The present disclosure provides a superconducting qubit. The superconducting qubit includes: a Josephson junction and a non-Josephson junction area, wherein the non-Josephson junction area includes a first layer of superconducting material, the first layer of superconducting material being superconducting material deposited on the non-Josephson junction area before ion milling on the Josephson junction and the non-Josephson junction area during preparation of the superconducting qubit.

A mixed semiconductor-superconductor platform is fabricated in phases. In a masking phase, a dielectric mask is formed on a substrate, such that the dielectric mask leaves one or more regions of the substrate exposed. In a selective area growth phase, a semiconductor material is selectively grown on the substrate in the one or more exposed regions. In a superconductor growth phase, a layer of superconducting material is formed, at least part of which is in direct contact with the selectively grown semiconductor material. The mixed semiconductor-superconductor platform comprises the selectively grown semiconductor material and the superconducting material in direct contact with the selectively grown semiconductor material.

The present invention relates to a phononic-isolated Kinetic Inductance Detector (KID) and a method of fabrication thereof. The KID is a highly sensitive superconducting cryogenic detector which can be scaled to very large format arrays. The fabrication process of the KID of the present invention integrates a phononic crystal into a KID architecture. The phononic structures are designed to reduce the loss of recombination and athermal phonons, resulting in lower noise and higher sensitivity detectors.

A method of producing a quantum circuit includes forming a mask on a substrate to cover a first portion of the substrate, implanting a second portion of the substrate with ions, and removing the mask, thereby providing a nanowire. The method further includes forming a first lead and a second lead, the first lead and the second lead each partially overlapping the nanowire. In operation, a portion of the nanowire between the first and second leads forms a quantum dot, thereby providing a quantum dot Josephson junction. The method further includes forming a third lead and a fourth lead, one of the third and fourth leads partially overlapping the nanowire, wherein the third lead is separated from the fourth lead by a dielectric layer, thereby providing a Dolan bridge Josephson junction. The nanowire is configured to connect the quantum dot Josephson junction and the Dolan bridge Josephson junction in series.

Certain embodiments involve processes or systems for creating various high-temperature superconductive structures or materials. For example, a method can involve depositing a first layer of boron and a second layer of un-doped amorphous carbon on a substrate. The un-doped amorphous carbon is ferromagnetic. The first layer of boron and the second layer of un-doped amorphous carbon are melted by a laser pulse to form a melted boron-doped amorphous carbon. The melted boron-doped amorphous carbon is quenched to create a quenched boron-doped amorphous carbon that is diamagnetic and superconducting. The quenched melted boron-doped amorphous carbon includes a mixture of sp3 bonded carbon atoms and sp2 bonded carbon atoms and a superconducting transition temperature of the quenched boron-doped amorphous carbon is much higher than diamond and increases based on a boron concentration. Undoped Q-carbon is ferromagnetic with Curie temperature above 500K.

A superconductor having improved critical current density when exposed to high-energy neutron radiation and high magnetic fields, such as found in a compact nuclear fusion reactor, and a method of making the same are described. According to some aspects, the method includes, prior to deployment in the exposure environment, irradiating a polycrystalline superconductor with ions and/or neutrons at a cryogenic temperature to create “weak” magnetic flux pinning sites, such as point defects or small defect clusters. Irradiation temperature is chosen, for example as a function of the superconducting material, so that irradiation creates the beneficial flux pinning sites while avoiding detrimental widening of the boundaries of the crystalline grains caused by diffusion of the displaced atoms. Such a superconductor in a coated-conductor tape is expected to be beneficial when used as a toroidal field coil in a fusion reactor when cooled well below its critical temperature.

Disclosed are a superconductor having improved critical current density when exposed to high-energy neutron radiation and high magnetic fields, such as found in a compact nuclear fusion reactor, and a method of making the same. The method includes, prior to deployment in the exposure environment, irradiating a polycrystalline (e.g. cuprate) superconductor with ionic matter or neutrons at a cryogenic temperature to create “weak” magnetic flux pinning sites, such as point defects or small defect clusters. Irradiation temperature is chosen, for example as a function of the superconducting material, so that irradiation creates the beneficial flux pinning sites while avoiding detrimental widening of the boundaries of the crystalline grains caused by diffusion of the displaced atoms. Such a superconductor in a coated-conductor tape is expected to be beneficial when used, for example, as a toroidal field coil in a fusion reactor when cooled well below its critical temperature.

Compositions of matter and methods of identifying and making compositions of matter are disclosed. Some embodiments disclose making and chemically and/or compositionally tuning superconducting hydride materials. Some embodiments disclose an apparatus for making and compositionally tuning superconducting materials. Some embodiments disclose a composition of matter including a solid hydride exhibiting superconductivity at a temperature of at least 150 kelvin at an ambient pressure below 180 gigapascals, or at a temperature of at least 261 kelvin. In one or more embodiments, the superconductor includes a covalent metal hydride having at least three different chemical elements wherein an inter-atomic distance between the hydrogen in the covalent metal hydride is in a range of 1.1-2 angstroms. In yet further examples, the superconductor is formed using molecular exchange and compression of a Van der Waals solid. In yet further examples, the superconductor comprises molecular hydrogen disposed in 1-dimensional channels. These and other embodiments are disclosed herein.

Systems and techniques facilitating antenna-based thermal annealing of qubits are provided. In one example, a radio frequency emitter, transmitter, and/or antenna can be positioned above a superconducting qubit chip having a Josephson junction coupled to a set of one or more capacitor pads. The radio frequency emitter, transmitter, and/or antenna can emit an electromagnetic signal onto the set of one or more capacitor pads. The capacitor pads can function as receiving antennas and therefore receive the electromagnetic signal. Upon receipt of the electromagnetic signal, an alternating current and/or voltage can be induced in the capacitor pads, which current and/or voltage thereby heat the pads and the Josephson junction. The heating of the Josephson junction can change its physical properties, thereby annealing the Josephson junction. In another example, the emitter can direct the electromagnetic signal to avoid unwanted annealing of neighboring qubits on the superconducting qubit chip.

Provided are a solar cell having a good conversion efficiency in which damage to a p-n junction structure is prevented when an antireflection film is removed, and a method of manufacturing such a solar cell.