Multi-path interferometric Josephson isolator based on nondegenerate three-wave mixing Josephson devices

1. A microwave isolator device comprising:

a first nondegenerate microwave mixer device (first mixer) having a first signal port and a first idler port, the first mixer configured to receive a microwave input of an input frequency via the first signal port, and further configured to generate an idler signal of an idler frequency at the first idler port;

a second nondegenerate microwave mixer device (second mixer) having a second signal port and a second idler port, the second mixer configured to receive the microwave input of the input frequency via the second signal port, and to generate the idler signal of the idler frequency at the second idler port;

a first input/output (I/O) port coupled to the first signal port and the second signal port;

a second I/O port coupled to the first signal port and the second signal port; and

a first microwave pump injecting a first microwave drive into the first mixer at a pump frequency and a first pump phase and a second microwave pump injecting a second microwave drive into the second mixer at the pump frequency and a second pump phase, wherein the pump frequency is equal to the input frequency subtracted from the idler frequency, wherein the first pump phase is adjustable relative to the second pump phase, wherein the phase adjustability is adjusted such that a microwave signal (signal) communicated between the first I/O port and the second I/O port is transmitted while propagating in a first direction between the first I/O port to the second I/O port through the first mixer and the second mixer and to be blocked while propagating in a second direction between the second I/O port to the first I/O port through the first mixer and the second mixer.

2. The microwave isolator device of claim 1 ,

wherein the idler frequency of the idler signal at the first idler port is dependent upon the pump frequency and the input frequency; and

wherein the idler frequency of the idler signal at the second idler port is dependent upon the pump frequency and the input frequency.

3. The microwave isolator device of claim 2 , wherein the first microwave pump is configured to cause the first mixer to operate at a 50:50 beamsplitting working point, and wherein the second microwave pump is configured to cause the second mixer to operate at the 50:50 beamsplitting working point.

4. The microwave isolator device of claim 2 , wherein changing a difference between the first pump phase and the second pump phase causes the signal to be transmitted while propagating in the second direction and blocked while propagating in the first direction.

5. The microwave isolator device of claim 1 , further comprising:

a four-port microwave hybrid device (pump hybrid); and

a microwave pump coupled to the pump hybrid such that a first output port of the pump hybrid injects a first microwave drive into the first mixer at a pump frequency and a first pump phase and a second output port of the pump hybrid injects a second microwave drive into the second mixer at the pump frequency and a second pump phase, wherein the pump hybrid fixes a relative phase between the first microwave drive and the second microwave drive to ±90 degrees.

6. The microwave isolator device of claim 1 , wherein the first idler port and the second idler port are coupled via a transmission line, the transmission line having a negligible energy loss.

7. The microwave isolator device of claim 1 , wherein the first idler port and the second idler port are coupled together using a coupling component, wherein the coupling component introduces an attenuation of a signal that is propagated between the first mixer and the second mixer.

8. The microwave isolator of claim 1 ,

wherein the first idler port of the first mixer comprises a first feedline and a second feedline,

wherein the second idler port of the second mixer comprises a different first feedline and a different second feedline,

wherein the second feedline and the different second feedline are coupled via a transmission line, the transmission line having a negligible energy loss,

wherein the first feedline is coupled to a 50 Ohm termination, and

wherein the different first feedline is coupled to a different 50 Ohm termination.

9. The microwave isolator device of claim 1 , wherein the first and second I/O ports are part of a ninety-degree hybrid coupler, and a function of the first signal port and the second signal port are configured to be equivalent in the first mixer and the second mixer.

10. The microwave isolator device of claim 1 , wherein the first mixer and the second mixer are each a nondegenerate three-wave mixer.

11. The microwave isolator device of claim 1 , wherein the first mixer and the second mixer are each a Josephson parametric converter (JPC), and wherein the first mixer and the second mixer are nominally identical.

12. A method to form a microwave isolator device, the method comprising:

configuring a first nondegenerate microwave mixer device (first mixer) having a first signal port and a first idler port, the first mixer configured to receive a microwave input of an input frequency via the first signal port, and further configured to generate an idler signal of an idler frequency at the first idler port;

configuring a second nondegenerate microwave mixer device (second mixer) having a second signal port and a second idler port, the second mixer configured to receive the microwave input of the input frequency via the second signal port, and to generate the idler signal of the idler frequency at the second idler port;

coupling a first input/output (I/O) port to the first signal port and the second signal port;

coupling a second I/O port to the first signal port and the second signal port;

injecting, from a first microwave pump, a first microwave drive into the first mixer at a pump frequency and a first pump phase; and

injecting, from a second microwave pump, a second microwave drive into the second mixer at the pump frequency and a second pump phase, wherein the pump frequency is equal to the input frequency subtracted from the idler frequency, wherein the first pump phase is adjustable relative to the second pump phase, wherein the phase adjustability is adjusted such that a microwave signal (signal) communicated between the first I/O port and the second I/O port is transmitted while propagating in a first direction between the first I/O port to the second I/O port through the first mixer and the second mixer and to be blocked while propagating in a second direction between the second I/O port to the first I/O port through the first mixer and the second mixer.

13. The method of claim 12 ,

wherein the idler frequency of the idler signal at the second port is dependent upon the pump frequency and the input frequency; and

wherein the idler frequency of the idler signal at the second port is dependent upon the pump frequency and the input frequency.

14. The method of claim 13 , wherein the first microwave pump is configured to cause the first mixer to operate at a 50:50 beamsplitting working point, and wherein the second microwave pump is configured to cause the second mixer to operate at the 50:50 beamsplitting working point.

15. The method of claim 13 , wherein changing a difference between the first pump phase and the second pump phase causes the signal to be transmitted while propagating in the second direction and blocked while propagating in the first direction.

16. The method of claim 12 , further comprising:

coupling a four-port microwave hybrid device (pump hybrid) to a microwave pump such that a first output port of the pump hybrid injects a first microwave drive into the first mixer at a pump frequency and a first pump phase and a second output port of the pump hybrid injects a second microwave drive into the second mixer at the pump frequency and a second pump phase, wherein the pump hybrid fixes a relative phase between the first microwave drive and the second microwave drive to ±90 degrees.

17. The method of claim 12 , wherein the first idler port and the second idler port are coupled via a transmission line, the transmission line having a negligible energy loss.

18. The method of claim 12 , wherein the first idler port and the second idler port are coupled together using a coupling component, wherein the coupling component introduces an attenuation of a signal that is propagated between the first mixer and the second mixer.

19. The method of claim 12 ,

wherein the first idler port of the first mixer comprises a first feedline and a second feedline,

wherein the second idler port of the second mixer comprises a different first feedline and a different second feedline,

wherein the second feedline and the different second feedline are coupled via a transmission line, the transmission line having a negligible energy loss,

wherein the first feedline is coupled to a 50 Ohm termination, and

wherein the different first feedline is coupled to a different 50 Ohm termination.

20. The method of claim 12 , wherein the first and second I/O ports are part of a ninety-degree hybrid coupler, and a function of the first signal port and the second signal port are configured to be equivalent in the first mixer and the second mixer.

21. The method of claim 12 , wherein the first mixer and the second mixer are each a nondegenerate three-wave mixer.

22. The method of claim 12 , wherein the first mixer and the second mixer are each a Josephson parametric converter (JPC), and wherein the first mixer and the second mixer are nominally identical.

23. A superconductor fabrication system which when operated to fabricate a microwave isolator device performing operations comprising:

configuring a first nondegenerate microwave mixer device (first mixer) having a first signal port and a first idler port, the first mixer configured to receive a microwave input of an input frequency via the first signal port, and further configured to generate an idler signal of an idler frequency at the first idler port;

configuring a second nondegenerate microwave mixer device (second mixer) having a second signal port and a second idler port, the second mixer configured to receive the microwave input of the input frequency via the second signal port, and to generate the idler signal of the idler frequency at the second idler port;

coupling a first input/output (I/O) port to the first signal port and the second signal port;

coupling a second I/O port to the first signal port and the second signal port;

injecting, from a first microwave pump, a first microwave drive into the first mixer at a pump frequency and a first pump phase; and

injecting, from a second microwave pump, a second microwave drive into the second mixer at the pump frequency and a second pump phase, wherein the pump frequency is equal to the input frequency subtracted from the idler frequency, wherein the first pump phase is adjustable relative to the second pump phase, wherein the phase adjustability is adjusted such that a microwave signal (signal) communicated between the first I/O port and the second I/O port is transmitted while propagating in a first direction between the first I/O port to the second I/O port through the first mixer and the second mixer and to be blocked while propagating in a second direction between the second I/O port to the first I/O port through the first mixer and the second mixer.

24. The superconductor fabrication system of claim 23 ,

wherein the idler frequency of the idler signal at the second port is dependent upon the pump frequency and the input frequency; and

wherein the idler frequency of the idler signal at the second port is dependent upon the pump frequency and the input frequency.

25. The superconductor fabrication system of claim 24 , wherein the first microwave pump is configured to cause the first mixer to operate at a 50:50 beamsplitting working point, and wherein the second microwave pump is configured to cause the second mixer to operate at the 50:50 beamsplitting working point.