MC2, Chalmers University of Technology, Göteborg, Sweden.
Phys Rev Lett. 2011 Aug 12;107(7):073601. doi: 10.1103/PhysRevLett.107.073601. Epub 2011 Aug 9.
We have embedded an artificial atom, a superconducting transmon qubit, in an open transmission line and investigated the strong scattering of incident microwave photons (∼6 GHz). When an input coherent state, with an average photon number N≪1 is on resonance with the artificial atom, we observe extinction of up to 99.6% in the forward propagating field. We use two-tone spectroscopy to study scattering from excited states and we observe electromagnetically induced transparency (EIT). We then use EIT to make a single-photon router, where we can control to what output port an incoming signal is delivered. The maximum on-off ratio is around 99% with a rise and fall time on the order of nanoseconds, consistent with theoretical expectations. The router can easily be extended to have multiple output ports and it can be viewed as a rudimentary quantum node, an important step towards building quantum information networks.
我们将一个人造原子（超导转导量子比特）嵌入到一个开放式传输线中，并研究了入射微波光子的强散射（约 6GHz）。当输入的相干态（平均光子数 N≪1）与人造原子共振时，我们观察到正向传播场中的消光率高达 99.6%。我们使用双音光谱法研究了从激发态散射的情况，并观察到了电磁感应透明（EIT）。然后，我们使用 EIT 来制作单光子路由器，我们可以控制输入信号被传送到哪个输出端口。最大的开关比约为 99%，上升和下降时间在纳秒量级，与理论预期一致。该路由器可以很容易地扩展到具有多个输出端口，它可以被看作是一个基本的量子节点，这是朝着构建量子信息网络迈出的重要一步。
