We review a few early studies on atom–photon interactions which took place in France after World War II and before the seventies. Several examples are discussed, including double resonance and optical pumping, radiofrequency multiphoton processes, quantum interference effects in radiative processes, master equation description of atom–photon interactions, optical resonators and laser media, etc. We try to point out the continuity which exists between these early studies and more recent investigations in new research fields, such as laser cooling and trapping. Some general conclusions about science policy will be finally drawn from such a historical review.
We review a few early studies on atom–photon interactions which took place in France after World War II and before the seventies. Several examples are discussed, including double resonance and optical pumping, radiofrequency multiphoton processes, quantum interference effects in radiative processes, master equation description of atom–photon interactions, optical resonators and laser media, etc. We try to point out the continuity which exists between these early studies and more recent investigations in new research fields, such as laser cooling and trapping. Some general conclusions about science policy will be finally drawn from such a historical review.
The review describes and interprets the basic phenomena recently observed in the interaction between free atoms and laser radiation. Some of these have been known for a long time in magnetic resonance but in the optical range, the situation is strongly modified because of spontaneous emission and the Doppler effect. Therefore, particular attention is paid to resonance fluorescence and Doppler-free spectroscopy but without dwelling on applications. Transient effects are also discussed, but all the phenomena which characterize, not specifically the interaction between atoms and fields, but the free evolution of atoms after coherent excitation are ignored. Pulse propagation experiments are described in detail and multiphoton processes are considered, with special emphasis on Doppler-free multiphoton excitation and resonant multiphoton ionization.
Theory of the interaction between atom and radiation field: three pictures in quantum mechanics description two-level atom and the optical Bloch equation quantized description of the radiation field Dicke Hamiltonian and Jaynes - Cummings model quantum theory of a small system coupling to a reservoir. The quantum properties of light: coherence of light squeezed states of light resonance fluorescence superfluorescence optical bistability effects of virtual photon processes. Quantum properties of the atomic behaviour under the interaction of the radiation field: collapses and revivals of the atomic populations squeezing effects of the atomic operators coherent trapping of the atomic population quantum characteristics of a two-atom system under the interaction of radiation field autoionization of the atom in a laser field motion of the atom in a laser field laser cooling.
In this article, we review three areas of study in which the resonant interaction between atoms and laser radiation plays a central role. Firstly, coherent optical transients are discussed in which the direct observation of this interaction can be studied via the detection of the Rabi frequency in optical nutations. Secondly, the response of atoms to resonant radiation in an optical cavity leading to optical bistability and other effects is described. Finally, the new field of atom manipulation by resonant laser fields is introduced, in particular, the deflection of atomic beams. The underlying theoretical framework for the experiments performed is discussed, ranging from full quantum electrodynamic to semiclassical models.
When the Nobel Prize for Physics was awarded to Claude Cohen-Tannoudji, William D. Philipps and Steven Chu in 1997 for the development of methods for cooling and trapping atoms using lasers, this was the reward for two decades of investigations not only touching upon the fundamental aspects of the light–matter interaction, but also leading to a range of applications. On the theoretical level, the advent of this field of research in the late 1970s stimulated the development of various theoretical methods for describing the radiative forces by which light affects the motion of atoms. On the experimental level, judicious use of the radiative forces exerted by lasers made it possible to obtain a drastic reduction of atomic velocities – in other words, to cool an atomic vapour. These advances were characterized by a remarkable cross-fertilization of theoretical and experimental innovations. It was not long before applications began to appear in the field of high-resolution spectroscopy, since ultracold, i.e. slow, atoms can be observed for longer periods, and this allows greater accuracy when measuring atomic resonance frequencies than could be obtained for atoms at room temperature. Based on such resonances, the most accurate clocks in the world use laser-cooled atoms or ions. Atom interferometry is another application of laser manipulation of atoms, which can be applied to measure inertial effects, due for example to the rotation of the Earth or the motion of a vehicle, with an accuracy that already exceeds traditional methods.
Matter–wave interferometry dates from the inception of quantum mechanics, i.e., the early electron diffraction experiments. More recent neutron interferometry experiments have yielded new insights into many fundamental aspects of quantum mechanics. Presently, atom interferometry has been demonstrated and holds promise as a new field of optics – matter–wave optics. This field is particularly interesting since the potential sensitivity of matter–wave interferometers far exceeds that of their light-wave or ‘photon’ antecedents. In this chapter we consider the physics of light-induced forces on the center-of-mass motion of atoms and their application to atom optics (Fig. 17.1). The most obvious being the recoil associated with the emission and absorption of light. This ‘radiation pressure’ is the basis for laser induced cooling. Another very important mechanical effect is the gradient force due to, e.g., transverse variation in the laser beam. These, essentially semiclassical, forces are useful in guiding and trapping neutral atoms. After considering the basic forces which allow us to cool, guide, and trap atoms, we turn to the optics of atomic center-of-mass de Broglie waves, i.e., atom optics. In keeping with the spirit of the present text, we will focus on the quantum limits to matter–wave interferometry. An analysis of a matter–wave gyro in an obvious extension of the laser gyro and the similarity and relative merits of the two will be compared and contrasted. Finally we derive the “recoil limit” to laser cooling; and show that it is possible to supersede this limit via atomic coherence effects.
Abstract: An extensive review of the quantum theory of light-matter interaction is given in this chapter, beginning with its fundamental ideas and historical development. It covers the quantization of the electromagnetic field, atomic models, and important interaction Hamiltonians, including both semi-classical and completely quantum treatments. The role of vacuum fluctuations and fundamental processes like spontaneous and induced emission are examined. Quantum coherence, entanglement, decoherence, and its formal representation using master equations are also covered in this chapter. Modern applications such lasers, quantum sensors, and quantum communication systems are highlighted. The significance of light-matter interaction in furthering quantum science and technology is emphasized in the chapter's conclusion, which also discusses current research trends and future directions. Keywords: Laser, cryptography, Electromagnetic, Quantum, Atomic.