Quantum well stacks for quantum dot devices

A quantum computing device, comprising:

• a quantum processing device, wherein the quantum processing device includes a quantum well stack including a quantum well layer and a buffer layer, the quantum well layer includes first isotopically purified material, the buffer layer includes a second isotopically purified material, and the quantum processing device further includes at least one gate above the quantum well stack to control quantum dot formation in the quantum well stack;
• and
• a non-quantum processing device, coupled to the quantum processing device, to control voltages applied to the at least one gate,
• wherein:
• the gate at least one gate includes a gate dielectric,
• the quantum well layer is between the buffer layer and the gate dielectric,
• the quantum computing device further includes a barrier layer, and
• the buffer layer is between the quantum well layer and the barrier layer.

A quantum dot device, comprising:

• a quantum well stack including a quantum well layer, wherein the quantum well layer includes an isotopically purified material;
• and
• a gate above the quantum well stack;
• wherein the isotopically purified material includes at least one of zinc, cadmium, tellurium, selenium, sulfur, iron, lead, tin, and carbon.