Low loss broadband quantum limited Floquet-mode amplifier
A Floquet mode traveling wave parametric amplifier (TWPA) is disclosed. The Floquet mode TWPA comprises a plurality of stages, where each stage is made up of a nonlinear element and a shunt capacitor. The nonlinear elements may be Josephson junctions, or a combination of series and/or parallel Josephson junctions. The Floquet mode TWPA is designed such that the critical current of the nonlinear elements in each stage is not constant. In some embodiments, the ratio of the largest critical current to the smallest critical current in the Floquet mode TWPA is at least 2:1. In some embodiments, the nonlinear elements with the largest critical current are disposed at or near the input or output of the amplifier. In this way, reflections and backward amplification may be minimized. Further, the TWPA is formed using planar capacitors on a high resistivity substrate, or using low loss parallel plate capacitors.
1. A Floquet mode traveling wave parametric amplifier (TWPA), having an input and an output, comprising:
a circuit having a plurality of stages, wherein each stage comprises a nonlinear element and a capacitor, wherein a critical current of the nonlinear element decreases monotonically from the input to a trough and increases from the trough to the output, wherein the trough is defined as a continuous series of stages wherein each stage in the trough has a critical current within 5% of a minimum critical current, and wherein at least 10% of the stages are in the trough.
2. The Floquet mode TWPA of claim 1 , wherein an expanded trough is defined as a continuous series of stages wherein each stage in the expanded trough has a critical current within 10% of the minimum critical current, wherein at least 30% of the stages are in the expanded trough.
3. The Floquet mode TWPA of claim 2 , wherein at least 40% of the stages are in the expanded trough.
4. The Floquet mode TWPA of claim 1 , wherein a ratio of a maximum critical current to the minimum critical current is at least 2.
5. The Floquet mode TWPA of claim 1 , wherein the nonlinear element comprises a Josephson junction or a plurality of Josephson junctions arranged in series, in parallel or a combination of serial and parallel.
6. The Floquet mode TWPA of claim 1 , wherein the circuit is disposed on a substrate having a resistivity greater than 1000 Ωcm and the capacitor comprises a planar capacitor.
7. The Floquet mode TWPA of claim 1 , wherein the capacitor comprises a parallel plate capacitor wherein a dielectric material between parallel plates is formed using controlled in-situ oxidation.
8. The Floquet mode TWPA of claim 1 , wherein each capacitor is configured such that an impedance of a stage is within 20% of an adjacent stage.
9. The Floquet mode TWPA of claim 1 , wherein a graph of critical current as a function of stage number, excluding the trough, is an inverse Gaussian curve.
10. The Floquet mode TWPA of claim 1 , wherein the nonlinear elements are chained together and the capacitors comprise shunt capacitors.
11. A Floquet mode traveling wave parametric amplifier (TWPA), having an input and an output, comprising:
a circuit having a plurality of stages, wherein each stage comprises a nonlinear element and a capacitor, wherein a ratio of a largest critical current of one of the nonlinear elements to a smallest critical current of another of the nonlinear elements is between 2 and 5.
12. The Floquet mode TWPA of claim 11 , wherein the nonlinear element comprises a Josephson junction or a plurality of Josephson junctions arranged in series, in parallel or a combination of serial and parallel.
13. The Floquet mode TWPA of claim 11 , wherein the one of the nonlinear elements with the largest critical current is the nonlinear element disposed in the stage adjacent to the input or the output.
14. The Floquet mode TWPA of claim 11 , wherein the circuit is disposed on a substrate having a resistivity greater than 1000 Ωcm and the capacitor comprises a planar capacitor.
15. The Floquet mode TWPA of claim 11 , wherein the capacitor comprises a parallel plate capacitor wherein a dielectric material between parallel plates is formed using controlled in-situ oxidation.
16. The Floquet mode TWPA of claim 11 , wherein the nonlinear elements are chained together and the capacitors comprise shunt capacitors.
17. A Floquet mode traveling wave parametric amplifier (TWPA), having an input and an output, comprising:
a circuit having a plurality of stages, including an input stage at the input, an output stage at the output;
wherein each stage comprises a nonlinear element and a capacitor and each nonlinear element has a critical current;
wherein a segment is defined as a chain of stages having an electrical length equal to one wavelength of interest,
wherein the segment comprising the stage adjacent to the input is defined as an input segment;
wherein the segment comprising a stage having a smallest critical current is defined as a high gain segment; and
wherein a ratio of an average of critical currents in the input segment to the average of critical currents in the high gain segment is between 2 and 4.
18. The Floquet mode TWPA of claim 17 , wherein the segment comprising the stage adjacent to the output is defined as an output segment;
wherein the ratio of the average of critical currents in the output segment to the average of critical current in the high gain segment is between 2 and 4.
19. The Floquet mode TWPA of claim 17 , wherein the wavelength of interest is between 30 μm and 3 meters.
20. The Floquet mode TWPA of claim 17 , wherein each segment comprises at least five stages.
21. The Floquet mode TWPA of claim 17 , wherein the circuit has an electrical length of at least five wavelengths.
22. The Floquet mode TWPA of claim 17 , wherein the nonlinear elements are chained together and the capacitors comprise shunt capacitors.
23. The Floquet mode TWPA of claim 1 , wherein the capacitor comprises a parallel plate capacitor wherein a dielectric material between parallel plates is formed using atomic layer deposition.
24. The Floquet mode TWPA of claim 11 , wherein the capacitor comprises a parallel plate capacitor wherein a dielectric material between parallel plates is formed using atomic layer deposition.