Quantum device

A quantum device system comprising:

• a quantum device;
• and
• a sample stage having a cooling function, wherein
• the quantum device comprises:
• a quantum chip;
• and
• an interposer on which the quantum chip is mounted,
• the interposer comprises:
• a substrate;
• and
• a wiring layer disposed on a surface of the substrate on a side thereof on which the quantum chip is located,
• the wiring layer comprises, in at least a part thereof, a first metal layer formed of a superconducting material and a second metal layer formed of a non-superconducting material,
• the quantum device is mounted on the sample stage with the sample stage being in contact with a surface of at least the second metal layer, disposed on a surface of the wiring layer, on a side thereof on which the quantum chip is located.