共查询到20条相似文献,搜索用时 187 毫秒
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《Physics letters. A》1998,244(6):507-511
Two-photon or biphoton interference has been studied extensively for CW and single pulse pumped spontaneous parametric downconversion (SPDC). In this paper we examine biphoton interference between amplitudes originating in different pump pulses. This novel effect arises from the coherence of the pump pulses. The interference has a natural interpretation in terms of indistinguishability of various Feynman alternatives. 相似文献
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本文利用光栅单色仪实现了对超短脉冲抽运周期极化磷酸氧钛钾晶体产生的通信波长频率一致纠缠光子源的频谱特性分析.测量到双光子的联合频谱呈正关联分布,为频率一致纠缠光源.信号光、闲置光中心波长分别为1574.4 nm和1574.9 nm,频谱宽度分别为35.3 nm和37.6 nm,双光子符合包络宽度约为3 nm.根据单光子频谱宽度与双光子符合包络宽度的比值可以得到双光子的频率纠缠参量R约为12,表征了信号光子与闲置光子之间具有较高的频率纠缠度. 相似文献
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利用自发参量下转换过程产生的频率纠缠光源在量子信息处理及相关领域中 具有十分重要的应用. 本文利用中心波长为792 nm, 脉冲宽度小于20 fs的脉冲激光源抽运满足II类准相位 匹配条件的周期极化磷酸氧钛钾晶体, 实验产生了偏振相互正交的频率一致纠缠光子对. 基于Hong-Ou-Mandel干涉仪的二阶量子符合干涉装置, 测量到该纠缠双光子对的干涉可见度约为42%, 表明其频率不可分特性较理想频率一致纠缠光源大大降低. 通过理论分析给出, 由于超短脉冲光源对应的宽频谱带宽影响, 相位匹配函数中的高阶色散项不再忽略, 从而导致纠缠光子对的频率不可分性减弱. 进一步利用实验参数给出的数值模拟结果与实验结果符合, 证实了脉冲抽运源带宽对频率一致纠缠光源的量子不可分特性的影响.
关键词:
频率一致纠缠
Hong-Ou-Mandel干涉测量
符合计数 相似文献
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V. P. Karassiov 《Journal of Russian Laser Research》1994,15(5):391-401
The concept of squeezing is discussed for multimode quantum light beams with consideration of polarization using the polarization gaugeSU (2) invariance of free electromagnetic fields. We separate the polarization and biphoton degrees of freedom from other ones, and consider uncertainty relations characterizing polarization and biphoton observables. As a consequence, we obtain a new classification of polarization states of light within quantum optics. We also discuss briefly some interrelations of our analysis with experiments related to some fundamental problems of physics. 相似文献
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Spontaneous parametric downconversion (SPDC) is widely used to generate entangled photon pairs; however, multi-pair emissions degrade the quality of the entanglement. We numerically evaluate polarization-entangled photon pairs created by SPDC. The effects of multi-pair emission events on the visibility of two-photon interference and on the fidelity (the probability overlap for ideal and real states) are analyzed using single-photon detectors that can count the number of incoming photons and discard multiphoton events. Compared with conventional threshold single-photon detectors, photon-number resolving single-photon detectors have higher fidelity for the same or lower visibility. 相似文献
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A method for generating two-photon wave packets (biphotons) with a small width of the spatial intensity correlation function
(correlation radius) has been considered. We propose to prepare a two-photon wave packet inhomogeneously broadened in the
angle by means of spontaneous parametric down-conversion in an inhomogeneous crystal. Such biphotons are not diffraction limited;
i.e., their correlation radius is much larger than the inverse width of the spatial spectrum. However, the correlation radius
of such a biphoton decreases as the biphoton propagates in free space, and transverse compression occurs at a certain distance
from the crystal; i.e., the biphoton becomes diffraction limited. 相似文献
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理论研究了周期极化铌酸锂晶体中通过自发参量下转换产生的纠缠双光子的波长管理方法.简并自发参量下转换产生的单色偏振纠缠双光子的波长,可以通过调整晶体的极化周期或工作温度自由地调节,特别是在加工好的晶体中极化周期是确定的,因而调整晶体的工作温度更加便捷.对于双色偏振纠缠双光子来说,不需改变入射的泵浦光以及晶体的极化结构,仅通过调节晶体的工作温度就可以实现o光光子和e光光子波长的严格交换. 相似文献
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Nonlocal shaping effects in the time or spectral profiles of an entangled photon pair emerging from a pulsed parametric down-converter are observed by spectrally or temporally filtering one of the twin beams. In particular, we demonstrate the appearance of fourth-order ("ghost") interference fringes in the spectrum of one beam conditioned by photodetection at the output of an unbalanced Michelson interferometer placed in the path of the other beam. The coherence time of the pump is the limiting factor for the sharpness of the details in the shaped biphoton spectrum. 相似文献
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V. P. Karassiov 《Journal of Russian Laser Research》2005,26(6):484-513
The notion and main features of polarization states of light are discussed within the framework of classical and quantum optics.
This notion is shown to be correctly defined for arbitrary light beams only within quantum optics by using the P-quasispin formalism developed earlier. Polarization states of quantum light are shown to be fully described by a polarization
density operator (PDO) obtained via reducing the total field density operator. Theoretical foundations are given for quantum
tomography of polarization states of light fields considered as a way of measuring PDO. Herewith, the main attention is paid
to a method where proper polarization tomographic observables (PDO “measurers”) are used. The method is shown to be adequately
formulated by means of quasi-spectral tomographic expansions of PDO in special operator bases (given by finite sums of partially
orthogonal projectors), which determine probability distributions of tomographic observables as expansion coefficients. Matrix
versions of such “tomographic” PDO representations are obtained. In particular, projections of these expansions on quasiclassical
operator bases, determining polarization quasiprobability functions, are given. An example of experimental implementation
of polarization tomography of unpolarized light (biphoton radiation with hidden polarization) is analyzed. 相似文献
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P. A. Apanasevich A. A. Kananovich A. A. Demidovich M. B. Danailov V. A. Orlovich 《Journal of Applied Spectroscopy》2011,78(1):43-49
Output power dependences of composite Nd3+:YVO4 Raman laser stationary generation on the longitudinal diode pump power are measured at different transmissions of the output
mirror at the Stokes radiation frequency. The deviation of the measured dependences from linear is explained by the influence
of thermal effects on both the overlap of the beams and diffraction losses. A method to estimate the laser and Stokes losses
in the cavity and the parameters characterizing the overlap of the laser radiation with the pump and Stokes beams is proposed.
A Stokes-component of power 2.1 W is obtained and corresponds to 12% diode-to-Stokes efficiency. 相似文献
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A theory is presented for the quantum state of photon pairs generated from spontaneous parametric down-conversion nonlinear
process. In this theory, the influence of the final sizes of nonlinear optical crystals on optical eigenmodes is explicitly
taken into consideration. It was found that these photon pairs are not in entangled quantum states. Polarization correlations
between the signal beam and the idler beam are explained. It is also shown that the two photons generated from SPDC are not
spatially separated, therefore the polarization correlation between the signal and idler beams is not an evidence for quantum
non-locality.
The text was submitted by the authors in English. 相似文献
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We have numerically investigated the biphoton generation rate as a function of several parameters in the spontaneous four-wave mixing in cold atoms.It has been found that the biphoton generation rate can easily reach saturation with the intensity of the coupling laser increasing.The saturation intensity is mainly dependent on the dephasing rate of the ground states,unrelated to the pumping laser.It implies that though the biphoton waveform can be manipulated by the coupling laser,the generation rate of the biphoton cannot increase markedly after the saturation.The saturation effect also suggests that there is an optimal coupling laser for obtaining the largest biphoton generation rate with a sufficiently long coherence time. 相似文献
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《中国光学快报(英文版)》2015,(11)
We present a simple, robust, space-adjustable dark magneto-optical trap(MOT) for the efficient production of heteronuclear molecules. Double-mixed beams made up of repumping beams and depumping beams propagate in nearly opposite directions in the dark MOT. This optical arrangement can easily adjust the spatial positions of two clouds by changing the power ratio of the two repumping beams, and ensure a good overlap, which is very necessary for the production of heteronuclear molecules. The imaging of cold atoms by camera and the collisioninduced loss rate obtained by recording the loading curve of the cold atoms show that we obtain a perfect overlap of atom clouds. The number of Rb Cs molecules with the double-mixed beams is improved by 70%, which is higher than the one with the single-mixed beam. 相似文献
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Christophe Couteau 《Contemporary Physics》2018,59(3):291-304
Spontaneous Parametric Down-Conversion (SPDC), also known as parametric fluorescence, parametric noise, parametric scattering and all various combinations of the abbreviation SPDC, is a non-linear optical process where a photon spontaneously splits into two other photons of lower energies. One would think that this article is about particle physics and yet it is not, as this process can occur fairly easily on a day to day basis in an optics laboratory. Nowadays, SPDC is at the heart of many quantum optics experiments for applications in quantum cryptography, quantum simulation, quantum metrology but also for testing fundamentals laws of physics in quantum mechanics. In this article, we will focus on the physics of this process and highlight a few important properties of SPDC. There will be two parts: a first theoretical one showing the particular quantum nature of SPDC, and the second part, more experimental and in particular focusing on applications of parametric down-conversion. This is clearly a non-exhaustive article about parametric down-conversion as there is a tremendous literature on the subject, but it gives the necessary first elements needed for a novice student or researcher to work on SPDC sources of light. 相似文献
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The main methods for controlling the biphoton field, as well as the problems for which the width and the shape of the spectrum
of the biphoton field are of decisive importance, are discussed. The method for controlling the spectrum of the spontaneous
parametric downconversion of light based on the spatial modulation of the refractive indices of a nonlinear crystal in which
the generation of biphotons has been analyzed. Modulation is due to the thermo-optic and electro-optic effects. 相似文献
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We have generated a new type of biphoton state by cavity-enhanced down-conversion in a type-II phase-matched, periodically poled KTiOPO4 crystal. By introducing a weak intracavity birefringence, we obtained signal and idler photons whose quantum interference was modulated between singlet and triplet signatures according to their arrival-time difference. This cavity-enhanced biphoton source is spectrally bright, yielding a single-mode fiber-coupled coincidence rate of 0.7 pairs/s per mW of pump power per MHz of down-conversion bandwidth. 相似文献
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Spontaneous parametric down-conversion (SPDC) in media with no inversion center and the use of this phenomenon in the spectroscopy of natural oscillation states of a crystal lattice (i.e., optical phonons) are retrospectively described. We think that the SPDC spectroscopy method is estimated inappropriately and hope to again attract the attention of readers to one of the most interesting quantum phenomena of nonlinear optics that has no classical analog. The capabilities of SPDC spectroscopy will certainly be used in both fundamental science and technology of new materials. 相似文献