Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0020, Japan.
The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
Sci Rep. 2017 Mar 31;7:45353. doi: 10.1038/srep45353.
Quantum information science addresses how the processing and transmission of information are affected by uniquely quantum mechanical phenomena. Combination of two-qubit gates has been used to realize quantum circuits, however, scalability is becoming a critical problem. The use of three-qubit gates may simplify the structure of quantum circuits dramatically. Among them, the controlled-SWAP (Fredkin) gates are essential since they can be directly applied to important protocols, e.g., error correction, fingerprinting, and optimal cloning. Here we report a realization of the Fredkin gate for photonic qubits. We achieve a fidelity of 0.85 in the computational basis and an output state fidelity of 0.81 for a 3-photon Greenberger-Horne-Zeilinger state. The estimated process fidelity of 0.77 indicates that our Fredkin gate can be applied to various quantum tasks.
量子信息科学研究信息的处理和传输如何受到独特的量子力学现象的影响。双量子比特门的组合已被用于实现量子电路，然而，可扩展性正成为一个关键问题。三量子比特门的使用可能会极大地简化量子电路的结构。在这些门中，受控-SWAP（Fredkin）门是必不可少的，因为它们可以直接应用于重要的协议，例如错误校正、指纹识别和最优克隆。在这里，我们报告了一种用于光子量子比特的 Fredkin 门的实现。我们在计算基中实现了 0.85 的保真度，对于 3 光子 Greenberger-Horne-Zeilinger 态，输出态保真度为 0.81。估计的过程保真度为 0.77，表明我们的 Fredkin 门可以应用于各种量子任务。
