This paper reviews recent experimental and theoretical progress concerning many-body phenomena in dilute, ultracold gases. It focuses on effects beyond standard weak-coupling descriptions, such as the Mott-Hubbard transition in optical lattices, strongly interacting gases in one and two dimensions, or lowest-Landau-level physics in quasi-two-dimensional gases in fast rotation. Strong correlations in fermionic gases are discussed in optical lattices or near-Feshbach resonances in the BCS-BEC crossover.

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Many-Body Physics with Ultracold Gases

In this review we look at the concepts and state-of-the-art concerning the strong coupling of surface plasmon-polariton modes to states associated with quantum emitters such as excitons in J-aggregates, dye molecules and quantum dots. We explore the phenomenon of strong coupling with reference to a number of examples involving electromagnetic fields and matter. We then provide a concise description of the relevant background physics of surface plasmon polaritons. An extensive overview of the historical background and a detailed discussion of more recent relevant experimental advances concerning strong coupling between surface plasmon polaritons and quantum emitters is then presented. Three conceptual frameworks are then discussed and compared in depth: classical, semi-classical and fully quantum mechanical; these theoretical frameworks will have relevance to strong coupling beyond that involving surface plasmon polaritons. We conclude our review with a perspective on the future of this rapidly emerging field, one we are sure will grow to encompass more intriguing physics and will develop in scope to be of relevance to other areas of science.

https://iopscience.iop.org/article/10.1088/0034-4885/78/1/013901/pdf

Strong coupling between surface plasmon polaritons and emitters: a review

The Jaynes-Cummings model (JCM), a soluble fully quantum mechanical model of an atom in a field, was first used (in 1963) to examine the classical aspects of spontaneous emission and to reveal the existence of Rabi oscillations in atomic excitation probabilities for fields with sharply defined energy (or photon number). For fields having a statistical distributions of photon numbers the oscillations collapse to an expected steady value. In 1980 it was discovered that with appropriate initial conditions (e.g. a near-classical field), the Rabi oscillations would eventually revive, only to collapse and revive repeatedly in a complicated pattern. The existence of these revivals, present in the analytic solutions of the JCM, provided direct evidence for discreteness of field excitation (photons) and hence for the truly quantum nature of radiation. Subsequent study revealed further non-classical properties of the JCM field, such as a tendency of the photons to antibunch. Within the last two years it ha...

The Jaynes-Cummings Model

This paper reviews the work on cavity quantum electrodynamics of free atoms. In recent years, cavity experiments have also been conducted on a variety of solid-state systems resulting in many interesting applications, of which microlasers, photon bandgap structures and quantum dot structures in cavities are outstanding examples. Although these phenomena and systems are very interesting, discussion is limited here to free atoms and mostly single atoms because these systems exhibit clean quantum phenomena and are not disturbed by a variety of other effects. At the centre of our review is the work on the one-atom maser, but we also give a survey of the entire field, using free atoms in order to show the large variety of problems dealt with. The cavity interaction can be separated into two main regimes: the weak coupling in cavity or cavity-like structures with low quality factors Q and the strong coupling when high-Q cavities are involved. The weak coupling leads to modification of spontaneous transitions and level shifts, whereas the strong coupling enables one to observe a periodic exchange of photons between atoms and the radiation field. In this case, atoms and photons are entangled, this being the basis for a variety of phenomena observed, some of them leading to interesting applications in quantum information processing. The cavity experiments with free atoms reached a new domain with the advent of experiments in the visible spectral region. A review on recent achievements in this area is also given.

https://iopscience.iop.org/article/10.1088/0034-4885/69/5/R02/pdf

Cavity quantum electrodynamics

The emerging field of circuit quantum electrodynamics could pave the way for the design of practical quantum computers.

Wiring up quantum systems

The dynamics of the interaction of a single Rydberg atom with a single mode of an electromagnetic field in a superconducting cavity was investigated. Velocity-selected atoms were used and the evolution of the atomic inversion as atom and field exchange energy was observed. The quantum collapse and revival predicted by the Jaynes-Cummings model were demonstrated experimentally for the first time. The evaluation of the dynamic behavior of the atoms allows us to determine the statistics of the few photons in the cavity.

Norbert Klein

Papers

Observation of quantum collapse and revival in a one-atom maser.