Frequency multiplexed resonator input and/or output for a superconducting device
A superconducting input and/or output system employs at least one microwave superconducting resonator. The microwave superconducting resonator(s) may be communicatively coupled to a microwave transmission line. Each microwave superconducting resonator may include a first and a second DC SQUID, in series with one another and with an inductance (e.g., inductor), and a capacitance in parallel with the first and second DC SQUIDs and inductance. Respective inductive interfaces are operable to apply flux bias to control the DC SQUIDs. The second DC SQUID may be coupled to a Quantum Flux Parametron (QFP), for example as a final element in a shift register. A superconducting parallel plate capacitor structure and method of fabricating such are also taught.
1. A superconducting input/output system comprising:
a microwave transmission line;
at least one microwave superconducting resonator communicatively coupled to the microwave transmission line, each microwave superconducting resonator respectively comprising:
a capacitance coupled between the microwave transmission line and a first node via a superconductive path;
an inductance coupled between the microwave transmission line and the first node via a superconductive path, the inductance in parallel with the capacitance of the respective microwave superconducting resonator;
a first DC superconducting quantum interference device (SQUID) coupled between the inductance and the first node via a superconductive path, in parallel with the capacitance of the respective microwave superconducting resonator and in series with the inductance of the respective microwave superconducting resonator; and
a second DC superconducting quantum interference device (SQUID) coupled between the first DC SQUID and the first node via a superconductive path, in parallel with the capacitance of the respective microwave superconducting resonator and in series with the inductance of the respective microwave superconducting resonator and in series with the first DC SQUID of the respective microwave superconducting resonator;
a first interface inductively coupled to the first DC SQUID and selectively operable to apply a first flux bias to the first DC SQUID; and
a second interface inductively coupled to the second DC SQUID and selectively operable to apply a second flux bias to the second DC SQUID, wherein the second DC SQUID is communicatively coupled to a Quantum Flux Parametron (QFP).
2. The superconducting input/output system of claim 1 wherein the second DC SQUID is inductively coupled to the QFP.
3. The superconducting input/output system of claim 1 wherein the QFP is a shift register and the second DC SQUID is communicatively coupled to an endpoint of the shift register, the shift register comprising a plurality of stages.
4. The superconducting input/output system of claim 3 wherein the at least one microwave superconducting resonator comprises a plurality of microwave superconducting resonators, each of the plurality of microwave superconducting resonators communicatively coupled to the microwave transmission line.
5. The superconducting input/output system of claim 1 wherein the superconducting input/output system is a frequency multiplexed resonator transceiver selectively operable to readout data from the QFP and load data into the QFP.
6. The superconducting input/output system of claims 1 further comprising:
a microwave subsystem operable to generate a microwave signal for transmission on the microwave transmission line, and operable to receive a microwave signal via the microwave transmission line, the microwave subsystem comprising:
a pair of complex mixers, a first one of the complex mixers communicatively coupled to the at least one DAC and a second one of the complex mixers communicatively coupled to the at least one ADC;
a reference microwave signal generator communicatively coupled to provide a reference microwave signal to at least one of the complex mixers;
a programmable attenuator communicatively coupled to the complex mixers; and
a microwave switch operable to control passage of the signals between the first one of the complex mixers and the programmable attenuator; and
at least one amplifier communicatively coupled to receive a signal from the programmable attenuator.
7. The superconducting input/output system of claim 6 further comprising:
a digital electronics subsystem operable to generate a baseband signal for input to the microwave subsystem, and operable to detect a baseband signal received from the microwave subsystem, the digital electronics subsystem comprising:
a Field Programmable Gate Array (FPGA);
at least one Digital-to-Analog Converter (DAC) communicatively coupled to an output of the FPGA; and
at least one Analog-to-Digital Converter (ADC) communicatively coupled to an input of the FPGA.
8. The superconducting input/output system of claims 1 wherein the first flux bias applied by the first interface tunes the resonant frequency of the first microwave resonator, and the second flux bias applied by the second interface tunes the sensitivity of the first microwave resonator.
9. The superconducting input/output system of claim 8 wherein the third flux bias applied by the third interface causes partial annealing.
10. The superconducting input/output system of claim 9 wherein partial annealing includes lowering the potential barrier between two stable energy states of the QFP.
11. The superconducting input/output system of claims 1 wherein the capacitance comprises a parallel plate capacitor.
12. The superconducting input/output system of claims 1 wherein the inductance comprises a spiral inductor.
13. The superconducting input/output system of claims 1 wherein the superconducting input/output system includes a superconducting readout system operable to read out the states of one or more superconducting devices.
14. The superconducting input/output system of claim 13 wherein at least one of the one or more superconducting devices is a superconducting qubit.
15. The superconducting input/output system of claim 1 wherein the superconducting input/output system includes a superconducting data input system operable to load data into one or more superconducting devices.
16. The superconducting input/output system of claim 15 wherein at least one of the one or more superconducting devices is a DAC.
17. The superconducting input/output system of claim 1 wherein the QFP is a final stage of a shift register.
18. The superconducting input/output system of claims 17 wherein the shift register is communicatively coupled to a DAC.
19. The superconducting input/output system of claim 1 further comprising a third interface inductively coupled to the QFP and selectively operable to apply a third flux bias to the QFP.