Technologies for back side structures on a quantum processor die

A quantum processor die comprising:

• a stack comprising:
• a first layer comprising silicon and germanium;
• a second layer adjacent the first layer, the second layer comprising silicon;
• a third layer adjacent the second layer, the third layer comprising silicon and germanium;
• a first plurality of traces positioned above the stack, wherein traces of the first plurality of traces are positioned less than one micrometer from the second layer;
• and
• a second plurality of traces positioned below the stack, wherein traces of the second plurality of traces are positioned less than one micrometer from the second layer,
• wherein, in response to applied voltages or currents or both, the first plurality of traces and the second plurality of traces are to define a plurality of spin qubits in the stack,
• wherein there is a first distance between the plurality of spin qubits and a nearest trace above the stack and a second distance between the plurality of spin qubits and a nearest trace below the stack, wherein the second distance is at least 20% more or less than the first distance.

A method comprising:

• forming a stack on a wafer, the stack comprising a first layer comprising silicon and germanium, a second layer adjacent the first layer comprising silicon, and a third layer adjacent the second layer comprising silicon and germanium;
• forming a first plurality of traces above the stack after forming the stack;
• and
• forming a second plurality of traces below the stack after forming the first plurality of traces,
• wherein, in response to applied voltages or currents or both, the first plurality of traces and the second plurality of traces are to define a plurality of spin qubits in the stack,
• wherein there is a first distance between the plurality of spin qubits and a nearest trace above the stack and a second distance between the plurality of spin qubits and a nearest trace below the stack, wherein the second distance is at least 20% more or less than the first distance.