延长Rb原子退相干时间镀膜材料的可行性研究

实验测量了镀石蜡Rb池和石英玻璃Rb池中Rb原子自旋态寿命. 研究表明,镀石蜡Rb池的Rb原子自旋态寿命在温度T=50℃约为7　ms,而在同样温度的石英玻璃池中,Rb原子自旋态寿命仅为20 μs. 这为基于自旋的量子存储实验提供了很好的借鉴. 同时讨论了其他候选的材料来隔绝碱金属原子和容器壁的非弹性碰撞相互作用. 根据实验结果,我们认为H原子布于笼状结构内部的C₆₀H₆₀以及BN材料有较大的实用前景.     

自旋波波长对量子存储寿命的影响研究

利用电磁感应透明效应的动力学过程我们在87Rb冷原子系综中实验实现光学信号的存储和释放.通过改变信号光和耦合光的角度实现了自旋波波长的变化.在此基础上我们研究了存储寿命与自旋波波长的关系,结果表明,光存储寿命随自旋波波长(角度)的增加(减小)而增加,当自旋波波长大于2.2 mm(信号光和耦合光的角度小于0.02度)时,存储寿命可达到2.4 ms.     

读出效率对光与原子纠缠产生的影响

在光与原子纠缠态产生中,自旋波读出效率是影响纠缠质量的一个重要因素.本文在实验和理论上研究了读出效率与纠缠质量(Bell参量)的关系.实验上利用~(87)Rb冷原子系综中的自发Raman散射过程产生了光与原子量子纠缠.通过改变读光功率或OD (光学厚度),实现了读出效率的变化.在此基础上,研究了光与原子纠缠质量(Bell参量)随读出效率变化的关系.该实验将为高保真度的光与原子纠缠产生提供帮助.     

在时域实验研究扩散诱导的Ramsey压窄

基于Duan-Lukin-Cirac-Zoller(DLCZ)方案,在时域上研究了扩散诱导的Ramsey压窄.以87Rb热原子系综为研究对象,观测到缓冲气体,激光束尺寸和镀石蜡Rb池均可以导致Ramsey压窄现象.实验结果和文献中重复相互作用模型预期的一致.     

Rb原子激发态碰撞能量转移

报道了用连续单模激光激发Rb原子至特定的激发态，从而观察激发态间的碰撞形成更高Rb原子激发态的实验结果.实验观察到Rb原子激发态的自发辐射与高激发态的碰撞形成通道之间的明显竞争，测得了高激发态的形成概率与激发光功率、原子蒸气温度及激光失谐的关系，所提出的碰撞能量转移机理较好地解释了实验结果. 关键词：     

从费米原子到配对超冷分子

自从1995年以来，实验物理学家已经在一系列玻色原子气系统中实现了玻色—爱因斯坦凝聚(BEC)，它们是^1H，^7Li，^23Na，^85Rb和^87Rb等等，这些玻色原子具有整数自旋量子数，与玻色原子相对应的是费米原子，它们具有半整数的自旋值，例如^40K。即使在非常接近绝对零度的低温下，费米原子气也不可能凝聚到单一量子态：每一个费米原子所     

在时域实验研究扩散诱导的Ramsey压窄

基于Duan-Lukin-Cirac-Zoller(DLCZ)方案,在时域上研究了扩散诱导的Ramsey压窄. 以⁸⁷Rb热原子系综为研究对象,观测到缓冲气体,激光束尺寸和镀石蜡Rb池均可以导致Ramsey压窄现象. 实验结果和文献中重复相互作用模型预期的一致.     

Rb(7S-5D)-H2,He能量转移截面与温度的关系

脉冲激光双光子激发Rb(5S)态到Rb(5D)或Rb(7S)态,在样品池条件下,利用原子荧光光谱方法测量了Rb(7S-5D)-H2,He碰撞能量转移截面与池温的关系.利用三能级模型的速率方程分析.通过测量在不同H2或He密度下的直接荧光与转移荧光的时间积分强度比,在353～493 K温度范围内得到了Rb(7S-5D)-H2,He的反应与非反应碰撞能量转移截面.对于Rb(7S)+H2→Rb(5D)+H2,其转移截面随温度的增加而减小,而其逆过程的转移截面则随温度的增加而增加.对于与He的碰撞,在不同温度下7S-5D的转移截面均符合细致平衡原理,7S,5D态与H2的碰撞速率系数是反应与非反应速率系数之和,利用实验数据可以分别确定反应与非反应截面,7S态的平均反应截面与5D态平均反应截面之比约为1.5.Rb(7S)与H2的反应活动性大于Rb(5D).     

玻色-爱因斯坦凝聚(BEC)实验及其最新进展

近年来,有关玻色-爱因斯坦凝聚(BEC)的实验研究得到了快速发展,并取得了一系列重大的实验进展。本文重点介绍了玻色-爱因斯坦凝聚的实验结果及其最新进展,主要包括具有正、负散射长度碱金属(7Li,23Na,41K,85Rb,87Rb和133Cs)原子BEC的实现,自旋极化1H原子、亚稳态4He原子和具有2个价电子的174Yb稀土原子BEC的实现,全光型BEC和微阱BEC乃至低维BEC的实现,甚至分子BEC和费米原子对的凝聚以及超冷BEC凝聚体的应用等。     

高激发态原子间的范德瓦尔斯相互作用

与基态原子相比,高激发态原子(主量子数n15)具有很强的长程范德瓦尔斯(Van der Waals)相互作用,这种强相互作用可以阻止相邻原子的进一步激发,产生激发阻塞效应.本文从理论上利用微扰方法计算碱金属原子Rb和Cs激发态nS,nD原子对态的相互作用,获得原子相互作用的色散系数并分析了原子间的长程相互作用特性.结果表明,Rb和Cs原子的nS态表现为排斥相互作用,而nD态原子L=0时,Rb原子表现为吸引作用,Cs原子表现为排斥作用.     

Slow spin relaxation of Rb atoms confined in glass cells filled with dense 4He gas at 1.85 K

At temperatures below 2.1 K, long-lived gaseous Rb atoms in glass cells have been generated with a simple method: irradiating the cells, containing 4He gas and Rb metal, with a cw laser. The obtained atomic Rb density ( approximately 10(8) cm(-3)) decreases with a 1/e time constant of about 10 s at 1.85 K. We have performed optical pumping of the Rb atoms and measured the longitudinal electronic spin relaxation time at 1.85 K as well. For processes (such as Rb-He collisions) which do not remove the atomic Rb from the vapor, this relaxation time is found to be about 60+/-15 s.     

Improvement of the spin polarization lifetime in the 85Rb vapor cell by octadecyltrichlorosilane coating

Effective surface coatings allow for long spin polarization in alkali metal cells, suppressing the magnetic field gradient effect and providing an improvement in atomic magnetometer sensitivity. In this work, the effect of an octadecyltrichlorosilane (OTS) surface coating on the longitudinal and transverse spin polarization lifetime of an optically pumped ⁸⁵Rb vapor cell has been studied. Our results showed that the spin polarization lifetime significantly increased in the OTS lined cell compared to the unlined cell. The relaxation rate due to alkali metal atoms wall collisions and the magnetic field gradient has been decreased by using an OTS surface coating. A longer spin polarization lifetime in the lined cell causes a narrower magnetic resonance line width and subsequently a more sensitive atomic magnetometer.     

Spontaneous dissociation of long-range Feshbach molecules

We study the spontaneous dissociation of diatomic molecules produced in cold atomic gases via magnetically tunable Feshbach resonances. We provide a universal formula for the lifetime of these molecules that relates their decay to the scattering length and the loss rate constant for inelastic spin relaxation. Our universal treatment as well as our exact coupled channels calculations for 85Rb dimers predict a suppression of the decay over several orders of magnitude when the scattering length is increased. Our predictions are in good agreement with recent measurements of the lifetime of 85Rb(2).     

Magnetically tuned spin dynamics resonance

We present the experimental observation of a magnetically tuned resonance phenomenon in the spin mixing dynamics of ultracold atomic gases. In particular, we study the magnetic field dependence of spin conversion in F=2 (87)Rb spinor condensates in the crossover from interaction dominated to quadratic Zeeman dominated dynamics. We discuss the observations in the framework of spin dynamics as well as matter wave four wave mixing. Furthermore, we show that the validity range of the single mode approximation for spin dynamics is significantly extended at high magnetic field.     

Efficiency of photodesorption of Rb atoms collected on polymer organic film in vapor-cell

The efficiency of photodesorption of Rb atoms previously collected on polymer organic film has been studied in detail. This study was carried out in a Pyrex glass cell of which the inner surface was covered with (poly)dimethylsiloxane (PDMS) film and illuminated by a powerful flash lamp. The desorption dynamic of the Rb atoms density in the cell caused by the illumination and percentage of desorbed atoms was studied by using of Rb resonance lamp and free running diode laser as sources of probing light. It was determined that 85 percent collected chemical active Rb atoms and stored during 16 s in the closed cell, 75 percent in the pumped cell can be desorbed by single flash of the lamp. The number of stored atoms decays with a characteristic time of 60 min in isolated cell and with a time 12.4 min in a pumped cell. We believe that this efficient method of collection and fast realization of atoms or molecules could be used for enhancement of sensitivity of existed sensors for the trace detection of various elements (including toxic or radioactive ones) which is important to environmental applications, medicine or in geology. The effect might help to construct an efficient light-driven atomic source for a magneto-optical trap in a case of extremely low vapor density or very weak flux of atoms, such as artificial radioactive alkali atoms.     

Experimental evaluation of rate coefficients for Rb（5Dj）＋H2→ RbH＋H reaction

The Rb（5Dj）＋H2→RbH＋H photochemical reaction has been studied. Rb vapor mixed with H2 is irradiated in a glass cell with 778-nm pulses which populate one of the 52D states by two-photon absorption. Measurements for the relative intensities of the atomic fluorescence and the absorption of the RbH product near the axis of the cell yield the rate coefficients for the Rb（5D3/2）＋H2 and Rb（5D5/2）＋H2 reactions, which are （3.6±1.3） ×10^-11 and （1.7±0.6）×10^-11 cm^3/s, respectively. The relative reactivity with H2 for Rb（5D3/2） is higher than that for Rb（5D5/2）.     

Spontaneous macroscopic spin polarization in independent spinor Bose-Einstein condensates

We present experimental evidence for the spontaneous formation of a macroscopic spin polarization in overlapping regions of two independent Bose-Einstein condensates produced in different hyperfine states of 87Rb. The condensates are independent in the sense that we do not explicitly introduce a relative phase between them. A single "spin-tip" pulse maps the transverse spin polarization into longitudinal spin polarization, and the atomic density distributions are measured with a Stern-Gerlach imaging method. The resulting matter-wave interference patterns are anticorrelated.     

全光学高灵敏度铷原子磁力仪的研究

报道了一种全光学的高灵敏度铷原子磁力仪.其原理是基于激光束与处于微弱磁场中的铷原子的相互作用.这种相互作用与铷原子所处的环境中的磁场有关,因而通过测量透过铷原子气体的激光强度的变化可以获得磁场信息.分析了该磁力仪的工作原理,建立了相应的实验装置,并对其性能进行了测试.结果表明实验结果与理论相符合.进一步研究了影响磁力仪灵敏度的一些因素,提出了优化各参数来提高磁力仪灵敏度的方法.     

Observation of time correlation function of multimode two-photon pairs on a rubidium D2 line

We report on the generation of a type-I multimode two-photon state on a rubidium D(2) line (780 nm) using periodically poled KTiOPO(4) crystals. With a degenerate optical parametric oscillator far below threshold, we observe an oscillatory correlation function; the cross correlation between two photons shows a cavity bandwidth of about 7.8 MHz. We also use a Fabry-Perot etalon to filter its most longitudinal modes and observe its time correlation function. The experimental data are well fitted to theoretical curves. This system could be utilized for demonstrating storage and retrieval of narrow-band photons in Rb atomic ensembles, which is important for long-distance quantum communication.     

Frequency Stability of Atomic Clocks Based on Coherent Population Trapping Resonance in ^85Rb

An atomic clock system based on coherent population trapping （CPT） resonance in 85Rb is reported, while most past works about the CPT clock are in ST Rb. A new modulation method （full-hyperfine-frequency-splitting modulation） is presented to reduce the effect of light shift to improve the frequency stability of the CPT clock in SSRb. The experimental results show that the short-term frequency stability of the CPT clock in SSRb is in the order of 10^-10/s and the long-term frequency stability can achieve 1.5 × 10^-11/80000s, which performs as well as 87 Rb in CPT resonance. This very good frequency stability performance associated with the low-cost and low-power properties of SSRb indicates that an atomic clock based on CPT in SSRb should be a promising candidate for making the chip scale atomic clock.