量子纠缠态制备、操纵的实验研究

doi:10.7523/j.issn.2095-6134.2009.4.020

摘要/Abstract

摘要：

量子纠缠是量子信息学中最重要也是最为奇特的一个课题.在量子信息学中,量子信息的处理离不开量子态及其操纵,而量子纠缠态毫无疑问是各种各样的量子态中最重要的一种. 利用光子纠缠态开展了以下实验研究:(1)利用连续波激光束泵浦非线性晶体的自发参量下转换过程,制备出了双光子偏振纠缠态,具有较高亮度和纠缠度,并具有纠缠度可调谐的特点. 利用这种纠缠源,制备了量子信息学中一种重要的混合态——Werner态,采用的方案使得Werner态中纠缠的成分是可控制的.(2)利用线性光学元件以及路径比特概念的引入,在实验上用单光子实现了Buek-Hillery普适克隆机,实验结果表明,对任意的输入纯态,此克隆机输出的2份拷贝与初始态均达到5/6的保真度,与理论计算一致.(3)在实验上利用自发参量下转换系统制备的双光子偏振最大纠缠态及非最大纠缠态进行了CHSH不等式的检验,验证了对于2比特纠缠纯态,"纠缠"等价于"Bell不等式违背"这一结论.(4)除了局域隐变量理论之外,还有一种主要的隐变量理论——环境无关的隐变量理论(NCHV),关于这种隐变量,类似于Bell不等式,有一个Kochen-Specker理论,其主要内容是证明NCHV和量子力学的矛盾. 完成了一个用单光子实现的检验Kochen-Spcker理论的实验,实验结果证明了NCHV是不存在的.

关键词: 纠缠光子, 自发参量下转换, 量子纠缠操纵

Abstract:

This paper presents our experimental work on preparing and manipulating quantum entangled states in optical quantum information processing systems. The main contents are: (1) Using continuous wave(CW) laser beam to pump nonlinear crystals we successfully prepared two-photon polarization entangled states with high brightness and entanglement degree, and it is tunable in entanglement degree and we use this source to produce one kind of important mixed states——Werner states with tunable entanglement fraction in it. (2) We realized the 1→2 qubits Buek-Hillery cloning machine with linear optical devices and showed that the fidelities between the two output qubits and the original qubit are both 5/6 for arbitrary input pure states. (3) We presented a method to test the maximal violation of the CHSH inequality for non-maximally entangled pure states and experimentally realized it with our entangled state source. (4) We perform an all-or-nothing-type Kochen-Specker experiment to verify whether non-contextual hidden variables (NCHV) or quantum mechanics is right. The results strongly agree with quantum mechanics.

Key words: entangled photons, spontaneous parametric down conversion (SPDC), quantum entanglement manipulation

中图分类号:

O438

黄运锋, 郭光灿. 量子纠缠态制备、操纵的实验研究[J]. 中国科学院大学学报, 2009, 26(4): 569-576.

HUANG Yun-Feng, GUO Guang-Can. Experimental preparation and manipulation of quantum entangled states[J]. , 2009, 26(4): 569-576.

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