螺旋光纤系统中非绝热条件几何相移  

The nonadiabatic conditional geometric phase shift in a coiled fiber system

作　　者：沈建其[1] 庄飞[2] 

机构地区：[1]浙江大学光及电磁波研究中心,瑞典皇家工学院-浙江大学联合光子学研究中心,杭州310027 [2]杭州师范学院物理系,杭州310012

出　　处：《物理学报》2005年第3期1048-1052,共5页Acta Physica Sinica

基　　金：浙江省教育厅教研配套项目 (批准号 :2 0 0 2ZSMN0 0 2 );浙江省自然科学基金 (批准号 :Y40 43 5 5 )资助的课题 .;沈建其受瑞典Wenner_Gren基金会资助 .~~

摘　　要：由于绝热条件几何相位量子逻辑门存在非绝热差错与退相干差错这一冲突 ,因此在拓扑量子计算中需要设计非绝热条件几何相门 ,以克服这一不足 .证明螺旋光纤系统内光子有效哈密顿量恰好是一个Wang Matsumoto型哈密顿量 ,因此螺旋光纤系统能自动产生非绝热条件几何相移 .同时还证明在螺旋光纤方案中 ,由极化光子与螺旋光纤相互作用哈密顿量所导致的动力学相位为零 (这正是拓扑量子计算所要求的 ) ,以及在螺旋光纤系统中可以通过控制极化光子初始波矢 ,从而较容易获得条件初始态 .总之 ,螺旋光纤系统方案能自动满足Wang与Matsumoto的核磁共振方案中为实现非绝热条件几何相移所提出的全部条件与要求 .The nonadiabatic conditional geometric phase gate is required in the topological quantum computation in order to overcome the conflict between the requirement of adiabatic condition(to avoid the severe distortion from the nonadiabaticity to the results) and the removal of decoherence effects. It was demonstrated that the effective Hamiltonian that describes the propagation of photon fields inside the coiled fiber is just the Wang-Matsumoto type of Hamiltonian. Thus, the coiled fiber system will automatically generate the nonadiabatic conditional geometric phase shift. In addition, it was shown that the dynamical phase (resulting from the effective Hamiltonian) acquired by the polarized photons vanishes, and the conditional initial state can be easily prepared only by controlling the initial wave vector of photons. In a word, the coiled fiber system can automatically satisfy the requirements and conditions, which were proposed by Wang and Matsumoto in order to create the nonadiabatic conditional geometric phase shift in their NMR scheme.

关 键 词：哈密顿量 光子 量子计算 几何相位 相移 证明 拓扑 条件 要求 螺旋 

分 类 号：TN256[电子电信—物理电子学]