Superconducting output amplifier having return to zero to non-return to zero converters

A method for a superconducting output amplifier comprising a plurality of superconducting output amplifier (OA) stages, wherein the superconducting output amplifier comprises an input terminal, a positive output voltage terminal, and a negative output voltage terminal, the method comprising:

• receiving via the input terminal a pulse train comprising a plurality of single flux quantum (SFQ) pulses;
• processing the pulse train to generate a first set of return to zero (RZ) signals and a second set of RZ signals;
• using a first set of return to zero to non-return to zero (RZ-NRZ) converters, converting the first set of RZ signals into a first set of non-return to zero (NRZ) signals for driving a first set of direct current-superconducting quantum interference devices (DC-SQUIDS) associated with the plurality of superconducting OA stages, wherein each of the first set of DC-SQUIDS is associated with a first compound DC-SQUID;
• using a second set of RZ-NRZ converters, converting the second set of RZ signals into a second set of NRZ signals for driving a second set of DC-SQUIDs associated with the plurality of superconducting OA stages, wherein each of the second set of DC-SQUIDS is associated with a second compound DC-SQUID, and wherein the first set of DC-SQUIDS associated with the first compound DC-SQUID and the second set of DC-SQUIDs associated with the second compound DC-SQUID are configured to be active at the same time when, respectively, providing a positive output voltage at the positive output voltage terminal of the superconducting output amplifier and providing a negative output voltage at the negative output voltage terminal of the superconducting output amplifier;
• and
• using the stack of the plurality of superconducting OA stages, converting the first set of NRZ signals and the second set of NRZ signals into an output voltage waveform representative of a differential between the positive output voltage at the positive output voltage terminal and the negative output voltage at the negative output voltage terminal.

A superconducting output amplifier comprising:

• a first superconducting output amplifier (OA) stage having a first direct current-superconducting quantum interference device (DC-SQUID) and a second DC-SQUID arranged in parallel to the first DC-SQUID, wherein the first DC-SQUID and the second DC-SQUID are coupled via an inductor forming a compound DC-SQUID;
• an input terminal of the first superconducting OA stage for receiving a single flux quantum (SFQ) pulse train comprising a plurality of SFQ pulses, wherein the SFQ pulse train comprises data corresponding to reciprocal quantum logic return to zero encoding or data corresponding to phase-mode logic encoding;
• a positive output voltage terminal of the compound DC-SQUID for outputting a positive output voltage in response to the SFQ pulse train;
• a negative output voltage terminal of the compound DC-SQUID for outputting a negative output voltage in response to the same SFQ pulse train;
• a first splitter configured to split a first set of SFQ pulses corresponding to the SFQ pulse train into a first return to zero (RZ) signal and a second RZ signal;
• and
• a first return to zero to non-return to zero (RZ-NRZ) converter configured to convert the first RZ signal into a first non-return to zero (NRZ) signal for driving the first DC-SQUID, and a second RZ-NRZ converter configured to convert the second RZ signal into a second NRZ signal for driving the second DC-SQUID, wherein the first DC-SQUID and the second DC-SQUID associated with the compound DC-SQUID are configured to be active at the same time when, respectively, generating the positive output voltage terminal at the positive output voltage terminal of the compound DC-SQUID and the negative output voltage at the negative output voltage terminal of the compound DC-SQUID in response to currents generated by the first RZ signal and the second RZ signal based on the same SFQ pulse train received via the input terminal of the first superconducting QA stage.