Controlled dense coding for continuous variables using three-particle entangled states
Controlled dense coding for continuous variables using three-particle entangled states
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DOI：
10.1103/physreva.66.032318
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发表时间：
2002-09
影响因子：
2.9
通讯作者：
Jing Zhang;C. Xie;K. Peng
中科院分区：
文献类型：
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作者：
Jing Zhang;C. Xie;K. Peng
在量子信息理论和实验研究的发展过程中，量子隐形传态（将未知量子态从发送者到远程接收者@1#）和密集编码（发送者发送到接收者的单个比特可以成功携带两个比特的经典信息@2#）引起了人们的广泛兴趣。非局域量子纠缠在量子信息处理中起着决定性的作用。自EinsteinPodolsky-Rosen ~EPR！利用压缩光场和分束器可以有效地产生纠缠态，例如，双模压缩真空态产生的纠缠EPR对已经成功地用于无条件量子隐形传态@3#.随后，从理论上提出了实现连续变量高效密集编码的方案，其中利用双模压缩态纠缠实现了@4-6#信号的无条件传输。用非简并光学参量放大器NOPA实验产生了明亮的EPR光束。@7#和基于明亮EPR光束的连续变量的密集编码已在@8#中得到初步验证。Loock和Braunstein给出了多个独立压缩态的叠加可以产生连续变量的多体纠缠，并提出了利用纠缠三模态@9#实现量子隐形传态的方案。这个方案中的保真度取决于第三个粒子的测量。最近提出了离散变量的受控密集编码，使用Greenberger-Horne-Zeilinger态~GHZ！@10#。受稠密编码与量子隐形传态的相似性和差异性的启发，本文研究了利用三重纠缠态实现稠密编码的方法。结果表明，当采用三重纠缠态时，密集编码的信息传输能力受第三粒子的测量控制。通过对非简并光参量放大器的研究，提出了一种简单的、实验上可实现的、可控制的连续变量密集编码方案。由于采用
In the development of theoretical and experimental studies of quantum information, the quantum teleportation that is the disembodied transport of an unknown quantum state from a sender to a remote receiver @1# and the dense coding in which the single bit sent from a sender to a receiver can successfully carry two bits of classical information @2#, have attracted extensive interests. The nonlocal quantum entanglement plays a determinant role in the quantum information processing. Towards possible applications in quantum communication, both theoretical and experimental investigations increasingly focus on quantum states of continuous variables in an infinite-dimensional Hilbert space, since the EinsteinPodolsky-Rosen ~EPR! entangled state can be efficiently generated using squeezed light and beam splitters, for instance, the entangled EPR pairs resulting from two-mode squeezed vacuum state have been successfully employed in demonstrating unconditional quantum teleportation @3#. Later, the schemes realizing highly efficient dense coding for continuous variables are theoretically proposed, in which the two-mode squeezed-state entanglement is utilized to achieve unconditional signal transmission @4–6#. The bright EPR beams have been experimentally produced with a nondegenerate optical parametric amplifier ~NOPA! @7# and the dense coding for continuous variables based on bright EPR beam has been demonstrated initially @8#. Loock and Braunstein have given that the superposition of more than independently squeezed states can yield multipartite entanglement for continuous variables and presented the scheme of quantum teleportation using entangled three-mode state @9#. The fidelity in this scheme depends on the measurement of the third particle. Controlled dense coding for discrete variables was proposed recently using the Greenberger-Horne-Zeilinger state ~GHZ! @10#. Inspired by the similarity and difference between dense coding and quantum teleportation, in this paper we study dense coding using the tripartite entangled state. It is shown that when using the tripartite entangled state, the information transmission capacity of dense coding is controlled by the measurement of the third particle. We introduce a simple, experimentally realizable, controlled dense coding protocol for continuous variables by exploring nondegenerate optical parametric amplifier. Due to adopting the