Abstract: Current-based superconductor memory cell and related systems and methods are provided. A method in a memory system, having at least one storage circuit and at least one read SQUID, includes applying bit-line current, via a read bit-line not including any Josephson transmission line (JTL) elements, to the at least one read SQUID. The method further includes applying word-line current, via a read word-line not including any JTL elements, to the at least one read SQUID. The method further includes using the at least one read SQUID reading a logic state of the memory cell based on data maintained in the storage circuit.

Abstract: One embodiment includes a clock distribution system. The system includes a standing-wave resonator configured to receive and to resonate a sinusoidal clock signal. The standing-wave resonator includes at least one anti-node portion associated with a peak current amplitude of the sinusoidal clock signal. The system also includes at least one clock line interconnecting each of the at least one anti-node portion and an associated circuit. The at least one clock line can be configured to propagate the sinusoidal clock signal for timing functions associated with the associated circuit.

Abstract: Current-based superconductor memory cell and related systems and methods are provided. A method in a memory system, having at least one storage circuit and at least one read SQUID, includes applying bit-line current, via a read bit-line not including any Josephson transmission line (JTL) elements, to the at least one read SQUID. The method further includes applying word-line current, via a read word-line not including any JTL elements, to the at least one read SQUID. The method further includes using the at least one read SQUID reading a logic state of the memory cell based on data maintained in the storage circuit.

Abstract: Output amplifier comprising a stack of compound superconducting quantum interference device (SQUID) output amplifier stages and related methods are provided. A method includes receiving a first pulse train comprising a first plurality of single flux quantum (SFQ) pulses. The method may further include receiving a second pulse train comprising a second plurality of SFQ pulses, where the second pulse train is delayed by a predetermined fraction of a clock cycle relative to the first pulse train. The method may further include using the stack of the plurality of compound SQUID output amplifier stages converting the first plurality of SFQ pulses and the second plurality of SFQ pulses into a voltage waveform, where each of the plurality of compound SQUID output amplifier stages comprises a pair of superconducting quantum interference devices (SQUIDs).

Abstract: The circuit includes a memory array arranged as rows and columns of memory cells. An array portion stores a respective memory word in a given one of the rows in response to a word-write signal corresponding to a write address of the given one of the rows and in response to a plurality of bit-write signals associated with the plurality of columns, and reads a respective memory word from a given one of the rows in response to a word-read signal corresponding to a read address of the given one of the rows and in response to a plurality of bit-read signals associated with the plurality of columns. The circuit also includes a write-through detection system that activates an analog bypass portion to read the memory word from the analog bypass portion in response to the read address being the same as the write address.

Abstract: Superconducting circuits based devices and methods, including reciprocal quantum logic (RQL) based devices and methods are provided. In one example, a device comprising an output terminal, a first input terminal for receiving a first set of pulses, and a second input terminal for receiving a second set of pulses is provided. The first section may be configured to pass a single pulse received during a single clock cycle at any of the first input terminal or the second input terminal, but to not pass two or more positive pulses received during a single clock cycle at the first input terminal and the second input terminal. The second section, coupled to the first section, may be configured to, in response to the single pulse, generate a negative pulse after a predetermined fraction of a single clock cycle after providing a positive pulse at the output terminal.

Abstract: A Josephson inverter gate circuit provides efficient implementation of polarity or logical inversion while eliminating the need for physically large high-efficiency magnetic transformers in the signal path. The circuit can consist of a half-twisted Josephson transmission line (JTL) or a JTL with an unshunted floating Josephson junction that produces two single flux quantum (SFQ) pulses when triggered by an SFQ input signal, which results in an output SFQ signal of reversed polarity. Implemented as a logical inverter, proper initialization of the circuit is accomplished within the signal inversion stage with flux biasing.

Abstract: One embodiment describes a Josephson current source system comprising a flux-shuttle loop that is inductively coupled with an AC input signal. The flux-shuttle loop includes a plurality of stages each comprising at least one Josephson junction. The plurality of stages can be spaced about the flux shuttle loop. Each of a plurality of pairs of the plurality of stages are configured to concurrently trigger in a sequence via the respective at least one Josephson junction in response to the AC input signal and to provide a respective pair of single-flux quantum (SFQ) pulses that move sequentially and continuously through each stage of the plurality of stages around the flux-shuttle loop via each of the at least one Josephson junction of each of the respective stages that results in a DC output current being provided through an output inductor.

Abstract: One example includes a current driver system. The system includes a current source configured to provide a source current to a transition node. The system also includes a Josephson latch comprising at least one Josephson junction stage. The at least one Josephson junction stage can be configured to conduct the source current from the transition node as a current-clamped bias current in a deactivated state of the Josephson latch. The Josephson latch can be configured to activate in response to the bias current and a trigger pulse to switch the at least one Josephson junction stage to a voltage state to conduct at least a portion of the source current from the transition node as an output current to a load in response to activation of the Josephson latch.

Abstract: A Josephson inverter gate circuit provides efficient implementation of polarity or logical inversion while eliminating the need for physically large high-efficiency magnetic transformers in the signal path. The circuit can consist of a half-twisted Josephson transmission line (JTL) or a JTL with an unshunted floating Josephson junction that produces two single flux quantum (SFQ) pulses when triggered by an SFQ input signal, which results in an output SFQ signal of reversed polarity. Implemented as a logical inverter, proper initialization of the circuit is accomplished within the signal inversion stage with flux biasing.

Abstract: One example includes a memory circuit. The circuit includes a memory array arranged as rows and columns of memory cells. An array portion stores a respective memory word in a given one of the rows in response to a word-write signal corresponding to a write address of the given one of the rows and in response to a plurality of bit-write signals associated with the plurality of columns, and reads a respective memory word from a given one of the rows in response to a word-read signal corresponding to a read address of the given one of the rows and in response to a plurality of bit-read signals associated with the plurality of columns. The circuit also includes a write-through detection system that activates an analog bypass portion to read the memory word from the analog bypass portion in response to the read address being equal to the write address.

Abstract: Superconducting interface circuits and methods convert between non-return-to-zero (NRZ) encoded voltage signals and reciprocal quantum logic (RQL) compliant signals of opposite-polarity single flux quantum (SFQ) pulse pairs, and vice-versa, so as to provide high-speed NRZ input to, and output from, RQL computing circuitry.

Abstract: One example includes a superconducting transmission driver system. The system includes a latching gate stage comprising at least one Josephson junction configured to switch from an off state to an oscillating voltage state to provide an oscillating voltage at a control node in response to a single flux quantum (SFQ) pulse received at an input. The system further includes a low-pass filter stage coupled to the control node and configured to convert the oscillating voltage to a pulse signal to be transmitted over a transmission line.

Abstract: A memory system including an array of memory cells may include a set of word-lines, and a set of return word-lines coupled to the memory cells in the array of memory cells. The memory system may further include a set of bit-lines coupled to the memory cells. Each of the memory cells may include a memory storage element including a readout superconducting quantum interference device (SQUID), and a magnetic Josephson Junction (MJJ), and where the memory storage element may further include a differential transformer coupled in series with the MJJ such that in response to a bit-line current applied to at least one of the set of the bit-lines and a word-line current applied to at least one of the set of word-lines, the differential transformer is configured to induce a flux in the at least one readout SQUID.

Abstract: One example includes a current driver system. The system includes a current source configured to provide a source current to a transition node. The system also includes a Josephson latch comprising at least one Josephson junction stage. The at least one Josephson junction stage can be configured to conduct the source current from the transition node as a current-clamped bias current in a deactivated state of the Josephson latch. The Josephson latch can be configured to activate in response to the bias current and a trigger pulse to switch the at least one Josephson junction stage to a voltage state to conduct at least a portion of the source current from the transition node as an output current to a load in response to activation of the Josephson latch.

Abstract: One embodiment includes a superconducting gate memory circuit. The circuit includes a Josephson D-gate circuit configured to set a digital state as one of a first data state and a second data state in response to a write enable single flux quantum (SFQ) pulse provided on a write enable input and a respective presence of or absence of a write data SFQ pulse provided on a data write input. The circuit also includes a storage loop coupled to the Josephson D-gate. The storage loop can be configured to store the digital state and to readout the digital state at an output in response to a read enable SFQ pulse provided on a read enable input and a read data SFQ pulse provided on a read data input.

Abstract: One example includes a superconducting gate system. The system includes a first input that is configured to provide a first input pulse and a second input that is configured to provide a second input pulse. The system also includes a gate configured to provide a first output pulse at a first output corresponding to a first logic function with respect to the first and second input pulses and based on a positive bias inductor and a first Josephson junction that are each coupled to the first output. The gate is also configured to provide a second output pulse at a second output corresponding to a second logic function with respect to the first and second input pulses and based on a negative bias inductor and a second Josephson junction that are each coupled to the second output.

Abstract: A Josephson inverter gate circuit provides efficient implementation of polarity or logical inversion while eliminating the need for physically large high-efficiency magnetic transformers in the signal path. The circuit can consist of a half-twisted Josephson transmission line (JTL) or a JTL with an unshunted floating Josephson junction that produces two single flux quantum (SFQ) pulses when triggered by an SFQ input signal, which results in an output SFQ signal of reversed polarity. Implemented as a logical inverter, proper initialization of the circuit is accomplished within the signal inversion stage with flux biasing.

Abstract: Superconducting circuits based devices and methods, including reciprocal quantum logic (RQL) based devices and methods are provided. In one example, a device comprising an output terminal, a first input terminal for receiving a first set of pulses, and a second input terminal for receiving a second set of pulses is provided. The first section may be configured to pass a single pulse received during a single clock cycle at any of the first input terminal or the second input terminal, but to not pass two or more positive pulses received during a single clock cycle at the first input terminal and the second input terminal. The second section, coupled to the first section, may be configured to, in response to the single pulse, generate a negative pulse after a predetermined fraction of a single clock cycle after providing a positive pulse at the output terminal.

Abstract: One example includes a superconducting transmission driver system. The system includes a latching gate stage comprising at least one Josephson junction configured to switch from an off state to an oscillating voltage state to provide an oscillating voltage at a control node in response to a single flux quantum (SFQ) pulse received at an input. The system further includes a low-pass filter stage coupled to the control node and configured to convert the oscillating voltage to a pulse signal to be transmitted over a transmission line.