Lossless single-photon shaping via heralding

Using spontaneous optical parametric downconversion, we experimentally demonstrate heralded generation of shaped single photons, whose modes are tailored indirectly by applying amplitude modulation on the pump field that drives the downconversion process. Our experiment opens a door to creating high-quality, mode-shaped single photons at a substantially higher efficiency than is possible with the existing method of direct single-photon shaping.     

联合调制量子密钥分配系统

本文提出了一种对每一个单光子信号进行相位和偏振两种 编码调制的联合调制量子密钥分配(QKD)系统. 结合复合QKD系统的双速协议, 本文给出了在理想情形下可以通过一个信号光子生成两比特密钥的QKD协议, 明显提高了QKD协议的内禀光子利用率. 在稳定性方面, 本文发展了联合调制的Michelson型QKD系统, 从而在原理上解决了联合调制QKD系统的稳定性问题. 关键词： 量子密钥分配 双速协议 联合调制 量子密钥分配系统的稳定性     

可调谐激光二极管吸收光谱系统信号分析及谱线畸变校正技术研究

利用可调谐激光二极管吸收光谱技术进行气体检测时,波长调制伴随的光强幅度调制,会使解调出的谐波谱线发生畸变.在傅里叶分析的基础上对可调谐激光二极管吸收光谱任意调制幅度的波长调制光谱信号进行了分析,给出了光强幅度调制引起吸收谱线畸变的理论解释.提出了在波长调制过程中进行旧步平抑幅度调制的方法来消除谱线畸变,设计了实验方案并...     

受驱动光学系统多光子量子统计理论(Ⅰ)——Fokker-Planck方程和良腔情况

我们应用广义Wigner分布的Fokker-Planck方程的系统方法,研究了受驱动光学系统的多光子跃迁过程。得到多光子过程普遍的Fokker-Planck方程、态方程以及良腔情况下透射光谱公式。计算了n光子双稳态的透射光谱并与单光子情况进行比较。还证明了在良腔情况,对于多光子过程,原子-原子关联也可以忽略。 关键词：     

Single-Photon Momentum Displacement in Resonator Array with Optomechanics

We present the single-photon scattering in a resonator array system with optomechanical by solving the Lippmann-Schwinger equation iteratively. Up to the first order of the radiation pressure interaction, the single-photon transport is formulated as a three-channel scattering process. We calculate the scattering currents in different channels and obtain the transmission spectrum which shows a momentum displacement effect.     

Structural, electronic, vibrational, and elastic properties of SWCNTs doped with B and N: an ab initio study

A microscopic model is developed in order to analyse the effects of dissipations on single-photon transport in a coupled cavity array where one of the cavities is coupled to a three-level atom and both cavities and the three-level atom are coupled to an external environment. By employing the quasi-boson approach, the single-photon transmission and reflection amplitudes are found exactly for the Ξ-type, V-type and Λ-type three-level atoms. We focus on the dissipation properties in the case of the Λ-type system. Comparing the dissipative case with the nodissipative one, it can be found that the dissipations of the cavities and the Λ-type three-level atom significantly affect the transmission amplitude of single-photon transport. Whether the atom is in tune with the resonant frequency of the cavity or not, incomplete reflection is mostly caused by atom dissipation near the middle dip of the single-photon transport spectrum, while reduced transmission appears to be mainly controlled by cavity dissipation. Dissipations broaden the line width of the single photon transport spectrum.     

Theoretical analysis and experimental research on non-cavitation noise modulation mechanism of underwater counter-rotation propeller

The underwater counter-rotation propeller non-cavitation noise has an obvious modulation characteristic which is due to the interaction of flow and blade. A modulation mechanism is presented in this paper. A sound pressure spectrum model is presented to describe its non-cavitation noise with application of generalized acoustic analogy method, the modulation mechanism is expressed with the improvement of sound pressure model. The power spectrum and modulation spectrum are presented by numerical simulation. Theoretical analysis and numerical simulation results are verified by the cavitation tunnel experiment. The modulation model of counter-rotation propeller is beneficial to the prediction modulation characteristics and identification of underwater high-speed vehicles.     

Electro-optic modulation of single photons

We use the Stokes photon of a biphoton pair to set the time origin for electro-optic modulation of the wave function of the anti-Stokes photon thereby allowing arbitrary phase and amplitude modulation. We demonstrate conditional single-photon wave functions composed of several pulses, or instead, having Gaussian or exponential shapes.     

水下对转桨无空化噪声调制理论分析与试验研究

水下对转桨无空化噪声由流场-桨叶相互作用引起,调制特性是水下对转桨无空化噪声的重要特征,本文研究了水下对转桨无空化辐射噪声调制机理。首先利用广义声类比方法得到了无空化条件下水下对转桨的远场声压谱,建立了水下对转桨无空化噪声的调制模型,然后数值仿真了模型对转桨无空化噪声的功率谱和调制谱,最后在空泡水筒中进行了模型对转桨的无空化噪声测量试验,数值仿真结果和试验验证了调制模型的准确性。该模型对于水下对转桨无空化噪声调制特性预报及目标识别具有重要价值.      

The Decoy-State Measurement-Device-Independent Quantum Key Distribution with Heralded Single-Photon Source

Based on heralded single-photon source (HSPS), a decoy-state measurement-device-independent quantum key distribution (MDI-QKD) protocol is proposed in this paper. The MDI-QKD protocol mainly uses orbital angular momentum (OAM) states and pulse position modulation (PPM) technology to realize the coding of the signal states in heralded single-photon source. The three-intensity decoy states are used to avoid the attacks against the light source. Moreover, the formula of key generation rate is given by computing the lower bound of the yield of single-photon pairs and the upper bound of the error rate of single-photon pairs. Numerical simulation shows that the new MDI-QKD protocol has high key generation rate and low error rate. Moreover, the secure communication distance can be up to 450 km.

     

差分浓度调制激光光谱技术

报道了在近红外波段的差分浓度调制激光光谱技术的研究工作,以N2^ 的浓度调制光谱为例,研究了浓度调制制激光光谱技术的特性。将浓度调制光谱与速度调制光谱相结合得到了速度调制光谱调制度与各因素的关系。同时展示的Ar激光发态的差分浓度调制光谱表明,差分浓度调制光谱技术在探测中性自由基分子和分子离子方面具有很大的应用潜力。     

基于拉盖尔-高斯光束的单光子捕获概率研究

单光子源通常采用基于高斯光束的高度衰减激光脉冲,假设激光束具有初始高斯时域脉冲波形和TEM01模拉盖尔-高斯空域分布.基于折射率起伏的Rytov近似和修正von Karman谱模型,研究了大气湍流对星地量子通信单光子捕获概率的影响;建立了上行信道和下行信道的单光子捕获概率理论模型;针对低轨卫星-地面站间激光链路,对单光子捕获概率进行了分析.结果表明:上行信道的单光子捕获概率强烈依赖于地面折射率结构常数C2n(0),且随着C2n(0)的增加而减小;然而,下行信道的单光子捕获概率并不依赖于C2n(0),即大气湍流对其没有影响.     

双强度调制偏振光谱测量原理及仿真

针对单强度调制偏振光谱测量技术存在混叠且有效光程差有限的缺点,提出双强度调制偏振光谱测量新方法,该方法通过双强度调制干涉信号的和差处理,即保证单强度调制偏振光谱测量的优点,又能有效消除混叠现象,提高有效光程差和光谱分辨率,再对和差处理后的干涉信号进行傅里叶变换即可得到被测偏振光谱。文章对双强度调制偏振光谱测量方法进行了理论推导,并通过MATLAB对模拟入射光偏振光谱的干涉信号和傅里叶反演光谱进行仿真;仿真结果显示,该方法和差处理后可有效消除混叠且有效光程差提高一倍。通过理论分析和仿真验证了该方法的可行性,为进一步的工程实现提供理论支撑。     

光纤Sagnac干涉仪中单光子干涉及路由控制

介绍一种光纤中稳定的单光子干涉以及单光子路由控制方式. 使用Sagnac单光子环形干涉仪，通过分时相位调制，改变其顺时针和逆时针两路光子间的相位差. 在Sagnac单光子环形干涉仪中，顺时针和逆时针两路光子走过的是同一段光纤，简便有效地补偿了光纤长度随时间缓变带来的相位涨落，而且两路光子经历了相同的偏振模色散，较好地抑制了偏振态波动对单光子干涉的影响. 在长达5km的1550nm单模光纤中，获得大于98%的单光子干涉和大于90%单光子路由控制；在长度为27和50km光纤环路中，分别获得大于94%和84%单 关键词： 单光子路由 单光子干涉 Sagnac单光子环形干涉仪 量子保密通信     

ʌ-type doubling and spin-rotation splitting of NO,measured in simultaneous one- and two-photon laser spectroscopy

Doppler-free two-photon excitation of NO A²Σ⁺ by visible dye laser radiation is recorded simultaneously with single-photon absorption of frequency-doubled UV laser light. The measurement of the frequency difference between corresponding lines in the one- and two-photon spectrum provides a new method for a direct optical determination of Λ-type doubling in the X²Π ground state. In addition, the spin-rotation splitting of the A²Σ⁺ excited state is resolved in the Doppler-free two-photon spectrum.     

Photon blockade in a cavity-atom optomechanical system

We study the single-photon blockade (1PB), two-photon blockade (2PB), and photon-induced tunneling (PIT) effects in a cavity-atom optomechanical system in which a two-level atom is coupled to a single-model cavity field via a two-photon interaction. By analyzing the eigenenergy spectrum of the system, 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. However, PIT often occurs in many cases when we consider 2PB in analogy to 1PB. In addition, we find that a 2PB region will present in the optomechanical system, which can be proved by calculating the correlation function of the model analytically.     

电光晶体调谐的外腔反馈半导体激光器

报道一种用电光晶体实现快速调谐和凋制激光频率的方法.在Littrow型外腔反馈半导体激光中插入LiNbO3晶体,利用LiNbO3晶体的电光效应,通过改变晶体电压来调节激光器的有效腔长,可以对激光频率进行快速的调谐和调制.采用该方法,自制外腔反馈半导体激光器的调谐频率可达到2 kHz,它的调谐范围为350 MHz,激光频率调谐系数约为1.06 MHz/V,用饱和吸收光谱观测频率调谐的效果.快速激光频率调制可以应用在稳频技术上,将外腔反馈半导体激光器调制在5～100 kHz频率下,均获得了87Rb原子D2线的饱和吸收光谱的色散信号,并实现了激光频率在饱和吸收峰上的长期稳定.     

The continuous wave electron paramagnetic resonance experiment revisited

When the modulation frequency used in continuous wave electron paramagnetic resonance (cw EPR) spectroscopy exceeds the linewidth, modulation sidebands appear in the spectrum. It is shown theoretically and experimentally that these sidebands are actually multiple photon transitions, sigma(+)+kxpi, where one microwave (mw) sigma(+) photon is absorbed from the mw radiation field and an arbitrary number k of radio frequency (rf) pi photons are absorbed from or emitted to the modulation rf field. Furthermore, it is demonstrated that both the derivative shape of the lines in standard cw EPR spectra and the distortions due to overmodulation are caused by the unresolved sideband pattern of these lines. The single-photon transition does not even give a contribution to the first-harmonic cw EPR signal. Multiple photon transitions are described semiclassically in a toggling frame and their existence is proven using second quantization. With the toggling frame approach and perturbation theory an effective Hamiltonian for an arbitrary sideband transition is derived. Based on the effective Hamiltonians an expression for the steady-state density operator in the singly rotating frame is derived, completely describing all sidebands in all modulation frequency harmonics of the cw EPR signal. The relative intensities of the sidebands are found to depend in a very sensitive way on the actual rf amplitude and the saturation of single sidebands is shown to depend strongly on the effective field amplitude of the multiple photon transitions. By comparison with the analogous solutions for frequency-modulation EPR it is shown that the field-modulation and the frequency-modulation technique are not equivalent. The experimental data fully verify the theoretical predictions with respect to intensities and lineshapes.     

The effects of tilt corrected residual aberration on the detection probability of single-photon propagation in a slant path turbulent atmosphere

Based on the assumption of a pulse laser beam with an initial Gaussian temporal shape and a collimated fundamental-model Gaussian beam, the Rytov approximation and Kolmogorov spectrum model for the index-of-refraction fluctuation of atmosphere, the effect of turbulence on the probability density, acquisition transmittance probability, transmittance probability density, acquisition probability of single-photon propagation in atmospheric communication channel with z-tilt and centroid-tilt aberration corrected are studied theoretically. The probability density, acquisition transmittance probability, transmittance probability density and acquisition probability models for single-photon propagation in uplink path and downlink path are derived. Our results shown that the detection probability and the acquisition transmittance probability of the single-photon are obvious increase, when the beams are propagation in the z-tilt corrected communication channel.     

Ferromagnetic to antiferromagnetic transition of one-dimensional spinor Bose gases with spin-orbit coupling

The effect of the interatomic dipole-dipole interaction on the single-photon transmission spectrum is investigated theoretically in the single-mode optical waveguide containing a pair of dipole interaction two-level atoms and the incident photon, respectively. The results show that the interatomic dipole-dipole interaction can induce a remarkable change in the photon-atom on-resonance frequency in the single-photon transmission spectrum compared with the nonexistence of the interatomic dipole-dipole interaction. As a consequence, the original zero transmission probability at the original photon-atom resonant frequency increases to one directly thanks to the appropriately-chosen dipole-dipole interaction strength. Consequently, this characteristic reveals that the interatomic dipole-dipole interaction treated as an important internal physical mechanism can perform as a functional quantum switching to manipulate the photon’s transmission in the optical waveguide. The corresponding interpretations responsible for this phenomenon are presented.