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911.
A scheme, based on the two two-level atoms resonantly
driven by the classical field separately trapped in two cavities
coupled by an optical fibre, for the implementation of remote
two-qubit gates is investigated. It is found that the quantum
controlled-phase and swap gates can be achieved with the assistance
of the classical field when there are detunings of the coupling quantum
fields. Moreover, the influence of the dissipation of the cavities
and the optical fibre is analysed while the spontaneous emission of
the atoms can be effectively suppressed by introducing Λ-type atoms. 相似文献
912.
913.
We put forward an optimal entanglement concentration protocol(ECP) for recovering an arbitrary less-entangled multi-photon Greenberger–Horne–Zeilinger(GHZ) state into the maximally entangled GHZ state based on the photonic Faraday rotation in low-quality(Q) cavity. In the ECP, only one pair of less-entangled multi-photon GHZ state and one auxiliary photon are required, and the concentration task can be realized by local operations. Moreover, our ECP can be used repeatedly to further concentrate the discarded items of conventional ECPs, which can increase its success probability largely. Under the practical imperfect detection condition, our protocol can still work with relatively high success probability. This ECP has application potential in current and future quantum communication. 相似文献
914.
Multi-copy entanglement purification with practical spontaneous parametric down conversion sources
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Entanglement purification is to distill the high quality entanglement from the low quality entanglement with local operations and classical communications. It is one of the key technologies in long-distance quantum communication. We discuss an entanglement purification protocol(EPP) with spontaneous parametric down conversion(SPDC) sources, in contrast to previous EPP with multi-copy mixed states, which requires ideal entanglement sources. We show that the SPDC source is not an obstacle for purification, but can benefit the fidelity of the purified mixed state. This EPP works for linear optics and is feasible in current experiment technology. 相似文献
915.
Christopher J. Stein 《Molecular physics》2017,115(17-18):2110-2119
ABSTRACTOne of the most critical tasks at the very beginning of a quantum chemical investigation is the choice of either a multi- or single-configurational method. Naturally, many proposals exist to define a suitable diagnostic of the multi-configurational character for various types of wave functions in order to assist this crucial decision. Here, we present a new orbital-entanglement-based multi-configurational diagnostic termed Zs(1). The correspondence of orbital entanglement and static (or non-dynamic) electron correlation permits the definition of such a diagnostic. We chose our diagnostic to meet important requirements such as well-defined limits for pure single-configurational and multi-configurational wave functions. The Zs(1) diagnostic can be evaluated from a partially converged, but qualitatively correct, and therefore inexpensive density matrix renormalisation group wave function as in our recently presented automated active orbital selection protocol. Its robustness and the fact that it can be evaluated at low cost make this diagnostic a practical tool for routine applications. 相似文献
916.
闫丽 《原子与分子物理学报》2017,34(4):716-721
本文将两个二能级原子注入一个腔中,用共生纠缠的方法来度量两原子之间的纠缠并推出它们之间的量子失协,还给出了原子与环境之间的共生纠缠与量子失协的计算公式,讨论了原子自发衰变率的变化对量子纠缠及失协的影响,及不同的初始状态情况下,纠缠及失协随原子距离的演化情况.结果表明:原子自发衰变率减小,原子与环境之间的量子纠缠及失协增加;选择不同的初态,可以控制原子间出现纠缠死亡的现象或量子失协为零的状态. 相似文献
917.
提出了一种基于Greenberger-Horne-Zeilinger(GHZ)纠缠态进行纯EPR对双向隐形传态的方案.通过使用纠缠交换技术,通信双方Alice和Bob共享两对三粒子GHZ纠缠态来构建量子信道.方案中通过使用受控非门操作,单量子位测量以及适当的幺正操作,通信双方可以同时发送一个纯EPR对给对方.故相比仅可以传送单一量子态的方案更经济. 相似文献
918.
根据Milburn理论,研究了考虑内禀退相干情况下,三粒子XXZ海森堡系统在DzyaloshinskiiMoriya(DM)相互作用和各向异性参数的影响下的量子纠缠演化特性.分析了不同DM相互作用和內禀退相干因子等参数对量子对纠缠度的影响.研究表明:系统的对纠缠度与各向异性参数Δ无关,但DM相互作用和內禀退相干都对系统的对纠缠都有明显的影响.当无DM相互作用只存在內禀退相干时,系统的三对对纠缠度各不相同;引入DM相互作用后,系统的对纠缠度的稳定值将改变;选择合适的DM相互作用参数时,系统的对纠缠度随时间做震荡,随着时间的延长,震荡减弱至一个非零的稳定值;并且系统的对纠缠随內禀退相干增大,震荡幅度变小,震荡时间变短.因此,在內禀退相干存在时,合适的DM相互作用参数可以有效的控制对纠缠. 相似文献
919.
920.
A hybrid optomechanical system which is composed of an atomic ensemble and a standard optomechanical cavity driven by a periodically modulated external laser field is investigated. Based on the simple periodic modulation forms of the driving amplitude and effective optomechanical coupling, respectively, the atom‐mirror entanglement is discussed in detail. It is found that the maximum of the entanglement in the unresolved‐sideband regime can be further enhanced compared with the non‐modulation regime. On the other hand, we find that the introduction of the atomic ensemble permits the mechanical squeezing induced by the periodic amplitude modulation can be successfully generated even in the unresolved‐sideband regime. Due to the self‐cooling mechanism constructed by the atomic ensemble, the mechanical squeezing scheme no longer requires the extra precooling technologies. 相似文献