Signal transmission loss in a quantum network can be overcome by encoding quantum states in complex multiphoton fields. But transmitting quantum information encoded in this way requires that locally stored states can be converted to propagating fields. Here we experimentally show the controlled conversion of multiphoton quantum states, such as Schrödinger cat states, from a microwave cavity quantum memory into propagating modes. By parametric conversion using the nonlinearity of a single Josephson junction, we can release the cavity state in ~500 ns, about three orders of magnitude faster than its intrinsic lifetime. This mechanism—which we dub Schrödinger’s catapult—faithfully converts arbitrary cavity fields to travelling signals with an estimated efficiency of >90%, enabling the on-demand generation of complex itinerant quantum states. Importantly, the release process can be precisely controlled on fast timescales, allowing us to generate entanglement between the cavity and the travelling mode by partial conversion.

中文翻译：

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从微波腔存储器中控制释放多光子量子态

可以通过在复杂的多光子场中编码量子态来克服量子网络中的信号传输损耗。但是，传输以这种方式编码的量子信息需要将本地存储的状态转换为传播场。在这里，我们实验显示了多光子量子态（例如Schrödinger猫态）从微波腔量子存储到传播模式的受控转换。通过使用单个约瑟夫森结的非线性进行参数转换，我们可以在约500  ns内释放腔态，比其固有寿命快约三个数量级。我们将这种机制称为Schrödinger '弹射器-忠实地将任意腔场转换为传播信号，估计效率> 90％，从而可以按需生成复杂的迭代量子态。重要的是，释放过程可以在快速的时间尺度上精确控制，从而使我们能够通过部分转换在空腔和行进模式之间产生纠缠。