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1、龙源期刊网 http:/囚禁离子多体w类纠缠态的简单制备方案作者：汪新文 唐世清来源：湖南师范大学学报 自然科学版2013年第03期摘 要 提出一种囚禁离子多体 W 类纠缠态的简单制备方案 .在该方案中， N 个离子被一束红 边带激光同时照射，从而可以实现 N 体对称 W 态或 N+1 体反对称 W 态的一步产生 .原则上， 粒子数 N 可以任意大 .另外，离子数越大，制备目标纠缠态所需要的时间就越短 .关键词 W 态；囚禁离子；一步产生Quantum entanglement is a consequence of quantumstate superposition principle a
2、pplied to composite quantum systems. It not only provides possibilities to test the foundations of quantum physics ， but also lies at the heart of the growing field of quantum information science1. Compared with bipartite entangled states ， multipartite entangled states would exhibit clearer nonclas
3、sical effects and are more useful for quantum applications23. Thus characterizing and preparing multipartite entangled states have been attracting much attention. However ， preparation of multipartite entangled states is an experimental challenge ， because of the technical difficulty of manipulating
4、 individual particles. So far ， tripartite GreenbergerHorneZeilinger （ GHZ ） state in cavity QED4 ， 10photon GHZ state5 ， 6photon cluster state6 ， 3photon W state7 ， and 14ion GHZ state8 have been observed. Wtype entangled state is a special type of multipartite entangled state9， and has widespread
5、applications in quantum information processing （ see， e.g.， Refs. 1014 ） . Thus， generation of multiparticle Wtype states has been paid much attention.湖南师范大学自然科学学报 第 36卷第 3 期汪新文等：囚禁离子多体 W 类纠缠态的简单制备方案 Not long before ， the Innsbruck group has experimentally prepared 40Ca+ionic 8qubit W state15 ， with
6、 S1/2 （ mj=1/2 ） acting as the lower level and D5/2 （ mj=-1/2 ） acting as the upper level. In the experiment ， they individually derived each of the ions with sequential blue sideband pulses ， and created a W state step by step with one motional quantum as memory. In this paper ， we propose an alter
7、native scheme to generate multipartite entanglement of the W type in the iontrap system ， which can be regarded as an improvement on that of Ref.15. In the scheme ， an Nion W state can be created in one step by driving simultaneously the ions with one red sideband laser beam. Moreover ， the larger t
8、he number of ions N is ， the less time it will take to prepare the desired state. Thus our scheme is much faster and simpler than that of Ref.15 ， which is very important in view of decoherence.We consider that N identical ions （ for example ， 40Ca+ ions ） are confined in a linear Paul trap. Each of them has the ground state gand the excited state e .We simultaneously drive the ions using a red sideband laser beam with frequency of - v, where 0is the frequency of electronic
