Many-Body Quantum Optics and Light-Matter Interactions in Superconducting Circuits

这个项目的目标是研究当这种相互作用变得异常强烈时，光如何与物质相互作用。科学家们早就知道光是如何与块状物质相互作用的：例如，当它进入玻璃时，它会从表面反射并弯曲。最近，科学家们开始探索光与物质相互作用的极端。当单个光子(光的粒子)与单个原子相互作用时会发生什么？原子可以吸收或发射一个光子，但如果把它放在两面镜子之间，它可以吸收和重新发射同一个光子多次。当这种情况发生时，原子和光子就形成了一个新的集体系统，就像原子和光子之间的一个分子。在这种情况下，这种相互作用被认为是强烈的。在这个项目中，目标是探索当相互作用变得更强，以及涉及更多光子时会发生什么。特别是，科学家们预测光本身将经历相变(就像水变成冰一样)。在这里，图案化的金属电路，就像计算机芯片中的电路，将被用来研究微波光子和人造原子之间的相互作用。特别是，主要目的是观察这些微波光子的相变，并研究出现的光的新特性。这将让我们深入了解相互作用如何导致复杂的新行为，这是贯穿于大部分科学和技术领域的一个主题。此外，将用于研究这一点的特定电路也将用于建造一种名为量子计算机的新型计算机；这些电路的改进是一个附带的好处。这一提议的具体目的是研究相互作用光子系统中光的多体状态的出现。有效的光子-光子相互作用将由超导微波电路产生，有效相互作用由约瑟夫森结量子比特介导。将使用两种不同的体系结构来研究这些相变。首先，微波腔阵列，每个耦合到超导量子比特，将被用来产生相互作用的微波光子晶格。晶格将被稳态驱动和耗散填充，在适当的条件下，这将导致稳态、非平衡相变。我们将探索这种相变和稳态的本质。第二，超导量子比特将被放置在光子带隙介质中。这些量子比特将导致束缚单光子态的产生；多个量子比特将导致束缚光子重叠，产生一个高度可调的晶格来研究这些多体量子光学效应。这个项目为研究冷原子的相变提供了一个补充方法，并且可以很容易地获得系统的非平衡物理和输运性质。

The goal of this project is to study how light interacts with matter when that interaction becomes extraordinarily strong. Scientists have long understood how light interacts with bulk matter: for example, it can reflect off surfaces and bend when it enters glass. More recently, scientists have begun to explore the extremes of light-matter interaction. What happens when a single photon (particle of light) interacts with a single atom? The atom can either absorb or emit one photon, but if it is placed between two mirrors, it can absorb and re-emit the same photon many times. When this happens, the atom and photon form a new collective system, like a molecule between the atom and the photon. In this case, the interaction is said to be strong. In this project, the goal is to explore what happens when the interaction becomes still stronger, and more photons become involved. In particular, scientists have predicted that light itself will undergo a phase transition (like when water turns into ice). Here, patterned metal circuits, like those in a computer chip, will be used to study the interaction between microwave photons and artificial atoms. In particular, the chief aim is to observe a phase transition for these microwave photons and to study the new properties of light that emerge. This will give insight into how interactions lead to complex new behavior, a theme that runs throughout much of science and technology. Moreover, the specific circuits that will be used to study this are also used for building a new type of computer called a quantum computer; improvement in these circuits is an ancillary benefit. The specific aim of this proposal is to study the emergence of many-body states of light in systems of interacting photons. Effective photon-photon interactions will be generated using superconducting microwave circuits, with effective interactions mediated by Josephson-junction qubits. Two different architectures will be used to study these phase transitions. First, arrays of microwave cavities, each coupled to a superconducting qubit, will be used to generate a lattice of interacting microwave photons. The lattice will be populated with a steady state drive and dissipation, which, under appropriate conditions, will lead to a steady-state, non-equilibrium phase transition. The nature of this phase transition and of the steady states will be explored. Second, superconducting qubits will be placed in a photonic bandgap medium. These qubits will result in the generation of bound single photon states; multiple qubits will result in overlapping bound photons, generating a highly tunable lattice to study these many-body quantum optics effects. This project provides a complementary approach to studying phase transitions with cold atoms, and can easily access non-equilibrium physics and transport properties of the system.