Microwave integrated quantum circuits with cap wafer and methods for making the same

A method of fabricating a quantum computing system, the method comprising:

• forming a quantum circuit device on a first substrate, the first substrate having a first surface on which the quantum processing device is disposed and a second, opposing surface;
• forming bonding elements adapted to contact one of the surfaces of the first substrate and a first surface of a second substrate;
• forming spacers on one of the surfaces of the first substrate or the second substrate adapted to face each other, wherein the spacers are adapted to contact the surfaces of the first substrate and the second substrate adapted to face each other to cause a separation thereof that is substantially equal to a height of the spacers, and the spacers comprise insulating standoff bumps;
• and
• forming an electrically conducting layer disposed on the first surface of the second substrate that conforms to the insulating standoff bumps.

A quantum computing system comprising:

• a quantum circuit device;
• a first substrate having a first surface on which the quantum processing device is disposed and a second, opposing surface;
• a second substrate having a first surface;
• bonding elements in contact with one of the surfaces of the first substrate and the first surface of the second substrate;
• spacers disposed on one of the surfaces of the first substrate or the second substrate that face each other, wherein the spacers are in contact with the surfaces of the first substrate and the second substrate that face each other to cause a separation thereof that is substantially equal to a height of the spacers, and the spacers comprise insulating standoff bumps;
• and
• an electrically conducting layer disposed on the first surface of the second substrate that conforms to the insulating standoff bumps.