Fluctuations can cause extraordinary effects on atoms and nanoparticles. For example, a neutral but polarizable particle sitting close to a planar surface feels an attraction force towards the surface. This is the well-known Casimir-Polder (CP) force. Fluctuations could also induce a quantum frictional force on a moving particle.

This quantum frictional force is different from the classical frictional phenomenon, where a particle slides above a rough surface, because it originates from the quantum and thermal fluctuations of the electromagnetic fields and it is non-contact. In fact, we will see that the frictional force may not even require a surface. It can occur on a particle moving in vacuum, not in contact or close to any other object. But it is also similar to the classical friction, in that both are nonconservative and cause energy transfer between the particle and the background. At finite temperature, the energy transfer accompanying the quantum frictional force is called the radiative heat transfer. This dissertation is devoted to study the quantum frictional force and radiative heat transfer in some simple backgrounds.