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arXiv 1402.4895quant-ph
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利用混合技术实现光子量子比特的确定性量子隐形传态

Deterministic quantum teleportation of photonic quantum bits by a hybrid technique

Shuntaro Takeda, Takahiro Mizuta, Maria Fuwa, Peter van Loock, Akira Furusawa

摘要:

量子隐形传态允许将任意的、原则上未知的量子态从发送者传送到空间上遥远的接收者,接收者共享纠缠态并且可以经典地通信。它是许多复杂的量子通信和计算协议的本质。为了在这些方案中实现飞行量子比特,光子是最佳选择,然而,由于实验效率低下和限制,隐形传态光子量子比特受到限制。主要缺点是线性光学贝尔测量的根本概率性质,以及当探测器无法解析光子数时需要破坏传送的量子位或衰减输入的量子位。在这里,我们实验上实现了光子量子比特的完全确定的、无条件的量子隐形传态。关键要素是利用“混合”技术:连续变量(CV)隐形传态的离散变量,光子量子比特。通过优化调谐接收器的前馈增益,CV传送器充当纯损耗通道,而基于单光子的输入双轨编码量子位表示针对振幅阻尼的量子错误检测码,因此对于大多数传送事件保持完全完整。这使得即使在不完美的CV纠缠态下也可以进行忠实的量子比特传输:对于四个不同的量子比特,总的传输概率范围从0.79到0.82,所有这些都超过了经典的隐形传态极限。此外,即使在相对较低的纠缠水平下,量子比特的传送也比以前的实验更有效,尽管是后选择性的(只考虑量子比特子空间),保真度与以前报道的值相当。

英文摘要:

Quantum teleportation allows for the transfer of arbitrary, in principle, unknown quantum states from a sender to a spatially distant receiver, who share an entangled state and can communicate classically. It is the essence of many sophisticated protocols for quantum communication and computation. In order to realize flying qubits in these schemes, photons are an optimal choice, however, teleporting a photonic qubit has been limited due to experimental inefficiencies and restrictions. Major disadvantages have been the fundamentally probabilistic nature of linear-optics Bell measurements as well as the need for either destroying the teleported qubit or attenuating the input qubit when the detectors do not resolve photon numbers. Here we experimentally realize fully deterministic, unconditional quantum teleportation of photonic qubits. The key element is to make use of a "hybrid" technique: continuous-variable (CV) teleportation of a discrete-variable, photonic qubit. By optimally tuning the receiver's feedforward gain, the CV teleporter acts as a pure loss channel, while the input dual-rail encoded qubit, based on a single photon, represents a quantum error detection code against amplitude damping and hence remains completely intact for most teleportation events. This allows for a faithful qubit transfer even with imperfect CV entangled states: the overall transfer fidelities range from 0.79 to 0.82 for four distinct qubits, all of them exceeding the classical limit of teleportation. Furthermore, even for a relatively low level of the entanglement, qubits are teleported much more efficiently than in previous experiments, albeit post-selectively (taking into account only the qubit subspaces), with a fidelity comparable to the previously reported values.

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