Light-matter interactions in realistic settings: unifying open quantum systems with macroscopic quantum electrodynamics

"The interaction between light and isolated matter (i.e. single atoms) has been studied for decades. It is well understood, but in reality, no system can be truly isolated from its surroundings which may be highly complex. This difficulty has led to various techniques for dealing with what are known as open quantum systems, where a distinction is made between a 'system' to be studied and an 'environment' with which it interacts.

A related but separate formalism called macroscopic quantum electrodynamics (MQED) aims to describe the interaction of quantum light with dissipative media. Its strengths are in taking into account inhomogeneous objects, such as those needed to calculate Casimir forces between complex objects. The systems described in MQED are similar to those discussed in open quantum systems, but the philosophy and underpinnings of MQED are entirely different. For example, it makes no distinction between the 'system' and 'environment' parts of a given setup.

The question to be answered during this PhD project whether the formalism of MQED can be unified with that of open quantum systems. The resulting theory would have broad applicability; one initial example would be collective effects in energy transfer between vibrationally-active molecules in inhomogeneous environments.

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