Gate-Based Protocol Simulations for Quantum Repeaters using Quantum-Dot Molecules in Switchable Electric Fields

Electrically controllable quantum-dot molecules (QDMs) are a promising platform for deterministic entanglement generation and, as such, a resource for quantum-repeater networks. A microscopic open-quantum-systems approach based on a time-dependent Bloch–Redfield equation is developed to model the generation of entangled spin states with high fidelity. The state preparation is a crucial step in a protocol for deterministic entangled-photon-pair generation that is proposed for quantum repeater applications. The theory takes into account the quantum-dot molecules' electronic properties that are controlled by time-dependent electric fields as well as dissipation due to electron–phonon interaction. The transition between adiabatic and non-adiabatic regimes is quantified, which provides insights into the dynamics of adiabatic control of QDM charge states in the presence of dissipative processes. From this, the maximum speed of entangled-state preparation is inferred under different experimental conditions, which serves as a first step toward simulation of attainable entangled photon-pair generation rates. The developed formalism opens the possibility for device-realistic descriptions of repeater protocol implementations.