The invention is notably directed to a method of operating a superconducting channel. The method relies on a device including: a potentially superconducting material; a gate electrode; and an electrically insulating medium. A channel is defined by the potentially superconducting material. The gate electrode positioned adjacent to the channel, such that an end surface of the gate electrode faces a portion of the channel. The electrically insulating medium is arranged in such a manner that it electrically insulates the gate electrode from the channel. Rendering the channel superconducting by cooling down the device. Next, a voltage difference is applied between the gate electrode and the channel to inject electrons in the channel through the electrically insulating medium and thereby generate a gate current between the gate electrode and the channel. The electrons are injected with an average energy sufficient to modify a critical current I.sub.C of the channel.

The various embodiments described herein include methods, devices, and systems for fabricating and operating superconducting circuits. In one aspect, an electric circuit includes: (1) a first superconducting component having a first terminal, a second terminal, and a constriction region between the first terminal and the second terminal; (2) a second superconducting component having a third terminal and a fourth terminal; and (3) a first electrically-insulating component that thermally couples the first superconducting component and the second superconducting component such that heat produced at the constriction region is transferred through the first component to the second superconducting component.

A device that is a combination of a superconducting nanowire single-photon detector and a superconducting multi-level memory. These devices can be used to count a number of photons impinging on the device through single-photon to single-flux conversion. Electrical characterization of the device demonstrates single-flux quantum (SFQ) separated states. Optical measurements using attenuated laser pulses with different mean photon number, pulse energies and repetition rates are shown to differentiate single-photon detection from other possible phenomena, such as multiphoton detection and thermal activation. Array devices and methods are also discussed.

An active cooling structure, comprising a non-superconducting layer, a superconducting layer, and an array of Superconductor-Insulator-Normal Metal (NIS) tunnel junctions. The non-superconducting layer may comprise a plurality of non-superconducting traces. The superconducting layer may comprise a plurality of superconducting traces. The array of Superconductor-Insulator-Normal Metal (NIS) tunnel junctions may be located between the plurality of non-superconducting traces and the plurality of superconducting traces.

A bistable device allows supercurrent to flow when functioning in one regime, wherein magnetization directions of different magnetic layers are antiparallel, but restricts supercurrent when switched to function in a resistive regime, wherein the magnetization directions are parallel. In the first regime, the device acts as a Josephson junction, which allows it to be used in superconducting quantum interference devices (SQUIDs) and other circuits in which quantization of magnetic flux in a superconducting loop is desired. In the second, resistive regime, flux quantization is effectively eliminated in loops containing the device, and current is diverted to parallel superconducting components. The bistable device thereby acts as a superconducting switch, useful for a variety of circuit applications, including to steer current for memory or logic circuits, adjust logical circuit functionality at runtime, or to burn off stray flux during cooldown.

A solid state cooler device is disclosed that includes a first superconductor shunt, a first normal metal pad disposed on the first superconductor shunt, and a first insulator layer and a second insulator layer disposed on the normal metal pad and separated from one another by a gap. The solid state cooler device also includes a first superconductor pad disposed on the first insulator layer and a second superconductor pad disposed on the second insulator layer, a first conductive pad coupled to the first superconductor pad, and a second conductive pad coupled to the second superconductor pad. Hot electrons are removed from the first normal metal pad when a bias voltage is applied between the first conductive pad and the second conductive pad, wherein the first superconductor shunt facilitates even current distribution through the device.

A device that is a combination of a superconducting nanowire single-photon detector and a superconducting multi-level memory. These devices can be used to count a number of photons impinging on the device through single-photon to single-flux conversion. Electrical characterization of the device demonstrates single-flux quantum (SFQ) separated states. Optical measurements using attenuated laser pulses with different mean photon number, pulse energies and repetition rates are shown to differentiate single-photon detection from other possible phenomena, such as multiphoton detection and thermal activation. Array devices and methods are also discussed.

A bundle of superconducting cables employs a plurality of superconducting cables, each having a former and a plurality of superconducting tape conductors wound in at least one layer around the former in a helical fashion. Each superconducting tape conductor has at least one superconducting layer. Each superconducting cable lacks an outer insulating layer and is held in a bundle of cables with each other superconducting cable of the plurality of superconducting cables. A sheath of non-conductive material covers the bundle of cables.

A photon source includes a photo-pair generator and a detection device. The photo-pair generator is configured to generate a photon-pair in receiving an input signal. A first photon of the photon-pair is output from the photon source via a first optical path. The detection device is configured to receive a second photon of the photon-pair. The detection device includes a transistor that has a semiconducting component that is a source and a drain of the transistor, and a superconducting component that is adjacent to the semiconducting component and is a gate of the transistor. The transistor is configured to transition from an off state to an on state in response a photon being incident upon the detection device.

Superconducting switch having a persistent and a non-persistent state and its use as a driver in a memory system are described. An example superconducting switch includes a first superconducting layer and a second superconducting layer. The superconducting switch includes a first magnetic layer having a fixed magnetization state. The superconducting switch includes a second magnetic layer capable of being at least in a first or a second magnetization state. The superconducting switch is capable of being in a first state or a second state, and the superconducting switch is configured such that an application of a magnetic field to the second magnetic layer changes a magnetization of the second magnetic layer from the first magnetization state to the second magnetization state placing the superconducting switch in the second state and a removal of the magnetic field automatically returns the superconducting switch from the second state to the first state.