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1.
We experimentally demonstrate continuous-variable quantum teleportation beyond the no-cloning limit. We teleport a coherent state and achieve the fidelity of 0.70 +/- 0.02 that surpasses the no-cloning limit of 2/3. Surpassing the limit is necessary to transfer the nonclassicality of an input quantum state. By using our high-fidelity teleporter, we demonstrate entanglement swapping, namely, teleportation of quantum entanglement, as an example of transfer of nonclassicality. 相似文献
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We experimentally demonstrate quantum teleportation for continuous variables by using squeezed-state entanglement. A fidelity expression for a real experimental system is presented, where all the imperfection factors are considered, including losses and phase fluctuations. The measured fidelity for input coherent states is 0.62 and the prospective result with our measured entanglement and efficiencies is 0.69. We will show the details of the quantum teleportation for continuous variable and discuss the problems for further improvement in this experiment. 相似文献
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Y. Zhou G.-F. Zhang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):227-231
We study quantum teleportation via a two-qubit Heisenberg
XXZ chain under an inhomogeneous magnetic field. We first consider entanglement
teleportation, and then focus on the teleportation fidelity under different
conditions. The effects of anisotropy and the magnetic field, both uniform
and inhomogeneous, are discussed. We also find that, though entanglement
teleportation does require an entangled quantum channel, a nonzero critical
value of minimum entanglement is not always necessary. 相似文献
5.
GUO Jin-Liang NIE Jing SONG He-Shan 《理论物理通讯》2008,49(6):1435-1438
We consider a two-qubit Heisenberg XXZ chain as a resource for quantum teleportation via the standard teleportation protocol To. The effects of anisotropic on teleportation fidelity and entanglement are studied in detail. We find anisotropic not only improves the criticM temperature Tc and criticM magnetic field Bc, beyond which quantum teleportation is inferior to classicM communication protocol, but also enhances the fidelity for fixed magnetic field B and temperature T. For entanglement teleportation, the effects of magnetic field on average fidelity and output entanglement are studied. 相似文献
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We present a formalism to derive entanglement criteria beyond the Gaussian regime that can be readily tested by only homodyne detection. The measured observable is the Einstein-Podolsky-Rosen (EPR) correlation. Its arbitrary functional form enables us to detect non-Gaussian entanglement even when an entanglement test based on second-order moments fails. We illustrate the power of our experimentally friendly criteria for a broad class of non-Gaussian states under realistic conditions. We also show rigorously that quantum teleportation for continuous variables employs a specific functional form of EPR correlation. 相似文献
9.
We investigate experiments of continuous-variable quantum information processing based on the teleportation scheme. Quantum
teleportation, which is realized by a two-mode squeezed vacuum state and measurement-and-feedforward, is considered as an
elementary quantum circuit as well as quantum communication. By modifying ancilla states or measurement-and-feedforwards,
we can realize various quantum circuits which suffice for universal quantum computation. In order to realize the teleportation-based
computation we improve the level of squeezing, and fidelity of teleportation. With a high-fidelity teleporter we demonstrate
some advanced teleportation experiments, i.e., teleportation of a squeezed state and sequential teleportation of a coherent
state. Moreover, as an example of the teleportation-based computation, we build a QND interaction gate which is a continuous-variable
analog of a CNOT gate. A QND interaction gate is constructed only with ancillary squeezed vacuum states and measurement-and-feedforwards.
We also create continuous-variable four mode cluster type entanglement for further application, namely, one-way quantum computation. 相似文献
10.
We consider the standard quantum teleportation protocol where a general bipartite state is used as entanglement resource. We use the entanglement fidelity to describe how well the standard quantum teleportation channel transmits quantum entanglement and give a simple expression for the entanglement fidelity when it is averaged on all input states. 相似文献
11.
We examine entanglement teleportation,characterized by average fidelity,of two-qubit XY Z spin chain under different nonuniform magnetic field.The entanglement teleportation and the fidelity of entanglement teleportation are investigated separately.We show explicitly that the fidelity of entanglement teleportation can be enhanced by changing the direction of the magnetic field.This means that we can always get optimal fidelity by choosing the directions of magnetic field in the process of quantum teleportation.Moreover,the results show that in some cases the ferromagnetic chain also is a qualified candidate in the process of teleportation protocol. 相似文献
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Hai-Lin Huang 《International Journal of Theoretical Physics》2011,50(1):70-79
The quantum teleportation via a two-qubit Ising Heisenberg chain in the presence of an external magnetic field with an arbitrary
direction are investigated. The effect of the orientation of an external magnetic field on the entanglement teleportation
has been analyzed numerically. It is found that the teleported thermal concurrence and average fidelity can be maximized by
rotating the magnetic field (with fixed magnitude) to an optimal direction. The ferromagnetic channel is not suitable to teleportation.
A minimal entanglement of the thermal state is needed to realize the entanglement teleportation for antiferromagnetic channel.
It is also found that the entanglement of the channel cannot completely reflect the teleported concurrence and average fidelity.
There exist double-value phenomena between them. 相似文献
14.
Transfer of entanglement and information is studied for quantum teleportation of an unknown entangled state through noisy quantum channels. We find that the quantum entanglement of the unknown state can be lost during the teleportation even when the channel is quantum correlated. We introduce a fundamental parameter of correlation information which dissipates linearly during the teleportation through the noisy channel. Analyzing the transfer of correlation information, we show that the purity of the initial state is important in determining the entanglement of the replica state. 相似文献
15.
提出利用单个三粒子最大Greenberger-Horne-Zeilinger (GHZ)态或两个Einstein-Podolsky-Rosen (EPR)态作为量子信道确定性隐形传送任意三粒子GHZ态的两个方案,并将方案推广至隐形传送任意n(n≥4)粒子GHZ态的情况.讨论了量子信道受噪声影响时隐形传态的保真度.研究发现,当作为量子信道的单个三粒子最大GHZ态受到噪声影响时,隐形传态的保真度仅与量子信道的纠缠度有关,而当作为量子信道的两个EPR态受到噪声影响时,隐形传态的保真度不仅与量子信道的纠缠度有关,还与待传送态的纠缠度有关.所提出的方案具有节省量子信道纠缠资源的特点.
关键词:
隐形传态
三粒子Greenberger-Horne-Zeilinger态
量子逻辑门
保真度 相似文献
16.
Thermal entanglement and teleportation of a thermally mixed entangled state of a Heisenberg chain through a Werner state
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The thermal entanglement and teleportation of a thermally mixed entangled state of a two-qubit Heisenberg XXX chain under the Dzyaloshinski Moriya (DM) anisotropic antisymmetric interaction through a noisy quantum channel given by a Werner state is investigated. The dependences of the thermal entanglement of the teleported state on the DM coupling constant, the temperature and the entanglement of tbe noisy quantum channel are studied }n detail for both the ferromagnetic and the antiferromagnetic cases. The result shows that a minimum entanglement of the noisy quantum channel must be provided in order to realize the entanglement teleportation. The values of fidelity of the teleported state are also studied for these two cases. It is found that under certain conditions, we can transfer an initial state with a better fidelity than that for any classical communication protocol. 相似文献
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Li-Guo Qin Li-Jun Tian Guo-Hong Yang 《International Journal of Theoretical Physics》2013,52(12):4313-4322
We study the thermal entanglement and teleportation using quantum dot as the quantum channel. We firstly investigate the evolution of entanglement in the vertical quantum dot, then focus on the effects of the important parameters of the system on the teleported fidelity under different conditions. We obtain the critical temperature of suddenly dead entanglement. Based on Bell measurements in two subspaces, the isotropy and anisotropy subspaces, we can find that the anisotropy measurements always overmatch the isotropy ones. Moreover, we obtain the high-fidelity teleportation for quantum dot as quantum channel when the parameters are adjusted. The possible applications of quantum dot are expected in quantum teleportation 相似文献
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在振幅阻尼信道上进行量子隐形传态的过程中, 量子Bell纠缠态将发生退相干, 导致隐形传态质量下降甚至通信失败. 为克服该影响, 本文提出了一种Bell纠缠态补偿方法. 在估计振幅阻尼信道参数的基础上, 将对纠缠态的补偿分为纠缠退相干发生之前的预补偿以及 经历量子振幅阻尼信道之后的匹配补偿两部分. 前者在纠缠源处进行, 后者在两个量子通信 用户处进行, 预补偿及匹配补偿参数与信道特性参数相关. 纠缠补偿完成后, 再进行隐形传态. 理论推导与性能分析结果表明, 相比于不进行纠缠补偿及仅在发生退相干之后进行的纠缠补偿, 本方法能够获得更高的隐形传态保真度, 适当调整补偿参数, 可使保真度接近于1, 对克服纠缠 退相干带来的隐形传态质量下降问题具有一定的意义. 相似文献
19.
P. van Loock 《Fortschritte der Physik》2002,50(12):1177-1372
Many quantum communication schemes rely on the resource of entanglement. For example, quantum teleportation is the transfer of arbitrary quantum states through a classical communication channel using shared entanglement. Entanglement, however, is in general not easy to produce on demand. The bottom line of this work is that a particular kind of entanglement, namely that based on continuous quantum variables, can be created relatively easily. Only squeezers and beam splitters are required to entangle arbitrarily many electromagnetic modes. Similarly, other relevant operations in quantum communication protocols become feasible in the continuous‐variable setting. For instance, measurements in the maximally entangled basis of arbitrarily many modes can be accomplished via linear optics and efficient homodyne detections. In the first two chapters, some basics of quantum optics and quantum information theory are presented. These results are then needed in Chapter III, where we characterize continuous‐variable entanglement and show how to make it. The members of a family of multi‐mode states are found to be truly multi‐party entangled with respect to all their modes. These states also violate multi‐party inequalities imposed by local realism, as we demonstrate for some members of the family. Further, we discuss how to measure and verify multi‐party continuous‐variable entanglement. Various quantum communication protocols based on the continuous‐variable entangled states are discussed and developed in Chapter IV. These include the teleportation of entanglement (entanglement swapping) as a test for genuine quantum teleportation. It is shown how to optimize the performance of continuous‐variable entanglement swapping. We highlight the similarities and differences between continuous‐variable entanglement swapping and entanglement swapping with discrete variables. Chapter IV also contains a few remarks on quantum dense coding, quantum error correction, and entanglement distillation with continuous variables, and in addition a review of quantum cryptographic schemes based on continuous variables. Finally, in Chapter V, we consider a multi‐party generalization of quantum teleportation. This so‐called telecloning means that arbitrary quantum states are transferred not only to a single receiver, but to several. However, due to the quantum mechanical no‐cloning theorem, arbitrary quantum states cannot be perfectly copied. We present a protocol that enables telecloning of arbitrary coherent states with the optimal quality allowed by quantum theory. The entangled states needed in this scheme are again producible with squeezed light and beam splitters. Although the telecloning scheme may also be used for "local'' cloning of coherent states, we show that cloning coherent states locally can be achieved in an optimal fashion without entanglement. It only requires a phase‐insensitive amplifier and beam splitters. 相似文献
20.
Faithful long-distance quantum teleportation necessitates prior
entanglement distribution between two communicated locations. The
particle carrying on the unknown quantum information is then
combined with one particle of the entangled states for Bell-state
measurements, which leads to a transfer of the original quantum
information onto the other particle of the entangled states. However
in most of the implemented teleportation experiments nowadays, the
Bell-state measurements are performed even before successful
distribution of entanglement. This leads to an instant collapse of
the quantum state for the transmitted particle, which is actually a
single-particle transmission thereafter. Thus the true distance for
quantum teleportation is, in fact, only in a level of meters. In the
present experiment we design a novel scheme which has overcome this
limit by utilizing fiber as quantum memory. A complete quantum
teleportation is achieved upon successful entanglement distribution
over 967 meters in public free space. Active feed-forward control
techniques are developed for real-time transfer of quantum
information. The overall experimental fidelities for teleported
states are better than 89.6%, which signify high-quality
teleportation. 相似文献