Ultrastrong coupling between light and matter has, in the past decade, transitioned from a
theoretical idea to an experimental reality. It is a new regime of quantum light–matter …

The Jaynes–Cummings Model (JCM) has recently been receiving increased attention as
one of the simplest, yet intricately nonlinear, models of quantum physics. Emphasising the …

In quantum electrodynamics, the choice of gauge influences the form of light–matter
interactions. However, gauge invariance implies that all physical results should be …

We revisit the derivation of Rabi-and Dicke-type models, which are commonly used for the
study of quantum light-matter interactions in cavity and circuit QED. We demonstrate that the …

Superconducting microwave circuits incorporating nonlinear devices, such as Josephson
junctions, are a leading platform for emerging quantum technologies. Increasing circuit …

Quantum light-matter systems at strong coupling are notoriously challenging to analyze due
to the need to include states with many excitations in every coupled mode. We propose a …

We discuss the construction of low-energy tight-binding Hamiltonians for condensed-matter
systems with a strong coupling to the quantum electromagnetic field. Such Hamiltonians can …

Dissipative quantum phase transition has been widely believed to occur in a Josephson
junction coupled to a resistor despite a lack of concrete experimental evidence. Here, on the …

The interaction between light and matter remains a central topic in modern physics despite
decades of intensive research. Coupling an isolated emitter to a single mode of the …

With the introduction of superconducting circuits into the field of quantum optics, many
experimental demonstrations of the quantum physics of an artificial atom coupled to a single …