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arXiv 1012.5616quant-ph
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一个负Wigner函数的连续变量隐形传态

Continuous-variable teleportation of a negative Wigner function

Ladislav Mišta,, Radim Filip, Akira Furusawa

备注：
12 pages, 12 figures
发表信息：
Phys. Rev. A 82, 012322 (2010)
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摘要：

隐形传态是量子通信和量子计算的基本原理。我们解决了一般在非单位增益范围内的纯单光子态和混合衰减单光子态的连续变量（无条件和有条件）隐形传态问题。我们的品质因数是维格纳函数的最大负值，证明了远距传送态的高度非经典特征。我们发现，对于任意的弱压缩态，单光子态的Wigner函数为负时，可以{ \em无条件}隐形传态。相比之下，对于衰减单光子态，为了成功地传送其维格纳函数的负性，必须超过严格的阈值压缩。{ \em条件}隐形传态允许以成功率为代价，在任意低的压缩下接近单光子的完美传输。另一方面，对于衰减单光子，条件隐形传态不能克服无条件隐形传态的压缩阈值，只有当压缩同时增加时，条件隐形传态才接近于输入态的负态。然而，一旦超过阈值压缩，条件隐形传态仍然明显优于无条件隐形传态。讨论了连续变量量子通信和量子计算的主要结果。

英文摘要：

Teleportation is a basic primitive for quantum communication and quantum computing. We address the problem of continuous-variable (unconditional and conditional) teleportation of a pure single-photon state and a mixed attenuated single-photon state generally in a nonunity gain regime. Our figure of merit is the maximum of negativity of the Wigner function that witnesses highly non-classical feature of the teleported state. We find that negativity of the Wigner function of the single-photon state can be {\em unconditionally} teleported for arbitrarily weak squeezed state used to create the entangled state shared in the teleportation. In contrast, for the attenuated single-photon state there is a strict threshold squeezing one has to surpass in order to successfully teleport the negativity of its Wigner function. The {\em conditional} teleportation allows to approach perfect transmission of the single photon for an arbitrarily low squeezing at a cost of a success rate. On the other hand, for the attenuated single photon conditional teleportation cannot overcome the squeezing threshold of the unconditional teleportation and it approaches negativity of the input state only if the squeezing simultaneously increases. However, as soon as the threshold squeezing is surpassed the conditional teleportation still pronouncedly outperforms the unconditional one. The main consequences for quantum communication and quantum computing with continuous variables are discussed.

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