Driving the common-mode of a Josephson parametric converter using a short-circuited coplanar stripline

1. An on-chip Josephson parametric converter, comprising:

a Josephson ring modulator including four nodes; and

a lossless on-chip flux line capacitively coupled to two adjacent nodes of the four nodes of the Josephson ring modulator, the lossless on-chip flux line having an input port configured to receive a pump drive signal that couples differentially to the two adjacent nodes of the of the Josephson ring modulator, the pump drive signal thereby exciting a common mode of the on-chip Josephson parametric converter;

wherein the lossless on-chip flux line is separate from one or more transmission lines feeding the four nodes.

2. The on-chip Josephson parametric converter of claim 1 , wherein the lossless on-chip flux line is a short-circuited coplanar stripline.

3. The on-chip Josephson parametric converter of claim 2 , wherein the short-circuited coplanar stripline includes a first capacitance between a first node of the two adjacent nodes and the short-circuited coplanar stripline and a second capacitance between a second node of the two adjacent nodes and the short-circuited coplanar stripline.

4. The on-chip Josephson parametric converter of claim 3 , wherein the first capacitance and the second capacitance are respectively based on a proximity of the short-circuited coplanar stripline to the first and second nodes.

5. The on-chip Josephson parametric converter of claim 1 , wherein the lossless on-chip flux line is configured to transmit a high frequency microwave signal as the pump drive signal to the two adjacent nodes of the Josephson ring modulator, the high frequency microwave signal being transmitted via a first capacitor and a second capacitor of first and second nodes of the two adjacent nodes.

6. The on-chip Josephson parametric converter of claim 5 , wherein the high frequency microwave signal ranges from 3-20 gigahertz.

7. The on-chip Josephson parametric converter of claim 1 , further comprising a first resonator and a second resonator that intersect at the Josephson ring modulator and respectively enable a first and a second differential mode of the on-chip Josephson parametric converter.

8. The on-chip Josephson parametric converter of claim 7 , wherein the first resonator, the second resonator, and the lossless on-chip flux line each have a separate input port.

9. The on-chip Josephson parametric converter of claim 7 , wherein the first resonator, the second resonator, the lossless on-chip flux line, and the Josephson ring modulator are each formed of superconducting material.

10. The on-chip Josephson parametric converter of claim 1 , wherein the Josephson ring modulator comprises a plurality of inductors having one end connected together and another end respectively connected to one of the four nodes.

11. A method of forming an on-chip Josephson parametric converter, the method comprising:

forming a Josephson ring modulator including four nodes; and

forming a lossless on-chip flux line capacitively coupled to two adjacent nodes of the four nodes of the Josephson ring modulator, the lossless on-chip flux line having an input port configured to receive a pump drive signal that couples differentially to the two adjacent nodes of the of the Josephson ring modulator, the pump drive signal thereby exciting a common mode of the on-chip Josephson parametric converter;

wherein the lossless on-chip flux line is separate from one or more transmission lines feeding the four nodes.

12. The method of claim 11 , wherein the lossless on-chip flux line is a short-circuited coplanar stripline.

13. The method of claim 12 , wherein the short-circuited coplanar stripline includes a first capacitance between a first node of the two adjacent nodes and the short-circuited coplanar stripline and a second capacitance between a second node of the two adjacent nodes and the short-circuited coplanar stripline.

14. The method of claim 13 , wherein the first capacitance and the second capacitance are respectively based on a proximity of the short-circuited coplanar stripline to the first and second nodes.

15. The method of claim 11 , wherein the lossless on-chip flux line is configured to transmit a high frequency microwave signal as the pump drive signal to the two adjacent nodes of the Josephson ring modulator, the high frequency microwave signal being transmitted via a first capacitor and a second capacitor of first and second nodes of the two adjacent nodes.

16. The method of claim 15 , wherein the high frequency microwave signal ranges from 3-20 gigahertz.

17. The method of claim 11 , wherein a first resonator and a second resonator intersect at the Josephson ring modulator and respectively enable a first and a second differential mode of the on-chip Josephson parametric converter.

18. The method of claim 17 , wherein the first resonator, the second resonator, and the lossless on-chip flux line each have a separate input port;

wherein the first resonator, the second resonator, the lossless on-chip flux line, and the Josephson ring modulator are each formed of superconducting material; and

wherein the Josephson ring modulator comprises a plurality of inductors having one end shunted and another end respectively connected to one of the four nodes.

19. A method of injecting a pump drive to an on-chip Josephson parametric converter, the method comprising:

providing a lossless on-chip flux line in a proximity to a Josephson ring modulator of the on-chip Josephson parametric converter such that the lossless on-chip flux line couples capacitively to two adjacent nodes of the Josephson ring modulator; and

transmitting a microwave signal as the pump drive to the on-chip Josephson parametric converter using the lossless on-chip flux line;

wherein the lossless on-chip flux line is separate from one or more transmission lines feeding the two adjacent nodes.

20. The method of claim 19 , wherein the lossless on-chip flux line is a short-circuited coplanar stripline.