitivity for both TE and TM waves; meanwhile, it also shows good absorption for both TE and TM waves under wide-angle oblique incidence. The tunable dual-band ultra-thin absorber presented here is simple and easy to be fabricated, and has important application prospects in the fields of stealth and detection etc.

The entropy uncertainty relation principle is one of the most fundamental characteristics of quantum information and quantum technology. In this paper, based on the quantum memory-assisted entropy uncertainty relation (QMA-EUR), we study the dynamics of entropy uncertainty for the Heisenberg model of two qubits. A detailed analysis is presented for the effects of Dzyaloshinskii-Moriya (DM) interaction strength D, coupling strength J and temperature T on theentropy uncertainty in both the ferromagnetic (J0) regimes. The numerical result shows that the entropy uncertainty can be reduced by the increase of the interaction strength D or coupling strength J, implying that the measuring outcomes can be predicted more precisely. It is demonstrated that the entropy uncertainty is closely related to the increase of the thermodynamic temperature. It implies that the accuracy of measurement result decreases with the increase of the thermodynamic temperature. Moreover, the effect of DM on the entropy uncertainty of the system in both the ferromagnetic and antiferromagnetic regimes at high temperature or low temperature are discussed respectively. On the one hand, the entropy uncertainty does not approach a constant value in ferromagnetic systems at low temperatures. Besides, in antiferromagnetic systems, the entropy uncertainty is always close to zero at low temperatures, implying that the measuring outcomes can be predicted precisely. As a comparison, in antiferromagnetic systems, the entropy uncertainty is not always close to zero at low temperature. When DM interaction strength D is small, the increase of temperature can improve the entropy uncertainty relation of the system and plays a more significant role in ferromagnetic system. The effective regulation mechanism of the entropy uncertainty of the Heisenberg model is revealed. Moreover, the underlying physics for the dynamical evolution of entropy uncertainty are analyzed by mixedness, where the increase of mixedness is considered to result in the enhancement of uncertainty, and vice versa.

Magnetic sensing based on the color center of nitrogen vacancy in diamond has been considered by scientists as a promising candidate for high sensitivity and integrated solid-state quantum sensors. In this paper,a displacement vibration detection method based on electron spin resonance effect is proposed, which takes the diamond nitrogen vacancy color center as the sensitive unit and uses its high sensitivity mechanism to the magnetic field intensity. We designed and built a vibration generator and a magnetic field detection system. The system consists of a fluorescence focusing system, a current carrying magnetic coil and a ruler. Here, we design an optimal parameter coil under the experimental conditions, change the inner diameter, outer diameter, height and current of the coil respectively, and use the control variable method to determine the final parameters. The fluorescence focusing system is responsible for efficiently exciting and collecting fluorescenceand determining the Zeeman splitting degree of electron spin effect. The current carrying coil is responsible for generating a high linear gradient magnetic field, and the scale is employed as the vibration source to generate vibration signals, so as to drive the current carrying coil to vibrate. In this way, the distance between the coil and the diamond is modulated, and the fluorescence intensity changes accordingly. Then, through rigorous static and dynamic experimental analysis, when the magnetic coil carries a current of 0.1 A, the displacement sensitivity is 25.11 nmHz12, and the theoretical displacement sensitivity is about 2.106 nmHz12, the minimum magnetic sensitivity limit is 0.198 nTHz12, the frequency of the vibration signal is 6.31 Hz, and the amplitude is 0.744 mm. The experiment verifies the feasibility of displacement vibration detection method. It provides a new way for high-precisiondisplacement and vibration detection methods.

Optical resolution photoacoustic microscopy (OR-PAM), benefiting from rich optical contrast, scalable acoustic resolution, and deep penetration depth, is a rapidly developing biomedical imaging technology in recent years. To meet the need of shallow cells imaging in large-scale living organisms, an OR-PAM system with subcellular level imaging resolution and more than one millimeter imaging depth was designed and constructed in this paper. In the OR-PAM system, a homemade single longitudinal mode (SLM) nanosecond (ns) 532 nm pulse laser was adopted as excitation source, and an ultrasonic sensor with a center frequency of 50 MHz was adopted as the acoustic detector, noting that the excitation laser and the ultrasonic detector were coaxially mounted with a common focus. Two-dimensional (2D) and three-dimensional (3D) images was obtained based on a homemade program-controlled 2D electric translation table, as well as an automatic signal acquisition and image reconstruction program. In a single point photoacoustic detection experiment using a agar block embedded with black tape as sample, the signal-to-noise ratio (SNR) of our OR-PAM was 1.35 times higher than that of a conventional OR-PAM system excited by a multi-longitudinal mode pulsed laser, owing to the low amplitude noise, less clutter and good beam quality of the self-made SLM 532 nm excitation laser. On this basis, the key performance index of the OR-PAM system was measured. The imaging depth of the system was determined by a series of single point photoacoustic detection with different excitation laser focus position, while the absorbers were 10 hairs placed at different depths in an imitation sample. Since the measured imaging depth was 1.54 mm, the axial and lateral resolutions of the OR-PAM system was determined using two samples embedded with a human hair and a sharp knife edge at the depth of 1.54 mm, respectively. The measured photoacoustic signal of the human hair was copied and translated in time domain, and when the translated signal and the original signal was added, there existed two maximum peaks in the added signal. Then the axial resolution of the system can be determined using the minimum moving distance corresponding to the translation time that made the two peaks distinguishable, which was 18 m in our experiment. The lateral resolution of the system was tested by scanning along the direction perpendicular to the edge of the sharp knife, which was 8 m in our experiment. It was concluded that the ratio of the imaging depth to the lateral spatial resolution of our OR-PAM system was as high as 192.5. The developed OR-PAM system was also used to reconstruct the 2D images of an imitation samples embedded with carbon fiberfilament and the ear of a living mouse, respectively. High-resolution images were obtained verifying the usability and performance of the OR-PAM system.

With the reduction of the scales in life system for human observation, many novel quantum phenomena have been gradually discovered and studied. However, the dynamic process of quantum phenomena at the microscopicscale often takes place in the time scale from femtosecond to picosecond, while conventional detection methods cannot achieve an effective observation. Based on the theory of quantum mechanics, single molecule coherent modulation microscopic imaging technology makes it possible to observe the quantum phenomena of microscopic organisms by combining ultrafast optics and microscopy. In this review, we first introduce the basic principle of single molecule coherent modulation microscopy imaging technology, which achieves the control of single molecule quantum coherent state by femtosecond laser pulse, and obtains coherent information around single molecule by modem technology. Then, two applications in biology are introduced respectively: (1) The contrast ofbiological imaging can be improved by two orders of magnitude by reducing the self-fluorescence and background noise of biology; (2) the quantum information around single molecule can be obtained by extracting the coherent visibility V, which provides an effective means for the observation of biological microenvironment. Finally, this paper prospects the early diagnosis of cancer based on single molecule coherent modulation microscopy, which will provide a new way for the early diagnosis and prognosis evaluation of cancer.