Metastability-free clockless single flux quantum logic circuitry

A device, comprising:

• a logic circuit comprising a clockless single flux quantum logic gate, wherein the clockless single flux quantum logic gate comprises:
• a first input port, a second input port, and an output port;
• a first dynamic storage loop circuit;
• a second dynamic storage loop circuit;
• an output Josephson junction which is coupled to an output of the first dynamic storage loop circuit and an output of the second dynamic storage loop circuit, and which is configured to drive the output port;
• a first multi-stage Josephson transmission line buffer circuit coupled between the first input port and the first dynamic storage loop circuit, wherein the first multi-stage Josephson transmission line buffer circuit comprises an output stage which comprises a Josephson junction that is configured to absorb a circulating current of an antifluxon without switching, which is injected into the first dynamic storage loop circuit as a result of the output Josephson junction switching to generate a single flux quantum output pulse on the output port, in order to prevent the antifluxon from being output from the first input port, and configured to switch and inject a fluxon into the first dynamic storage loop circuit in response to a single flux quantum pulse applied to the first input port, and annihilate an antifluxon that is present in the first dynamic storage loop circuit;
• and
• a second multi-stage Josephson transmission line buffer circuit coupled between the second input port and the second dynamic storage loop circuit, wherein the second multi-stage Josephson transmission line buffer circuit comprises an output stage which comprises a Josephson junction that is configured to absorb a circulating current of an antifluxon without switching, which is injected into the second dynamic storage loop circuit as a result of the output Josephson junction switching to generate a single flux quantum output pulse on the output port, in order to prevent the antifluxon from being output from the second input port, and configured to switch and inject a fluxon into the second dynamic storage loop circuit in response to a single flux quantum pulse applied to the second input port, and annihilate an antifluxon that is present in the second dynamic storage loop circuit.

A method, comprising:

• receiving a first single flux quantum pulse on a first input port of a clockless single flux quantum logic gate in a given clock cycle;
• injecting a fluxon into a first dynamic storage loop circuit of the clockless single flux quantum logic gate in response to the first single flux quantum pulse;
• outputting a single flux quantum pulse on an output port of the clockless single flux quantum logic gate in response to the fluxon being injected into the first dynamic storage loop circuit;
• injecting an antifluxon into a second dynamic storage loop circuit of the clockless single flux quantum logic gate in response to outputting the single flux quantum pulse on the output port;
• and
• utilizing a Josephson junction of an isolation buffer circuit which is coupled to an input of the second dynamic storage loop circuit, to absorb a circulating current of the antifluxon without switching, to prevent the antifluxon from being output from a second input port of the clockless single flux quantum logic gate.