EXPLORING NONLINEAR QUANTUM DYNAMICS WITH SUPERCONDUCTING CIRCUITS

电路量子电动力学（QED）器件通常由“人造原子”组成，其中包含约瑟夫森结（JJ），与微波腔内的电磁场模式耦合。这种系统促进了微波电磁场与人造原子之间的强相互作用，同时抑制了退相干。电路QED已经被证明是探索量子物理的一种非常富有成效的工具，在多体量子物理、超强光-物质耦合、高度非经典状态的产生和量子真空涨落等领域开辟了令人兴奋的新研究途径。该项目旨在开发一种新型电路qed器件的理论模型，其中JJ嵌入微波腔中，施加直流偏置电压而不是交流控制场，从而导致电荷电流流过器件。这样的系统将物理学的两个重要子领域结合在一起：电荷的量子输运（即库珀对）和微波腔中光子的量子光学。此外，电荷和光子之间的相互作用是高度非线性的，可以做得特别强。该项目将探索这些系统的迷人物理特性，以及它们与其他驱动耗散量子系统的联系。

Circuit quantum electrodynamics (QED) devices typically consist of 'artificial atoms' containing Josephson junctions (JJ) coupled to modes of the electromagnetic field confined within a microwave cavity. Such systems facilitate strong interactions between the microwave electromagnetic field and the artificial atoms, whilst at the same time suppressing decoherence. Circuit QED has already proved an extremely fruitful tool for exploring quantum physics, opening up exciting new avenues of research in areas as diverse as many-body quantum physics, ultra-strong light-matter coupling the production of highly non-classical states and quantum vacuum fluctuations. This project aims to develop theoretical models for a new class of circuit-QED devices in which a JJ is embedded within a microwave cavity and a dc bias voltage applied rather than ac control fields, leading to the flow of a current of charges through the device. Such systems bring together two important subfields of physics: the quantum transport of charge (i.e. Cooper pairs) and the quantum optics of photons in the microwave cavity. Furthermore, the interactions between charges and photons are highly nonlinear and can be made exceptionally strong. The project will explore the fascinating physics of such systems and their connections with other driven-dissipative quantum systems.