Low-loss infrared filter for microwave measurement which integrates a distributed bragg reflector into a microwave transmission line

1. A microwave apparatus, the apparatus comprising:

a microwave system configured to output a microwave readout signal, the microwave system having an input and an output;

an output microwave transmission line connected to the output of the microwave system; and

a distributed Bragg reflector, integrated into a transmission line geometry, configured as a low-loss infrared filter that blocks infrared radiation while allowing transmission of the microwave readout signal, the low-loss infrared filter being connected to the output microwave transmission line.

2. The apparatus of claim 1 , further comprising:

an input microwave transmission line connected to the input of the microwave system; and

another distributed Bragg reflector, integrated into the transmission line geometry, configured as another low-loss infrared filter that blocks infrared radiation while allowing transmission of a microwave read signal and a microwave qubit signal;

wherein the low-loss infrared filter is connected to the input microwave transmission line.

3. The apparatus of claim 1 , wherein the distributed Bragg reflector comprises a unit cell of at least two different dielectric layers.

4. The apparatus of claim 3 , wherein the unit cell repeats to have a total of N dielectric layers.

5. The apparatus of claim 1 , wherein the distributed Bragg reflector comprises a first dielectric layer and a second dielectric layer adjacent to the first dielectric layer.

6. The apparatus of claim 5 , wherein the first dielectric layer has a first dielectric constant; and

wherein the second dielectric layer has a second dielectric constant different from the first dielectric constant.

7. The apparatus of claim 5 , wherein the first dielectric layer has a first thickness; and

wherein the second dielectric layer has a second thickness.

8. The apparatus of claim 7 , wherein the first thickness is different from the second thickness.

9. The apparatus of claim 5 , wherein the low-loss infrared filter has a center conductor stripline formed through the first dielectric layer and the second dielectric layer.

10. The apparatus of claim 9 , wherein the center conductor stripline is a conductive metal.

11. The apparatus of claim 9 , wherein the low-loss infrared filter has an outer conductor encompassing the first dielectric layer and the second dielectric layer, the center conductor stripline extending through the outer conductor in a lengthwise direction;

wherein the low-loss infrared filter comprises a first connector and a second connector, both connected to opposite ends of the center conductor stripline in the lengthwise direction; and

wherein an outer conductor of the first and second connectors connects to the outer conductor of the low-loss infrared filter.