Institute for Quantum Science and Technology, Department of Physics & Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada.
Nat Commun. 2013;4:2386. doi: 10.1038/ncomms3386.
Quantum memories allowing reversible transfer of quantum states between light and matter are central to quantum repeaters, quantum networks and linear optics quantum computing. Significant progress regarding the faithful transfer of quantum information has been reported in recent years. However, none of these demonstrations confirm that the re-emitted photons remain suitable for two-photon interference measurements, such as C-NOT gates and Bell-state measurements, which constitute another key ingredient for all aforementioned applications. Here, using pairs of laser pulses at the single-photon level, we demonstrate two-photon interference and Bell-state measurements after either none, one or both pulses have been reversibly mapped to separate thulium-doped lithium niobate waveguides. As the interference is always near the theoretical maximum, we conclude that our solid-state quantum memories, in addition to faithfully mapping quantum information, also preserve the entire photonic wavefunction. Hence, our memories are generally suitable for future applications of quantum information processing that require two-photon interference.
量子存储器能够在光与物质之间可逆地转移量子态，是量子中继器、量子网络和线性光学量子计算的核心。近年来，在忠实传输量子信息方面已经取得了重大进展。然而，这些演示中没有一个证实重新发射的光子仍然适合用于双光子干涉测量，例如 C-NOT 门和贝尔态测量，这些测量是所有上述应用的另一个关键组成部分。在这里，我们使用单光子级别的激光脉冲对，证明了在没有、一个或两个脉冲都被可逆地映射到单独的掺铥锂铌酸光波导之后，双光子干涉和贝尔态测量。由于干涉总是接近理论最大值，因此我们得出结论，我们的固态量子存储器除了忠实地映射量子信息外，还保留了整个光子波函数。因此，我们的存储器通常适用于需要双光子干涉的未来量子信息处理应用。
