Qubits strongly coupled to a photonic crystal give rise to qubit-photon dressed bound states. These bound states, comprising the qubits and spatially localized photonic modes induced around the qubits, are the basis for many exotic physical scenarios. The localization of these states changes with qubit detuning from the photonic crystal band-edge, offering an avenue of in situ control of bound state interaction. Here, we present experimental results from a device with two transmon qubits coupled to a superconducting microwave photonic crystal and realize tunable on-site and inter-bound state interactions. We observe a fourth-order two photon virtual process between bound states indicating strong coupling between the photonic crystal and transmon qubits. Due to their localization-dependent interaction, these states offer the ability to realize one-dimensional chains of bound states with tunable and potentially long-range interactions that preserve the qubits’ spatial organization. The widely tunable, strong and robust interactions demonstrated with this system are promising benchmarks towards realizing larger, more complex systems that use bound states to build and study quantum spin models.

中文翻译：

---

与超导电路相互作用的量子位光子束缚态

与光子晶体强耦合的量子位会产生量子位光子打扮的束缚态。这些束缚态，包括量子位和在量子位周围引发的空间局部光子模式，是许多奇异物理场景的基础。这些状态的定位随着量子位从光子晶体带边缘失谐而变化，从而提供了对结合态相互作用进行原位控制的途径。在这里，我们介绍了具有两个超导微波量子位耦合到超导微波光子晶体的设备的实验结果，并实现了可调谐的现场和束缚态相互作用。我们观察到束缚态之间的四阶两个光子虚拟过程，表明光子晶体和跨子量子位之间的强耦合。由于其依赖本地化的互动，这些状态提供了通过可调谐的和潜在的远程交互作用实现绑定状态的一维链的能力，这些交互作用保留了量子位的空间组织。用该系统演示的广泛可调，强大和鲁棒的相互作用是实现更大，更复杂的系统的基准，这些系统使用绑定状态来构建和研究量子自旋模型，从而成为更大，更复杂的系统。