Controlled Coherent Coupling in a Quantum Dot Molecule Revealed by Ultrafast Four-Wave Mixing Spectroscopy

Semiconductor quantum dot molecules are considered promising candidates for quantum technological applications due to their wide tunability of optical properties and coverage of different energy scales associated with charge and spin physics. While previous works have studied the tunnel-coupling of the different excitonic charge complexes shared by the two quantum dots by conventional optical spectroscopy, we here report on the first demonstration of a coherently controlled interdot tunnel-coupling focusing on the quantum coherence of the optically active trion transitions. We employ ultrafast four-wave mixing spectroscopy to resonantly generate a quantum coherence in one trion complex, transfer it to and probe it in another trion configuration. With the help of theoretical modeling on different levels of complexity, we give an instructive explanation of the underlying coupling mechanism and dynamical processes.

Automated summary

Semiconductor quantum dot molecules are versatile in their tunability of optical properties and their ability to cover different energy scales associated with charge and spin physics, making them promising for quantum technological applications. This study demonstrates the coherent control of interdot tunnel-coupling in these systems, focusing on the quantum coherence of optically active trion transitions. By using ultrafast four-wave mixing spectroscopy, a quantum coherence is generated in one trion complex and transferred and probed in another trion configuration, with theoretical modeling providing an explanation of the underlying coupling mechanism and dynamic processes.