量子算法与量子计算实验

从量子体系的基本特性出发 ,介绍了量子计算的基本概念和物理背景 ,系统阐述了几种主要的量子算法以及量子计算在实验方面的发展现状。对比经典计算机 ,讨论了量子计算机的优越性、实现量子计算的困难和以期克服的途径。     

中性原子量子计算研究进展

相互作用可控、相干时间较长的中性单原子体系具备在1 mm2的面积上提供成千上万个量子比特的规模化集成的优势,是进行量子模拟、实现量子计算的有力候选者.近几年中性单原子体系在实验上取得了快速的发展,完成了包括50个单原子的确定性装载、二维和三维阵列中单个原子的寻址和操控、量子比特相干时间的延长、基于里德伯态的两比特量子门的实现和原子态的高效读出等,这些工作极大地推动了该体系在量子模拟和量子计算方面的应用.本文综述了该体系在量子计算方面的研究进展,并介绍了我们在其中所做的两个贡献:一是实现了"魔幻强度光阱",克服了光阱中原子退相干的首要因素,将原子相干时间提高了百倍,使得相干时间与比特操作时间的比值高达105;二是利用异核原子共振频率的差异建立了低串扰的异核单原子体系,并利用里德伯阻塞效应首次实现了异核两原子的量子受控非门和量子纠缠,将量子计算的实验研究拓展至异核领域.最后,分析了中性单原子体系在量子模拟和量子计算方面进一步发展面临的挑战与瓶颈.     

纠缠态原子与相干光场作用的量子信息保真度

研究了初始处于纠缠态的双原子与相干光场的相互作用。结果表明,不同的失谐量和初始平均光子数使得系统、原子和光场的量子信息保真度发生改变。     

Production and guidance of pulsed atomic beams on chip

We demonstrated two experimental methods of producing and guiding pulsed atomic beams on chip. One is to trap atoms first in a U-type magneto-optical trap on the chip, then transfer them to the magnetic guide field and push them simultaneously by a continuous force from the power imbalance of the magneto-optical trap laser beams hence the pulsed cold atom beams are produced and move along the magnetic guide to the destination. The other is to trap atoms directly by a H-type magneto-optical trap, then push them to make them move along the magnetic guide field, thus high rate cold atom beams can be produced and guided on the chip.     

Doppler-free spectroscopy of rubidium atoms driven by a control laser

A scheme of Doppler-free spectroscopy is experimentally demonstrated with a co-propagating control laser locking to an atomic hyperfine transition, and the differential transmission of the probe and the reference laser is detected. Crossover resonances are eliminated by selecting the class of atoms with zero velocity in the direction of beam propagation. In addition, the sub-Doppler spectrum experiences optical gain compared to the conventional saturated-absorption spectrum as a result of optical pumping.     

里德堡钠原子抗磁谱的模型势计算

用B样条基组展开方法结合模型势计算了里德堡钠原子抗磁谱和相应的振子强度谱，径向和角向均采用高阶B样条基组．计算结果与已有的R-矩阵和多通道量子亏损理论相结合（R-matrix＋MODT）法及其他理论计算结果作了比较，几种理论结果在我们所研究的能区内符合得非常好，本文方法较R-matrix＋MQDT法简单，易于推广到交叉电磁场中里德堡原于的精确谱的计算中．     

LASER-CONTROLLED STATE EXCITATION AND QUANTUM COMPUTATION

Based on the dependence of the molecular excitation probabilities on the laser phases and amplitudes in the model of a three-mode laser interacting with a three-level molecule, we propose a scheme to implement quantum XOR logic gate and to construct quantum error prevention code.     

Ultranarrow bandwidth tunable atomic filter via quantum interference-induced polarization rotation in Rb vapor

We report the experimental demonstration of an ultranarrow bandwidth atomic filter by optically induced polarization rotation in multilevel electromagnetically induced transparency systems in hot Rb vapor. With a coupling intensity of 2.3 W/cm^2, the filter shows a peak transmission of 33.2% and a bandwidth of 10 MHz. By altering the coupling frequency, a broad tuning range of several Doppler linewidths of the D1 line transitions of STRb atoms can be obtained. The presented atomic filter has useful features of ultranarrow bandwidth, and the operating frequency can be tuned resonance with the atomic transition. Such narrowband tunable atomic filter can be used as an efficient noise rejection tool in classical and quantum optical applications.     

冷原子干涉仪及空间应用

原子干涉仪是利用原子物质波的特性而实现的干涉仪,冷原子具有很小的速度和速度分布以及良好的相干性,因而冷原子干涉仪具有很高的灵敏度.文章介绍了原子干涉仪的基本物理原理、国内外研究进展、原子干涉仪实现方案及其在精密测量和空间科学领域中的应用.     

Microwave coherent manipulation of cold atoms in optically induced fictitious magnetic traps on an atom chip

We propose a novel on-chip platform for controlling and manipulating cold atoms precisely and coherently. The scheme is achieved by producing optically induced fictitious magnetic traps(OFMTs) with 790 nm(for ~(87)Rb) circularly polarized laser beams and state-dependent potentials simultaneously for two internal atomic states with microwave coplanar waveguides. We carry out numerical calculations and simulations for controlled collisional interactions between OFMTs and addressable single atoms' manipulation on our designed hybrid atom chips. The results show that our proposed platform is feasible and flexible, which has wide applications including collisional dynamics investigation, entanglement generation,and scalable quantum gates implementation.