Kinetic inductance travelling-wave parametric amplifier (ktwpa) with vacuum gap

A method of fabricating a kinetic inductance travelling-wave parametric amplifier (KTWPA) device, the method comprising;

• providing a first substrate;
• fabricating a superconducting trace on the first substrate, the superconducting trace having a first height;
• fabricating a plurality of spacers on the first substrate, the plurality of spacers having a second height greater than the first height of the superconducting trace;
• providing a second substrate;
• coupling a ground plane to the second substrate;
• coupling the ground plane to the plurality of spacers;
• and
• forming a superconducting transmission line assembly from the superconducting trace and the ground plane separated by a vacuum gap having the second height.

A quantum microwave measurement circuit, comprising:

• a kinetic inductance travelling-wave parametric amplifier (KTWPA) device having an input port and an output port, the KTWPA device further including:
• a first substrate;
• a superconducting trace having a first height fabricated on the first substrate;
• a plurality of spacers having a second height, each of the plurality of spacers fabricated on the first substrate, the second height being greater than the first height of the superconducting trace;
• a ground plane coupled to a second substrate and the plurality of spacers;
• a vacuum gap formed between the first substrate and the ground plane, wherein a superconducting transmission line assembly is formed from the superconducting trace and the ground plane separated by the vacuum gap having the second height;
• and
• a metallic enclosure having a base with an inside top surface, sides, and an enclosure lid, the metallic enclosure forming a vacuum cavity for containing the first substrate and the second substrate to form the vacuum gap;
• a first circulator coupled to a quantum circuit to receive a quantum measurement signal;
• a first microwave triplexer coupled to the first circulator to receive the quantum measurement signal and further coupled to the input port of the KTWPA device, the first microwave triplexer receiving a bias-in voltage and a microwave pump-in signal;
• a second microwave triplexer coupled to the output port of the KTWPA device to receive an amplified quantum measurement signal, the second microwave triplexer receiving a bias-out voltage and a microwave pump-out signal;
• a second circulator coupled to the second microwave triplexer to receive the amplified quantum measurement signal;
• and
• an analog-to-digital converter (ADC) coupled to the second circulator to receive the amplified quantum measurement signal and provide a quantum measurement value, wherein the KTWPA device, the first circulator, the second circulator, the first microwave triplexer and the second microwave triplexer are cooled to less than 100 mK.