Quantum Dot Molecule Devices with Optical Control of Charge Status and Electronic Control of Coupling

Tunnel-coupled pairs of optically active quantum dots - dot molecules (QDMs) offer the possibility to combine excellent optical properties such as strong light-matter coupling with two-spin singlet-triplet ($S-T_0$) qubits having extended coherence times. The $S-T_0$ basis formed using two spins is inherently protected against electric and magnetic field noise. However, since a single gate voltage typically used stabilize charge occupancy control inter-dot orbital couplings, operation under optimal conditions remains challenging. Here, we present an tunable QDM that can be charged one (1h) or holes (2h) on demand. We perform four-phase sequence facilitates sequential preparation 2h state subsequently allows flexible coupling. Charges are loaded via pumping electron tunnel ionization. achieve one- two-hole charging efficiencies 93.5 $\pm$ 0.8 % 80.5 1.3 %, respectively. Combining efficient precise setting few-spin qubits, would required for on-demand generation two-dimensional photonic cluster states transduction between microwaves photons.