Polarization degenerate solid-state cavity QED

A polarization degenerate microcavity containing charge-controlled quantum dots (QDs) enables equal coupling of all polarization degrees of freedom of light to the cavity QED system, which we explore through resonant laser spectroscopy. We first measure interference of the two fine-split neutral QD transitions and find very good agreement of this V-type three-level system with a coherent polarization dependent cavity QED model. We also study a charged QD that suffers from decoherence, and find also in this case that availability of the full polarization degrees of freedom is crucial to reveal the dynamics of the QD transitions. Our results pave the way for postselection-free quantum devices based on electron spin-photon polarization entanglement.