Superconducting three-terminal device and logic gates
AssigneeMassachusetts Institute of Technology
InventorsAdam N. McCaughan, Karl K. Berggren
Life of this patent
Estimating the term…
Abstract
A three-terminal device that exhibits transistor-like functionality at cryogenic temperatures may be formed from a single layer of superconducting material. A main current-carrying channel of the device may be toggled between superconducting and normal conduction states by applying a control signal to a control terminal of the device. Critical-current suppression and device geometry are used to propagate a normal-conduction hotspot from a gate constriction across and along a portion of the main current-carrying channel. The three-terminal device may be used in various superconducting signal-processing circuitry.
Claims25
A three-terminal device comprising:
- a main channel connecting a first terminal and a second terminal;
- a gate channel connecting a control terminal to the main channel;
- and
- a low-resistance constriction formed in the gate channel between the control terminal and the main channel, wherein the constriction is configured to increase a gate current density proximal to the main channel and the constriction is located within approximately 200 nm of an edge of the main channel.
A three-terminal device comprising:
- a main channel connecting a first terminal and a second terminal;
- a gate channel connecting a control terminal to the main channel;
- and
- a low-resistance constriction formed in the gate channel between the control terminal and the main channel, wherein the constriction is configured to increase a gate current density proximal to the main channel, wherein the constriction is located within approximately two diffusion lengths of a far edge of the main channel at an intersection with the gate channel, wherein one diffusion length LD is given by the following expression
- LD=√{square root over (Deτr)}
- where De is the diffusion constant for electrons in a superconducting material from which the gate channel is formed and τr is the recombination time for hot electrons in the superconducting material in a superconducting state.
A three-terminal device comprising:
- a main channel connecting a first terminal and a second terminal;
- a gate channel connecting a control terminal to the main channel;
- a low-resistance constriction formed in the gate channel between the control terminal and the main channel, wherein the constriction is configured to increase a gate current density proximal to the main channel;
- and
- periodic width modulations formed in the main channel and located near a junction of the gate channel with the main channel.
A method of operating a three-terminal device fabricated from a superconducting material, the method comprising:
- placing the three-terminal device in a superconducting state, such that a main channel between a first terminal and a second terminal is superconducting;
- applying a control signal to a constriction in a gate channel that connects a control input to the main channel, such that current at the constriction exceeds a superconducting critical current level at the constriction;
- propagating a normal-conduction hotspot that suppresses a superconducting critical current value from the constriction to the main channel;
- and
- forming a stable resistive plug in the main channel.
A multi-input OR gate comprising:
- a main channel connecting a first terminal and a second terminal;
- at least two gate channels connecting at least two control terminals to the main channel;
- and
- at least two low-resistance constrictions formed in the at least two gate channels between the at least two control terminals and the main channel, wherein each constriction is configured to increase a gate current density proximal to the main channel, wherein the constrictions are located within approximately two diffusion lengths of a far edge of the main channel at each intersection with each gate channel, wherein one diffusion length LD is given by the following expression
- LD=√{square root over (Deτr)}
- where De is the diffusion constant for electrons in a superconducting material from which the gate channel is formed and τr is the recombination time for hot electrons in the superconducting material in a superconducting state.
Dependencies are inferred from the claim text.