冷原子系综内单量子态相干操控

发布时间：2018-01-05 12:24

本文关键词：冷原子系综内单量子态相干操控　出处：《中国科学技术大学》2016年博士论文　论文类型：学位论文

【摘要】：量子存储是量子信息领域的重要组成部分,其在远距离量子通信、光学量子计算、量子测量等众多研究领域都有重要的应用。近年来,量子存储器的研究获得越来越多的关注,在不同的体系中取得了许多重要的研究成果。从目前国内外的研究成果来看,基于冷原子系综的量子存储器发展较为迅速,在长寿命高效率等综合性能方面获得长足发展。在冷原子系综存储器中,对单量子态的相干操控在提升存储器性能、实现量子操控等方面有着重要的作用,而对这方面的实验研究还需要进一步的发展。本论文的主要工作就是对基于冷原子系综量子存储器内自旋波相干操控的相关实验研究。我们首先利用拉曼双光子跃迁技术,首次在基于系综的量子存储器中实现自旋回波技术来抑制自旋波退相干,将存储器寿命提升至毫秒量级,并通过深入研究有限π脉冲精度引起的噪声的分布,从实验上弥合先前两种理论预言的矛盾。接下来,由于自旋回波技术对回波脉冲的精度有非常高的要求,我们对上述方案进行了改进,利用双光子拉曼跃迁将存储的自旋波态翻转至另外一个自旋波态,且将自旋波的相位擦除,自旋波的退相干被冻结,将不同角度的存储寿命提升一个量级,达到原子扩散引起的寿命极限,并且,由于该方案不涉及布居数的反转,因此对π脉冲的精度要求不高,存储器的量子品质得到很好的保持(g220)。另外,除了通过调控自旋波实现存储寿命的增长,我们成功的结合拉莫尔进动和拉曼跃迁技术首次在冷原子系综的量子存储器中实现对存储的单自旋量子比特的高保真度的任意旋转操作,并成功实现了几种特殊的单比特门操作。最后,我们利用驻波光场产生具有空间分布的拉曼拉比振荡的方法,在实验上成功的验证了一种高精度量子光刻方案的正确性,结合高分辨成像等一系列技术,成功突破衍射极限,在半个波长内成功观测到9条原子条纹,突破衍射极限9倍以上。同时,我们利用多脉冲结合的方式实现原子的局域化操作,最终观测到的原子的宽度为驻波场半波长的1/7。本论文中这些对自旋波的一系列操控,丰富了对原子系综的量子存储器中量子态相干操控的技术方法,提升了存储器的综合性能,对未来量子中继、远距离量子通信以及线性光学量子计算等一系列量子信息领域的发展都有重要的作用。
[Abstract]:Quantum storage is an important part of quantum information field. It has important applications in many research fields such as long-distance quantum communication, optical quantum computing, quantum measurement and so on. More and more attention has been paid to the study of quantum memory, and many important research results have been obtained in different systems. The quantum memory based on cold atom ensemble is developing rapidly and has made great progress in long life and high efficiency. Coherent manipulation of single quantum states plays an important role in improving memory performance and realizing quantum manipulation. The main work of this thesis is to study the coherent manipulation of spin wave in the cold atomic ensemble quantum memory. Firstly, we use Raman two-photon. Transition technology. It is the first time to realize spin echo technology in ensemble based quantum memory to suppress spin wave decoherence, to increase memory lifetime to millisecond order, and to study the distribution of noise caused by finite 蟺 pulse precision. From the experiment, the contradiction between the two theoretical predictions is bridged. Then, due to the very high precision of the spin echo technology, we improve the above scheme. The stored spin wave state is flipped to another spin wave state by two-photon Raman transition, and the phase of the spin wave is erased, the decoherence of the spin wave is frozen, and the storage life of different angles is increased by one order of magnitude. The lifetime limit caused by atomic diffusion is reached, and the precision of 蟺 pulse is not high because the population inversion is not involved in this scheme. The quantum quality of the memory is maintained very well. In addition, the memory life is increased by regulating spin waves. It is the first time that we have successfully realized the arbitrary rotation of the high fidelity of the stored single spin quantum bits in the cold atom ensemble quantum memory by combining the Lamolian precession and Raman transition techniques. Several special single-bit gate operations are successfully implemented. Finally, we use the standing wave light field to generate raman oscillation with spatial distribution. The correctness of a high precision quantum lithography scheme is verified in the experiment. In combination with a series of techniques such as high resolution imaging, the diffraction limit is successfully broken, and 9 atomic fringes are observed successfully in half a wavelength. At the same time, we use multi-pulse combination to realize the localization of atoms. Finally, the width of the observed atom is 1 / 7 of the half-wavelength of standing wave field. In this paper, a series of manipulations of spin waves enrich the technical methods of quantum state coherent manipulation in the atomic ensemble quantum memory. It improves the comprehensive performance of memory and plays an important role in the future quantum relay, long-distance quantum communication, linear optical quantum computing and a series of quantum information development.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O413;TP333

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