Pre-screening and tuning heterojunctions for topological quantum computer

An instrument configured to evaluate a semiconductor-superconductor heterojunction for use in a qubit register of a topological quantum computer, the instrument comprising:

• a controller having a processor and computer memory coupled operatively to the processor, the controller being configured to:
• measure a radio-frequency (RF) junction admittance of the semiconductor-superconductor heterojunction to obtain mapping data;
• find by analysis of the mapping data one or more regions of a parameter space consistent with an unbroken topological phase of the semiconductor-superconductor heterojunction;
• measure a sub-RF conductance including a non-local conductance of the semiconductor-superconductor heterojunction in each of the one or more regions of the parameter space to obtain refinement data;
• and
• find by analysis of the refinement data a boundary of the unbroken topological phase in the parameter space and a topological gap of the semiconductor-superconductor heterojunction for at least one of the one or more regions of the parameter space.

A method for building a topological quantum computer, the method comprising:

• fabricating a semiconductor-superconductor heterojunction having at least three terminals configured to support electronic admittance testing;
• measuring a radio-frequency (RF) junction admittance of the semiconductor-superconductor heterojunction to obtain mapping data;
• finding by analysis of the mapping data one or more regions of a parameter space consistent with an unbroken topological phase of the semiconductor-superconductor heterojunction;
• measuring a sub-RF conductance including a non-local conductance of the semiconductor-superconductor heterojunction in each of the one or more regions of the parameter space to obtain refinement data;
• finding by analysis of the refinement data a boundary of the unbroken topological phase in the parameter space and a topological gap of the semiconductor-superconductor heterojunction for at least one of the one or more regions of the parameter space;
• and
• incorporating the semiconductor-superconductor heterojunction in a qubit register of the topological quantum computer provided that the found boundary and topological gap are within respective, predefined ranges.