共查询到20条相似文献,搜索用时 15 毫秒
1.
薛定谔猫态是一类重要的非经典光场,实验上可以通过真空压缩态减光子的方案获得.本文从理论上研究了实验条件对制备薛定谔猫态的影响,主要考虑了包括压缩态的压缩度和纯度、单光子探测器的效率及噪声以及零拍探测器的效率等诸多因素的影响.理想情况下通过减光子方案制备得到的薛定谔猫态为奇光子数态,其相空间原点的Wigner函数为负值是其非经典特性的重要判据,而保真度可以度量制备态与理想猫态之间的相似程度.在压缩态为非纯态以及单光子探测器为商用低效率阈值探测器的情况下,计算了制备猫态的保真度、Wigner函数及其相空间原点处W(0)的表达式,分析了实验条件对薛定谔猫态制备的影响,为制备高质量的薛定谔猫态提供了理论指导. 相似文献
2.
The quantum theory of dark soliton propagation in fibers is studied based on the linearization approximation. Then the uncertainties in photon number, phase, position (time) and momentum of quantized dark solitons are calculated. Finally, the squeezing of the dark soliton is investigated by using homodyne detection and compared with bright soliton case. 相似文献
3.
We report new experiments on polarization squeezing using ultrashort photonic pulses in a single pass of a birefringent fiber. We measure what is to our knowledge a record squeezing of -6.8+/-0.3 dB in optical fibers, which when corrected for linear losses is -10.4+/-0.8 dB. The measured polarization squeezing as a function of optical pulse energy, which spans a wide range from 3.5-178.8 pJ, shows a very good agreement with the quantum simulations, and for the first time we see the proof experimentally that Raman effects limit and reduce squeezing at high pulse energy. 相似文献
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碱金属原子是光量子存储的良好介质,与碱金属原子共振的非经典光场是量子信息处理的重要资源.本文采用周期极化磷酸氧钛晶体作为非线性介质,利用参量振荡过程产生了795 nm(铷原子D1线)的真空压缩光场.通过对平衡零拍探测系统的时域信号进行采集,得到压缩光场不同相位角下的噪声分布;利用极大似然估计法对压缩光场进行了态重构,得到了密度矩阵及相空间的Wigner函数.理论计算了真空压缩场的光子数分布和Wigner函数,并对理论计算结果和极大似然重构结果进行了分析和比较. 相似文献
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与运动原子相互作用的场的压缩效应 总被引:1,自引:1,他引:0
采用量子光学中时间演化算符方法,研究了与运动原子相互作用的场的压缩效应,揭示了光场的初始平均光子数和场模结构参数对光场压缩特性的影响,结果表明:适当选择系统参数,可获得在时间上持续压缩的压缩光。 相似文献
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构造了光场算符n次幂叠加激发混沌场,采用数值计算方法研究了该量子态的压缩效应、反聚束效应和统计性质,讨论了混沌场平均光子数、算符叠加系数及其幂次n对量子特性的影响.研究结果表明:光场算符n次幂叠加激发混沌场不呈现压缩效应,但呈现出反聚束效应和亚泊松分布性质,并且随平均光子数增大,它的反聚束效应和亚泊松分布性质减弱;随着算符组合部分中产生算符的比重增大,光场反聚束效应和亚泊松分布性质增强;随着算符幂次增大,亚泊松分布性质加强. 相似文献
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运用全量子理论并结合数值计算方法,研究了处于真空库和热库中原子系统的偶极压缩特性,讨论了原子的初态以及热库的平均光子数对原子偶极压缩特性的影响.研究表明:真空库中,初始处于基态和激发态的叠加态原子,当激发态的粒子布居概率少于基态时,原子的偶极压缩无限接近于零而永远不消失;反之,原子的偶极压缩将在有限的时间内消失;热库中,不管原子初始处于什么态,其偶极压缩都在有限的时间内消失,并且随着热库的平均光子数的增大而消失得越快。 相似文献
11.
We study the quantum fluctuations of an optical nonlinear Schr?dinger soliton after spectral filtering. The photon-number-bandwidth correlation of the emerging soliton produces squeezing in the photon number of the filtered soliton. Bandwidth oscillations caused by the interference of the soliton with the quantum-noise continuum, however, give oscillations of the photon-number squeezing and, in addition, prevent achievement of arbitrarily high values of squeezing through spectral filtering. 相似文献
12.
The Squeezing and sub-poissonian photon statistics of an optical field are a purely quantum mechanical phenomenon and has
been accepted as means of achieving noise below the quantum shot-noise limit. The effect of higher-order squeezing and sub-poissonian
nature of an optical field in coherent anti-Stokes Raman scattering (CARS) and coherent anti-Stokes hyper Raman scattering
(CAHRS) are investigated under short-time approximation. The coupled Heisenberg equations of motion involving real and imaginary
parts of the quadrature operators are established and solved under short-time scale. The dependence of squeezing on the number
of photons is also investigated. It is also shown that higher-order squeezing allows a much larger fractional noise reduction
than lower-order squeezing. The occurrence of amplitude squeezing effects of the radiation field in the fundamental mode is
investigated in both the processes. The present work shows that squeezing is greater in CAHRS than the corresponding squeezing
in CARS. It is also shown that squeezing is greater in stimulated process than corresponding squeezing in spontaneous interaction.
The conditions for obtaining maximum and minimum squeezing are obtained. The photon statistics of the pump mode in the processes
has also been investigated and found to be sub-poissonian in nature. 相似文献
13.
利用全量子理论,在非旋波近似下,对与级联型三能级原子相互作用的二项式光场的光场压缩效应和原子布居几率进行了精确求解.讨论了二项式光场参量η对光场压缩效应的影响,同时也讨论了二项式态光场的最大光子数M对原子布居几率的影响.数值计算结果表明:随着二项式光场参量η的增大,光场压缩效应的持续时间先增大后减小.在非旋波近似下,由于虚光子的影响,光场压缩效应的演化曲线出现了“小锯齿状”的振荡;随着二项式光场的最大光子数M的增大,原子布居几率回复塌缩周期逐渐增大,并且原子布居几率在塌缩区不能完全塌缩,而是出现了“小锯齿状”的振荡.另外文中也讨论了非旋波项对系统量子特性的影响. 相似文献
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利用全量子理论,在非旋波近似下,对与级联型三能级原子相互作用的二项式光场的光场压缩效应和原子布居几率进行了精确求解.讨论了二项式光场参量η对光场压缩效应的影响,同时也讨论了二项式态光场的最大光子数M对原子布居几率的影响.数值计算结果表明:随着二项式光场参量η的增大,光场压缩效应的持续时间先增大后减小.在非旋波近似下,由于虚光子的影响,光场压缩效应的演化曲线出现了"小锯齿状"的振荡;随着二项式光场的最大光子数M的增大,原子布居几率回复塌缩周期逐渐增大,并且原子布居几率在塌缩区不能完全塌缩,而是出现了"小锯齿状"的振荡.另外文中也讨论了非旋波项对系统量子特性的影响. 相似文献
15.
LIUXiao-Juan FANGMao-Fa 《理论物理通讯》2004,42(1):103-109
From a quantum information point of view we investigate the entropy squeezing properties for a two-level atom interacting with the two-mode coherent fields via the two-photon transition. We discuss the influences of the initial state of the system on the atomic information entropy squeezing. Our results show that the squeezed component number, squeezed direction, and time of the information entropy squeezing can be controlled by choosing atomic distribution angle, the relative phase between the atom and the two-mode field, and the difference of the average photon number of the two field modes, respectively. Quantum information entropy is a remarkable precision measure for the atomic squeezing. 相似文献
16.
LIU Xiao-Juan FANG Mao-Fa 《理论物理通讯》2004,42(7)
From a quantum information point of view we investigate the entropy squeezing properties for a two-level atom interacting with the two-mode coherent fields via the two-photon transition. We discuss the influences of the initial state of the system on the atomic information entropy squeezing. Our results show that the squeezed component number,squeezed direction, and time of the information entropy squeezing can be controlled by choosing atomic distribution angle,the relative phase between the atom and the two-mode field, and the difference of the average photon number of the two field modes, respectively. Quantum information entropy is a remarkable precision measure for the atomic squeezing. 相似文献
17.
J. Milanovic J. Heersink Ch. Marquardt A. Huck U. L. Andersen G. Leuchs 《Laser Physics》2007,17(4):559-566
We report on the generation of polarization squeezing by employing intense, ultrashort light pulses in a single pass method
in photonic crystal fibers. We investigated the squeezing behavior near the zero-dispersion wavelength and in the anomalous
dispersion regime by using two distinct fibers. We observed a maximal squeezing at 810 nm of −3.3 ± 0.3 dB with an excess
noise of +16.8 ± 0.3 dB in the anomalous regime. Correcting for linear and interference losses between the polarization modes,
this corresponds to −6 ± 1 dB. The ratio of squeezing to excess noise indicates the creation of a much purer state; this ratio
indeed lies an order of magnitude below those squeezing experiments that exploit traditional fibers [1]. We attribute this
increased state of purity to increased effective nonlinearity and to the reduction of scattering on acoustic modes in the
fiber.
Original Text ? Astro, Ltd., 2007. 相似文献
18.
将拉盖尔多项式算符作用在相干态上,构造了拉盖尔多项式算符激发相干态.利用有序算符积分技术,导出了它的归一化系数以及〈a^la^+m〉的计算表达式.采用数值计算方法,讨论了相干态相位角和平均光子数对它的非经典性质的影响.研究结果表明:一阶拉盖尔多项式算符激发相干态呈现出压缩效应、反聚束效应、亚泊松分布和Wigner函数负性等量子特性,并且相干态的相位角对它的量子特性有重要影响;另一方面,随相干态平均光子数增大,它的反聚束效应和亚泊松分布性质逐渐减弱,压缩效应和Wigner函数的负性却先增强,而后又逐渐减弱. 相似文献
19.
Eight-wave mixing is a process which involves absorption of four pump photons and emission of three probe photons of same
frequency and a signal photon of different frequency. Squeezing is investigated in the fundamental mode in spontaneous and
stimulated eight-wave mixing process using quantum mechanical approach. The presence of squeezing in field amplitude, amplitude-squared
and amplitude-cubed in the fundamental mode has been probed. The dependence of squeezing on photon number is established with
investigations into degree of squeezing in the first and higher order of field amplitude. The photon statistics of the field
in the fundamental mode has also been investigated. It has been found that the field shows sub-Poissonian behaviour in the
fundamental mode. 相似文献
20.
Neergaard-Nielsen JS Nielsen BM Hettich C Mølmer K Polzik ES 《Physical review letters》2006,97(8):083604
We report on the experimental observation of quantum-network-compatible light described by a nonpositive Wigner function. The state is generated by photon subtraction from a squeezed vacuum state produced by a continuous wave optical parametric amplifier. Ideally, the state is a coherent superposition of odd photon number states, closely resembling a superposition of weak coherent states |alpha > - |-alpha >. In the limit of low squeezing the state is basically a single photon state. Light is generated with about 10,000 and more events per second in a nearly perfect spatial mode with a Fourier-limited frequency bandwidth which matches well atomic quantum memory requirements. The generated state of light is an excellent input state for testing quantum memories, quantum repeaters, and linear optics quantum computers. 相似文献