Entanglement is an extraordinary feature of quantum mechanics. Sources of entangled optical photons were essential to test the foundations of quantum physics through violations of Bell’s inequalities. More recently, entangled many-body states have been realized via strong nonlinear interactions in microwave circuits with superconducting qubits. Here, we demonstrate a chip-scale source of entangled optical and microwave photonic qubits. Our device platform integrates a piezo-optomechanical transducer with a superconducting resonator which is robust under optical illumination. We drive a photon-pair generation process and employ a dual-rail encoding intrinsic to our system to prepare entangled states of microwave and optical photons. We place a lower bound on the fidelity of the entangled state by measuring microwave and optical photons in two orthogonal bases. This entanglement source can directly interface telecom wavelength time-bin qubits and gigahertz frequency superconducting qubits, two well-established platforms for quantum communication and computation, respectively.

中文翻译：

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光子量子比特和微波光子量子比特之间的量子纠缠


纠缠是量子力学的一个非凡特征。纠缠光子的来源对于通过违反贝尔不等式来测试量子物理学的基础至关重要。最近，纠缠多体态是通过微波电路中与超导量子比特的强非线性相互作用实现的。在这里，我们展示了纠缠光学和微波光子量子比特的芯片级源。我们的器件平台将压电光机械换能器与超导谐振器集成在一起，该谐振器在光学照明下非常坚固。我们驱动光子对生成过程，并采用系统固有的双轨编码来准备微波和光子的纠缠态。我们通过测量两个正交基中的微波和光学光子来设置纠缠态保真度的下限。该纠缠源可以直接连接电信波长时间区间量子比特和千兆赫兹频率超导量子比特，这两个成熟的量子通信和计算平台分别存在。