去北海游泳


这些天我和堂弟,表妹在堂姐家玩。堂姐在南宁工作,昨天由她的男朋友开车带我们去北海银滩游泳。

从南宁走高速路到北海要两个多小时,我们早上10点出发,到那里时已经快下午1点了。找了家饭馆解决了午饭,吃的全是海鲜。太阳很大,我们先去北海 海洋公园观赏海底生物。各种色彩绚丽的海洋鱼,重200公斤的大海龟,可爱的海豹,凶猛的食肉鱼,精彩的人鲨共舞,我头一次来海洋公园,确实有眼花缭乱的 感觉。

从海洋公园里出来已经4点多了,我们驱车前往银滩。北海的银滩很有名,据说是国家4A的风景区。下车花了1元找了个更衣室换上游泳衣,我们踏上海 滩。真是神奇,这么大的一片海滩居然全是银色的。我忍不住用手捧起一捧沙子,发现沙粒极细,极均匀,很纯净,怪不得看上去发银色的光芒呢!

太阳已经偏西,天上有几片白云,海风轻拂,海浪很轻轻的击打着沙滩。我忍不住要下水,堂姐说这么好的景色,还是先照几张相吧。于是我们几个人摆了好 几个姿势照了几张相。我戴上游泳镜,慢慢的向大海走去。海水是绿色的,让人有点失望。水渐渐深了,我感觉到了海浪的力量和海水的浮力。我只前进到齐胸深的 地方就停止了,然后平行于海岸游。海水比较清,当海水渗入我的口中时,我才感觉到苦涩的滋味,发现在海水中游泳确实不同于游泳池中游,一定要很小心,不能 被海水呛到,否则会很难受的。

海中人比较多,但海滩很大,所以人的密度并不大,我可以畅快的游泳。蛙泳,仰泳,自由泳,我尝试着各种泳姿,还和堂弟竞赛游泳。当我们离开沙滩时发现海水已经涨到我们的遮阳伞旁边了,原来我们来的时候正值涨潮,海水上涨的速度非常快。

过两天我会去桂林,希望能看到更美的风景。

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Adiabatic Quantum algorithms and QC in DFS via measurement


Here I list two papers recently posted on the arxiv which I thought interesting or important.

Adiabatic quantum algorithms and quantum phase transitions in quant-ph/0608017, Ralf Schützhold, Gernot Schaller from Dresden University of Technology reveal the similarity between adiabatic quantum algorithms and quantum phase transitions. They found that the Grover algorithm was corresponding to the first order of quantum phase transitions. They found that the second or higher order transitions were much better than first order one. With this insight, they proposed a novel adiabatic quantum algorithm for the solution of 3-satisfiability (3-SAT) problems, which is much faster than the Grover algorithm, possibly even with an exponential speed-up.

Universal quantum computation in deocoherence-free subspace with neutral atoms in quant-ph/0607175, P. Xue and Y.F. Xiao from IQOQI and USTC proposed a scheme that realizing universal quantum computation between via measurement in deterministic way. They show how to implement cavity-assisted interaction between neutral atoms and coherent optical pulses. The quantum gates act on decoherence-free subspace. Therefore the dominant source of decoherence — dephasing is highly depressed. The homodyne detection of the coherent state directly measure the relative phase of the signal state, so the photon losses only decrease the fidelity but not lead to a failure of the measurement.