Nonlinear Quantum Optical Springs and Their Nonclassical Properties

The original idea of quantum optical spring arises from the requirement of quantization of the frequency of oscillations in the Hamiltonian of harmonic oscillator. This purpose is achieved by considering a spring whose constant （and so its frequency） depends on the quantum states ofanother system. Recently, it is realized that by the assumption of frequency modulation of ω to ω √1＋ μα＋α the mentioned idea can be established. In the present paper, we generalize the approach of quantum optical spring with particular attention to the dependence or trequency to the intensity of radiation field that naturally observes in the nonlinear coherent states, from which we arrive at a physical system has been called by us as nonlinear quantum optical spring. Then, after the introduction of the generalized tlamiltonian of nonlinear quantum optical spring and it＇s solution, we will investigate the nonclassical properties of the obtained states. Specially, typical collapse and revival in the distribution functions and squeezing parameters, as particular quantum features, will be revealed.

Quantum optical ABCD theorem in two-mode case

By introducing the entangled Fresnel operator （EFO） this paper demonstrates that there exists ABCD theorem for two-mode entangled case in quantum optics. The canonical operator method as mapping of ray-transfer ABCD matrix is explicitly shown by EFO＇s normally ordered expansion through the coherent state representation and the technique of integration within an ordered product of operators.

Quantum optical correlation through metamaterials

Based on the quantization scheme of the radiation fields in the dispersive and absorptive magnetic media, the normally ordered correlation functions of the outgoing field through a metamaterial plate are obtained. Then the relative photon-number densities of the transmitted field, the reflected field and the absorbed field are gotten through the correlation functions. Furthermore, the contributions of the relative permittivity and permeability of the metamaterials to the transmission are analyzed. Our results show that the permittivity and permeability reinforce the transmission for frequencies that are big compared with the magnetic resonance frequency.

Multiformity of Optical Quantum Coherence Systems with Y and Inverted Y-type Schemes

Y and inverted Y-type four-level schemes for optical quantum coherence systems,which may be intuitivelyconsidered to be very simple,have not been studied intensively till now.In this paper,we present the multiformity ofthese two types of schemes by considering that they can be classified into nine possible level styles as the second-ordersub-schemes using laser fields.Further we point out the complexity of their more than one hundred realistic configurationsas the third-order four-level sub-schemes that may appear in the optical quantum coherence experiments.Throughoutthis paper we review which configurations have been studied in some research aspects and which ones not,accordingto our knowledge,in order to be propitious to next steps of theoretical and experimental investigations,especially forapplications in the fields of quantum optics,quantum information science,laser spectroscopy,and so on.

Quantum optical devices based on four-wave mixing in hot rubidium vapor

In this paper,we briefly review the recent experimental progresses in quantum optics based on four-wave mixing(FWM) processes in hot rubidium vapor,particularly our two recent experiments in quantum information.We have experimentally produced strong quantum correlations between three bright beams generated by two cascaded FWM processes.The intensity difference squeezing with the cascaded system is enhanced to(-7.0±0.1)d B from the(-5.5±0.1)d B/(4.5±0.1)d B with only one FWM process.Also,this system can be easily extended to multiple modes using multiple FWM processes.Besides,we have also successfully realized a cascade all-optical transistor(AOT),which is driven by a very weak light beam about 800 photons in total.The required probe power for achieving a switching efficiency of 50% can be as low as 180 p W,and it can manipulate a light beam with power of 5.0×106 times more,which proves the cascade of the AOT.Both experiments may find wide applications in quantum information and optical communication.

Intersubband optical absorption of electrons in double parabolic quantum wells of Al_xGa_(1-x)As/Al_yGa_(1-y)As

Some realizable structures of double parabolic quantum wells（DPQWs） consisting of Al_xGa_（1-x）As/Al_yGa_（1-y）As are constructed to discuss theoretically the optical absorption due to the intersubband transition of electrons for both symmetric and asymmetric cases with three energy levels of conduction bands. The electronic states in these structures are obtained using a finite element difference method. Based on a compact density matrix approach, the optical absorption induced by intersubband transition of electrons at room temperature is discussed. The results reveal that the peak positions and heights of intersubband optical absorption coefficients（IOACs） of DPQWs are sensitive to the barrier thickness, depending on Al component. Furthermore, external electric fields result in the decrease of peak, and play an important role in the blue shifts of absorption spectra due to electrons excited from ground state to the first and second excited states. It is found that the peaks of IOACs are smaller in asymmetric DPQWs than in symmetric ones. The results also indicate that the adjustable extent of incident photon energy for DPQW is larger than for a square one of a similar size. Our results are helpful in experiments and device fabrication.

Tuning of the Electron Spin Relaxation Anisotropy via Optical Gating in GaAs/AlGaAs Quantum Wells

The carrier-density-dependent spin relaxation dynamics for modulation-doped GaAs/Al0.3 Gao,TAs quantum wells is studied using the time-resolved magneto-Kerr rotation measurements. The electron spin relaxation time and its in-plane anisotropy are studied as a function of the optically injected electron density, Moreover, the relative strength of the Rashba and the Dresselhaus spin-rbit coupling fields, and thus the observed spin relaxation time anisotropy, is further tuned by the additional excitation of a 532nm continuous wave laser, demonstrating an effective spin relaxation manipulation via an optical gating method.

Decoherence Effect and Beam Splitters for Production of Quasi-Amplified Entangled Quantum Optical Light

We let a set of beam splitters of vacuum mode with a chosen transmittance parameter η in interaction with a separable coherent states.This model induces the production of an attenuated quantum channels based on entangled optical states.Indeed,the decoherence effect is exploited positively here to generate such kind of quantum channels.Next,the amplitude damping and the entanglement amount of these produced channels are enhanced thereafter by a probabilistic quasi amplification process using again a 50 : 50 beam splitter.

Controlling the Directed Quantum Transport of Ultracold Atoms in an Optical Lattice with a Periodic Driving Field

We propose a new method to control the directed quantum transport of ultracold atoms in a one-dimensional optical lattice. In this proposal, the effective tunneling between the neighboring sites can be adjusted via coherent destruction of tunneling by tuning the phase of the external field, instead of using the driving field intensity or the frequency, thus the directed quantum transport of ultracold atoms can be coherently controlled in a nmch easier manner. Our proposal overcomes the major drawback of the method used by Creffield et al [Phys. Rev. Lett. 99 （2007） 110501], and can be implemented, in principle, in any one-dimensional optical lattice. Some potential applications of the scheme are also discussed.

Low-power system model for quantum entangled photon-pair source

The quantum entangled photon-pair source,as an essential component of optical quantum systems,holds great potential for applications such as quantum teleportation,quan-tum computing,and quantum imaging.The current workhorse technique for preparing photon pairs involves performing spon-taneous parametric down conversion(SPDC)in bulk nonlinear crystals.However,the current power consumption and cost of preparing entangled photon-pair sources are relatively high,pos-ing challenges to their integration and scalability.In this paper,we propose a low-power system model for the quantum entan-gled photon-pair source based on SPDC theory and phase matching technology.This model allows us to analyze the per-formance of each module and the influence of component cha-racteristics on the overall system.In our experimental setup,we utilize a 5 mW laser diode and a typical type-II barium metabo-rate(BBO)crystal to prepare an entangled photon-pair source.The experimental results are in excellent agreement with the model,indicating a significant step towards achieving the goal of low-power and low-cost entangled photon-pair sources.This achievement not only contributes to the practical application of quantum entanglement lighting,but also paves the way for the widespread adoption of optical quantum systems in the future.

First-Principles Calculation on Geometric,Electronic and Optical Properties of Fully Fluorinated Stanene:a Large-Gap Quantum Spin Hall Insulator

The searches for large-gap quantum spin Hall insulators are important for both practical and fundamental inter- ests. In this work, we present a theoretical observation of the two-dimensional fully fluorinated stanene （SnF） by means of density functional theory. Remarkably, a significant spin-orbit coupling is observed for the SnF monolayer in the valence band at the F point, with a considerable indirect band gap of 278 meV. The direct gap of the SnF monolayer is at the F point, which is slightly larger by as much as 381 meV. In addition, the elastic modulus of the SnF monolayer is about 20J/m^2, which is comparable with the in-plane stiffness of black phos- phorus monolayer along the x-direction （~28.94 J/m^2）. Finally, the optical properties of stanene, SnF monolayer and stanene/SnF bilayer are calculated, in which the stanene/SnF bilayer is supposed to be an attractive sunlight absorber.

Photonic implementation of quantum gravity simulator

Detecting gravity-mediated entanglement can provide evidence that the gravitational field obeys quantum mechanics.We report the result of a simulation of the phenomenon using a photonic platform.The simulation tests the idea of probing the quantum nature of a variable by using it to mediate entanglement and yields theoretical and experimental insights,clarifying the operational tools needed for future gravitational experiments.We employ three methods to test the presence of entanglement:the Bell test,entanglement witness,and quantum state tomography.We also simulate the alternative scenario predicted by gravitational collapse models or due to imperfections in the experimental setup and use quantum state tomography to certify the absence of entanglement.The simulation reinforces two main lessons:(1)which path information must be first encoded and subsequently coherently erased from the gravitational field and(2)performing a Bell test leads to stronger conclusions,certifying the existence of gravity-mediated nonlocality.

IN SITU IMAGING OF BREAST CANCER CELLS USING GREEN SEMICONDUCTOR QUANTUM DOTS

The breast cancer is the most common cause of cancer death in women. To establish an early stage in situ imaging of breast cancer cells, green quantum dots （QDs） are used as a fluorescent signal generator. The QDs based imaging of breast cancer cells involves anti-HER2/neu antibody for labeling the over expressed HER2 on the surface of breast cancer cells. The complete assay involves breast cancer cells, biotin labeled antibody and streptavidin conjugated QDs. The breast cancer cells are grown in culture plates and exposed to the biotin labeled antibodies, and then exposed to streptavidin labeled QDs to utilize the strong and stable biotin-streptavidin interaction. Fluorescent images of the complete assay for breast cancer cells are evaluated on a microscope with a UV light source. Results show that the breast cancer cells in the complete assay are used as fluorescent cells with brighter signals compared with those labeled by the organic dye using similar parameters and the same number of cells.

Effects of Turbulent Aberrations on Probability Distribution of Orbital Angular Momentum for Optical Communication

Effects of atmospheric turbulence tilt, defocus, astigmatism and coma aberrations on the orbital angular momentum measurement probability of photons propagating in weak turbulent regime are modeled with Rytov approximation. By considering the resulting wave as a superposition of angular momentum eigenstates, the or- bital angular momentum measurement probabilities of the transmitted digit are presented. Our results show that the effect of turbulent tilt aberration on the orbital angular momentum measurement probabilities of photons is the maximum among these four kinds of aberrations. As the aberration order increases, the effects of turbulence aberrations on the measurement probabilities of orbital angular momentum generally decrease, whereas the effect o[ turbulence defocus can be ignored. For tilt aberration, as the difference between the measured orbital angular momentum and the original orbital angular momentum increases, the orbital angular momentum measurement probability decreases.

A concise review of Rydberg atom based quantum computation and quantum simulation

Quantum information processing based on Rydberg atoms emerged as a promising direction two decades ago.Recent experimental and theoretical progresses have shined exciting light on this avenue.In this concise review,we will briefly introduce the basics of Rydberg atoms and their recent applications in associated areas of neutral atom quantum computation and simulation.We shall also include related discussions on quantum optics with Rydberg atomic ensembles,which are increasingly used to explore quantum computation and quantum simulation with photons.

Three-Dimensional Analytical Formula for Oblique and Off-Axis Gaussian Beams Propagating through a Cat-Eye Optical Lens

Based on the Collins formula in a cylindrical coordinate system and the method of introducing a hard aperture function into a finite sum of complex Gaussian functions, an approximate three-dimensional analytical formula for oblique and off-axis Gaussian beams propagating through a cat-eye optical lens is derived. Numerical results show that a reasonable choice of the obliquity factor would result in a better focus beam with a higher central intensity at the return place than that without obliquity, whereas the previous conclusion based on geometry optics is that the highest central intensity could be obtained when there is no obliquity.

Quantum photonics based on metasurfaces

From metamaterials to metasurfaces,optical nano-structure has been widely investigated for novel and high efficiency functionalities.Apart from the intrisinsic properties of composite material,rich capabilities can be derived from the judi-cious design of metasurfaces,which enable more excellent and highly integrated optical devices than traditional bulk op-tical elements.In the meantime,the abundant manipulation abilites of light in the classical domain can be carried over in-to quantum domain.In this review,we highlight recent development of quantum optics based on metasurfaces,ranging from quantum plasmonics,generation,manipulation and appplication of quantum light to quantum vaccum engineering etc.Finally,some promising avenues for quantum optics with the help of optical metasurface are presented.

Highly Efficient Continuous-Wave Mid-Infrared Intracavity Singly Resonant Optical Parametric Oscillator Based on MgO：PPLN

We present a compact all-solid-state cw mid-infrared intracavity singly resonant optical parametric oscillator （OPO） that is based on a self-fabricated 1-mm-thick 40-mm-long doped MgO periodically poled lithium niobate （MgO：PPLN）. At a diode pump power of 15.6 W, the compact intracavity Nd：YVO4/MgO：PPLN OPO produced 1.9 W output power at 3.19μm, corresponding to conversion efficiency of 12.2% from the laser diode pump to OPO idler output.

Equivalent Method of Solving Quantum Efficiency of Reflection-Mode Exponential Doping GaAs Photocathode

The mathematical expression of the electron diffusion and drift length LDE of exponential doping photocathode is deduced. In the quantum efficiency equation of the reflection-mode uniform doping cathode, substituting LDE for LD, the equivalent quantum efficiency equation of the reflection-mode exponential doping cathode is obtained. By using the equivalent equation, theoretical simulation and experimental analysis shows that the equivalent index formula and formula-doped cathode quantum efficiency results in line. The equivalent equation avoids complicated calculation, thereby simplifies the process of solving the quantum efficiency of exponential doping photocathode.

Strain-Compensated InGaAs/InAlAs Quantum Cascade Detector of 4.5 μm Operating at Room Temperature

We present a strain-compensated InP-based InGaAs/InAlAs photovoltaic quantum cascade detector grown by solid source molecular beam epitaxy. The detector is based on a vertical intersubband transition and electron transfer on a cascade of quantum levels which is designed to provide longitudinal optical phonon extraction stairs. By careful structure design and growth, the whole epilayer has a residual strain toward InP substrate of only -2.8× 10^-4. A clear narrow band detection spectrum centered at 4.5 μm has been observed above room temperature for a device with 200／times 200 ×μm^2 square mesa.