Simulation of Multipartite Cavity Quantum Electrodynamics

Cavity quantum electrodynamics of multipartite systems are studied in depth, which consists of an arbitrary number of emitters in interaction with an arbitrary number of cavity modes. The governing model is obtained by taking the full field-dipole and dipole-dipole interactions into account, and is solved in the Schrödinger picture with assumption of vanishing field and dipole interactions at high energies. An extensive code is developed that is able to solve the system and track its evolution in time, while maintaining sufficient degrees of arbitrariness in setting up the initial conditions and interacting partitions. Using this code, we have been able to numerically evaluate various parameters such as probabilities, expectation values (of field and atomic operators), and the concurrence as the most rigorously defined measure of entanglement of quantum systems. We present and discuss several examples including a seven-partition system consisting of six quantum dots interacting with one cavity mode. We observe for the first time that the behavior of quantum systems under ultrastrong coupling is significantly different than the weakly and strongly coupled systems, marked by onset of chaos and abrupt phase changes. We also discuss how to implement spin into the theoretical picture and thus, successfully simulate a recently reported spin-entanglement experiment.