Topological phases and non-Hermitian topology in tunable nonreciprocal cyclic three-mode optical systems.

We propose a method for simulating a 1D non-Hermitian Su-Schrieffer-Heeger model with modulated nonreciprocal hopping using a cyclic three-mode optical system. The current system exhibits different localization of topologically nontrivial phases, which can be characterized by the winding number. We find that the eigenenergies of such a system undergo a real-complex transition as the nonreciprocal hopping changes, accompanied by a non-Bloch parity-time symmetry breaking. We explain this phase transition by considering the evolution of saddle points on the complex energy plan and the ratio of complex eigenenergies. Additionally, we demonstrate that the skin states resulting from the non-Hermitian skin effect possess higher-order exceptional points under the critical point of the non-Bloch parity-time phase transition. Furthermore, we investigate the non-Hermitian skin phase transition by the directional mean inverse participation ratio and the generalized Brillouin zone. This work provides an alternative way to investigate the novel topological and non-Hermitian effects in nonreciprocal optical systems.

Nonreciprocal P T-symmetric magnon laser in spinning cavity optomagnonics.

We propose a scheme to achieve nonreciprocal parity-time (P T)-symmetric magnon laser in a P T-symmetric cavity optomagnonical system. The system consists of active and passive optical spinning resonators. We demonstrate that the Fizeau light-dragging effect induced by the spinning of a resonator results in significant variations in magnon gain and stimulated emitted magnon numbers for different driving directions. We find that utilizing the Fizeau light-dragging effect allows the system to operate at ultra-low thresholds even without reaching gain-loss balance. A one-way magnon laser can also be realized across a range of parameters. High tunability of the magnon laser is achieved by changing the spinning speed of the resonators and driving direction. Our work provides a new way to explore various nonreciprocal effects in non-Hermitian magnonic systems, which may be applied to manipulate photons and magnons in multi-body non-Hermitian coupled systems.

Conventional photon blockade in the dispersive limit for Tavis-Cummings model.

In the dispersive limit, the conventional photon blockade effect cannot be realized due to the absence of photon nonlinearity. We propose a scheme to recover the photon blockade effect of the dispersive Tavis-Cummings model, which makes it possible to realize the conventional photon blockade effect in the dispersive limit. It is shown that both single-photon and two-photon blockade effects can be recovered at appropriate qubit driving strength. The optimal qubit drive strength and cavity field drive detuning are given analytically. All analyses can be verified by numerical simulation, and the strongest photon blockade effect with the largest average photon number can be produced when the single excitation resonance condition is satisfied. Moreover, we find that the achieved two-photon blockade effect is relatively robust to thermal noise. Our proposal is able to obtain single-photon sources with high purity and high brightness and has great potential for applications in quantum communication processing.

Squeezing-induced nonreciprocal photon blockade in an optomechanical microresonator.

We propose a scheme to generate nonreciprocal photon blockade in a stationary whispering gallery microresonator system based on two physical mechanisms. One of the two mechanisms is inspired by recent work [Phys. Rev. Lett.128, 083604 (2022)10.1103/PhysRevLett.128.083604], where the quantum squeezing caused by parametric interaction not only shifts the optical frequency of propagating mode but also enhances its optomechanical coupling, resulting in a nonreciprocal conventional photon blockade phenomenon. On the other hand, we also give another mechanism to generate stronger nonreciprocity of photon correlation according to the destructive quantum interference. Comparing these two strategies, the required nonlinear strength of parametric interaction in the second one is smaller, and the broadband squeezed vacuum field used to eliminate thermalization noise is no longer needed. All analyses and optimal parameter relations are further verified by numerically simulating the quantum master equation. Our proposed scheme opens a new avenue for achieving the nonreciprocal single photon source without stringent requirements, which may have critical applications in quantum communication, quantum information processing, and topological photonics.

Nonreciprocal photon blockade in a spinning optomechanical system with nonreciprocal coupling.

A scheme is presented to achieve quantum nonreciprocity by manipulating the statistical properties of the photons in a composite device consisting of a double-cavity optomechanical system with a spinning resonator and nonreciprocal coupling. It can be found that the photon blockade can emerge when the spinning device is driven from one side but not from the other side with the same driving amplitude. Under the weak driving limit, to achieve the perfect nonreciprocal photon blockade, two sets of optimal nonreciprocal coupling strengths are analytically obtained under different optical detunings based on the destructive quantum interference between different paths, which are in good agreement with the results obtained from numerical simulations. Moreover, the photon blockade exhibits thoroughly different behaviors as the nonreciprocal coupling is altered, and the perfect nonreciprocal photon blockade can be achieved even with weak nonlinear and linear couplings, which breaks the orthodox perception.

Parametrically amplified nonreciprocal magnon laser in a hybrid cavity optomagnonical system.

We propose a scheme to achieve a tunable nonreciprocal magnon laser with parametric amplification in a hybrid cavity optomagnonical system, which consists a yttrium iron garnet (YIG) sphere and a spinning resonator. We demonstrate the control of magnon laser can be enhanced via parametric amplification, which make easier and more convenient to control the magnon laser. Moreover, we analyze and evaluate the effects of pump light input direction and amplification amplitude on the magnon gain and laser threshold power. The results indicate that we can obtian a higher magnon gain and a broader range of threshold power of the magnon laser. In our scheme both the nonreciprocity and magnon gain of the magnon laser can be increased significantly. Our proposal provides a way to obtain a novel nonreciprocal magnon laser and offers new possibilities for both nonreciprocal optics and spin-electronics applications.

Research on Temperature Compensation of Multi-Channel Pressure Scanner Based on an Improved Cuckoo Search Optimizing a BP Neural Network.

A multi-channel pressure scanner is an essential tool for measuring and acquiring various pressure parameters in aerospace applications. It is important to note, however, that the pressure sensor of each of these channels will drift significantly with the increase in the temperature range of the pressure measurement, and the output voltage of each of these channels will show nonlinear characteristics, which will constrain the improvements in the accuracy of the measurement. In the regression fitting process, it is difficult to fit nonlinear data with the traditional least-squares method, which leaves pressure measurement accuracy unsatisfactory. A temperature compensation method based on an improved cuckoo search optimizing a BP neural network for a multi-channel pressure scanner is proposed in this paper to improve pressure measurement accuracy in a wide temperature range. Using the chaotic simplex algorithm, we first improved the cuckoo search algorithm, then optimized the connection weights and thresholds of the BP neural network, and finally constructed an experimental calibration system to investigate the temperature compensation of the multi-channel pressure scanning valves in the -40 °C to 60 °C temperature range. The compensation test results show that the algorithm has a better compensation effect and is more suitable for the temperature compensation of multi-channel pressure scanners than the traditional least-squares method and the standard RBF and BP neural networks. The maximum full-scale error of all 32 channels is 0.02% FS (full-scale error) and below, which realizes its high-accuracy multi-point pressure measurement in a wide temperature range.

Quantum entanglement and one-way steering in a cavity magnomechanical system via a squeezed vacuum field.

We propose a simple scheme to generate quantum entanglement and one-way steering between distinct mode pairs in a generic cavity magnomechanical system, which is composed of a microwave cavity and a yttrium iron garnet sphere supporting magnon and phonon modes. The microwave cavity is pumped by a weak squeezed vacuum field, which plays an important role for establishing quantum entanglement and steering. It is found that when the magnon mode is driven by the red-detuned laser, the maximum entanglement between cavity mode and phonon mode and the maximum phonon-to-photon one-way steering can be effectively generated via adjusting the ratio of two coupling rates. While under the much weaker magnomechanical coupling, the quantum entanglement and one-way steering between cavity mode and magnon mode can be achieved, where the steering direction is determined merely by the relative dissipation strength of the cavity to the magnon mode. More interestingly, we reveal that the robustness to the temperature for entanglement and steering between any mode pairs can be evidently enhanced by selecting the squeezing parameter appropriately.

Design and evaluation of cooling workwear for miners in hot underground mines using PCMs with different temperatures.

Cooling workwear using phase change materials (PCMs) was designed for miners in hot underground mines. A new arrangement of PCM packs was introduced that used 15 °C PCMs as the inner layer and 23 °C PCMs as the outer layer (15&23). Its performance was investigated using thermal manikin and human subject tests by comparison with clothing without PCMs (CON), with 15 °C PCMs (15&15) and with melted PCMs (mPCM) in a climate chamber (30 °C, 80% relative humidity). The PCM cooling workwear significantly increased the manikin heat loss, attenuated the rise of skin temperatures and improved thermal sensation and comfort. The cooling duration was extended in 15&23 as compared with 15&15. The added PCMs did not affect the perceptual exertion and body mobility. In summary, cooling workwear using PCMs with different temperatures can be an effective option for miners' personal cooling in a hot and humid environment.

Observing two-particle Anderson localization in linear disordered photonic lattices.

We theoretically and systematically investigate Anderson localization of two bosons with nearest-neighbor interaction in one dimension under short- and long-time scales, two types of disorders, and three types of initial states, which can be directly observed in linear disordered photonic lattices via two experimentally measurable physical quantities, participation ratio and spatial correlation. We find that the behavior of localization characterized by the participation ratio depends on the strength of interaction and the type of disorder and initial condition. Two-boson spatial correlation reveals more novel and unique features. In the ordered case, two types of two-boson bindings and bosonic "fermionization" are shown, which are intimately attributed to the band structure of the system. In the disordered case, the impact of interaction on the two-boson Anderson localization is reexamined and the joint effect of disorder and interaction is addressed. We further demonstrate that the independence of the participation ratio or spatial correlation on the sign of interaction can be eliminated by employing an initial state that breaks one of two specific symmetries. Finally, we elucidate the relevant details of the experimental implementation in a two-dimensional linear photonic lattice.

Risk assessment of freezing injury during overwintering of wheat in the northern boundary of the Winter Wheat Region in China.

Freezing injury is one of the main restriction factors for winter wheat production, especially in the northern part of the Winter Wheat Region in China. It is very important to assess the risk of winter wheat-freezing injury. However, most of the existing climate models are complex and cannot be widely used. In this study, Zunhua which is located in the northern boundary of Winter Wheat Region in China is selected as research region, based on the winter meteorological data of Zunhua from 1956 to 2016, seven freezing disaster-causing factors related to freezing injury were extracted to formulated the freezing injury index (FII) of wheat. Referring to the historical wheat-freezing injury in Zunhua and combining with the cold resistance identification data of the National Winter Wheat Variety Regional Test (NWWVRT), consistency between the FII and the actual freezing injury situation was tested. Furthermore, the occurrence law of freezing injury in Zunhua during the past 60 years was analyzed by Morlet wavelet analyze, and the risk of freezing injury in the short term was evaluated. Results showed that the FII can reflect the occurrence of winter wheat-freezing injury in Zunhua to a certain extent and had a significant linear correlation with the dead tiller rate of wheat (P = 0.014). The interannual variation of the FII in Zunhua also showed a significant downward trend (R2 = 0.7412). There are two cycles of freezing injury in 60 years, and it showed that there's still exist a high risk in the short term. This study provides reference information for the rational use of meteorological data for winter wheat-freezing injury risk assessment.

Preparation and characterization of phytosterol-loaded nanoparticles with sodium caseinate/dextran conjugates.

Sodium caseinate (SC)/dextran conjugates were prepared via Maillard reaction under controlled dry-heating conditions. Moreover, the nanoparticles of phytosterols (PS) encapsulated by SC or SC/dextran were produced using the emulsion evaporation method. The encapsulation efficiency (78.81 ± 5.22%) of PS in SC/dextran nanoparticles was higher than that (73.5 ± 2.78%) in SC nanoparticles. Compared with the compact and dense structure of SC nanoparticles, SC/dextran nanoparticles existed as relatively loose aggregates. The result of differential scanning calorimetry demonstrated that the encapsulation of PS greatly decreased its crystallinity. The released rates of PS from SC and SC/dextran nanoparticles under acidic gastric conditions were 8.59% and 4.73%, respectively. After 7 h of intestinal digestion, the released rate (52.19%) of PS from SC/dextran nanoparticles was significantly higher than that from SC (32.67%) nanoparticles. Therefore, SC/dextran conjugates prepared by the Maillard reaction are more suitable to be used as wall material for the nano-encapsulation of PS.

Generation and transfer of squeezed states in a cavity magnomechanical system by two-tone microwave fields.

We propose a scheme to generate squeezed states of magnon and phonon modes and verify squeezing transfer between different modes of distinct frequencies in a cavity magnomechanical system which is composed of a microwave cavity and a yttrium iron garnet sphere. We present that by activating the magnetostrictive force in the ferrimagnet, realized by driving the magnon mode with red-detuned and blue-detuned microwave fields, the driven magnon mode can be prepared in a squeezed state. Moreover, the squeezing can be transferred to the cavity mode via the cavity-magnon beamsplitter interaction with strong magnomechanical coupling. We show that under the weak coupling regime, large mechanical squeezing of phonon mode can be achieved, which verifies that our scheme can find the existence of quantum effects at macroscopic scales. Furthermore, distinct parameter regimes for obtaining large squeezing of the magnons and phonons are given, which is the principal feature of our scheme. The considered scheme can be extended to hybrid optical systems, and can facilitate the advancement for realization of strong mechanical squeezing in cavity magnomechanical systems.

Localized photonic states and dynamic process in nonreciprocal coupled Su-Schrieffer-Heeger chain.

We investigate the localized photonic states and dynamic process in one-dimensional nonreciprocal coupled Su-Schrieffer-Heeger chain. Through numerical calculation of energy eigenvalue spectrum and state distributions of the system, we find that different localized photonic states with special energy eigenvalues can be induced by the nonreciprocal coupling, such as zero-energy edge states, interface states and bound states with pure imaginary energy eigenvalues. Moreover, we analyze the dynamic process of photonic states in such non-Hermitian system. Interestingly, it is shown that the nonreciprocal coupling has an evident gathering effect on the photons, which also break the trapping effect of topologically protected edge states. In addition, we consider the impacts of on-site defect potentials on the dynamic process of photonic states for the system. It is indicated that the photons go around the defect lattice site and still present the gathering effect, and different forms of laser pulses can be induced with the on-site defect potentials in different lattice sites. Furthermore, we present the method for the quantum simulation of current model based on the circuit quantum electrodynamic lattice.

Dissipative bosonic squeezing via frequency modulation and its application in optomechanics.

The dissipative squeezing mechanism is an effective method to generate the strong squeezing, which is important in the precision metrology. Here, we propose a practical method to achieve arbitrary bosonic squeezing via introducing frequency modulation into the coupled harmonic resonator model. We analyze the effect of frequency modulation and give the analytical and numerical squeezing results, respectively. To measure the accurate dynamic squeezing in our proposal, we give a more general defination of the relative squeezing degree. Finally, the proposed method is extended to generate the strong mechanical squeezing (>3 dB) in a practical optomechanical system consisting of a graphene mechanical oscillator coupled to a superconducting microwave cavity. The result indicates that the strong mechanical squeezing can be effectively achieved even when the mechanical oscillator is not initially in its ground state. The proposed method expands the study on nonclassical state and does not need the bichromatic microwave driving technology.

Quantum walks in periodically kicked circuit QED lattice.

We investigate the quantum walks of a single particle in a one-dimensional periodically kicked circuit quantum electrodynamics lattice. It is found that the dynamic process of the quantum walker is affected by the strength of incommensurate potentials and the driven periods of the system. We calculate the mean square displacement to illustrate the dynamic properties of the quantum walks, which shows that the localized process of the quantum walker presents the zero power-law index distribution. By calculating the mean information entropy, we find that the next-nearest-neighbor interactions have a remarkable deviation effects on the quantum walks and make a more stricter parameter condition for the localization of the quantum walker. Moreover, assisted by the lattice-based cavity input-output process, the localized features of circuit quantum electrodynamics lattice can be observed by measuring the average photon number of the cavity field in the steady state.

Enhanced photon blockade in an optomechanical system with parametric amplification.

We propose a scheme to enhance the single- and two-photon blockade effects significantly in a nonlinear hybrid optomechanical system with optical parametric amplification (OPA). The scheme does not rely on strong single-photon optomechanical coupling and can eliminate the disadvantages of suppressing multi-photon excitation incompletely. Through analyzing the single-photon blockade (1PB) mechanism and optimizing the system parameters, we obtain a perfect 1PB with a high occupancy probability of single-photon excitation, which means that a high-quality and efficient single-photon source can be generated. Moreover, we find that not only the two-photon blockade (2PB) effect is significantly enhanced, but also the region where 2PB occurs is widened when OPA exists, where we also derive the optimal parameter condition to maximize two-photon emission and higher photon excitations intensely suppressed at the same time.

Controllable photonic and phononic topological state transfers in a small optomechanical lattice.

We propose a scheme to achieve the photonic and the phononic state transfers via the topological protected edge channel based on a one-dimensional small optomechanical lattice. We find that the optomechanical lattice can be mapped into a Su-Schrieffer-Heeger model after eliminating the counter rotating wave terms. By dint of the edge channel of the Su-Schrieffer-Heeger model, we show that the quantum state transfer between the photonic left and the right edge states can be achieved with a high fidelity. Especially, our scheme can also achieve another phononic state transfer based on the same channel via controlling the next-nearest-neighboring interactions between the cavity fields; this is different from the previous investigations achieving only one kind of quantum state transfer. Our scheme provides a novel, to the best of our knowledge, path to switch two different kinds of quantum state transfers in a controllable way.