Quantum device and method for controlling quantum device

A method for controlling a quantum device that includes:

• a WTe2 layer that has a first surface and a second surface on an opposite side of the first surface;
• a first insulating layer provided over the first surface;
• a second insulating layer provided over the second surface;
• a first normal conducting metal electrode, a second normal conducting metal electrode, and a third normal conducting metal electrode provided above the first insulating layer;
• and
• superconducting metal wiring that is provided above the second insulating layer and has a first end and a second end, wherein
• in planar view from a direction perpendicular to the first surface,
• the WTe2 layer has a first edge and a second edge that constitute a constricted portion,
• the constricted portion is provided between the first edge and the second edge,
• the first normal conducting metal electrode overlaps a portion of the first edge away from the constricted portion to one side,
• the second normal conducting metal electrode overlaps a portion of the first edge away from the constricted portion to another side, and
• the third normal conducting metal electrode overlaps a portion of the second edge away from the constricted portion to one side, the method comprising:
• controlling a potential of the first normal conducting metal electrode, the second normal conducting metal electrode, and the third normal conducting metal electrode;
• and
• controlling a superconducting phase difference between the first end and the second end.