A superconducting circuit includes a photon detector component, a second component, and a multi-taper superconducting connector shaped to reduce current crowding, the superconducting connector electrically connecting the photon detector component and the second component. The multi-taper superconducting connector includes a first taper arranged adjacent the photon detector component and a second taper arranged adjacent the second component.

Various techniques and apparatus permit fabrication of superconductive circuits. A niobium/aluminum oxide/niobium trilayer may be formed and individual Josephson Junctions (JJs) formed. A protective cap may protect a JJ during fabrication. A hybrid dielectric may be formed. A superconductive integrated circuit may be formed using a subtractive patterning and/or additive patterning. A superconducting metal layer may be deposited by electroplating and/or polished by chemical-mechanical planarization. The thickness of an inner layer dielectric may be controlled by a deposition process. A substrate may include a base of silicon and top layer including aluminum oxide. Depositing of superconducting metal layer may be stopped or paused to allow cooling before completion. Multiple layers may be aligned by patterning an alignment marker in a superconducting metal layer.

Various embodiments described herein provide for a topological quantum computer that uses edge Majorana quasi-particles to form qubits. An inverted Indium Arsenide (InAs) and Gallium Antimonide (GaSb) heterostructure is disclosed that is a quantum spin Hall insulator. A layer of aluminum can be deposited over a nanotube that is placed across the layers of the heterostructure. Once the nanotube is removed, and a gate is formed on the heterostructure and the heterostructure is cooled so that the aluminum becomes superconducting, helical edge states are formed at the junction of the super conducting aluminum, the InAs, and the GaSb which creates a Majorana zero modes (MZMs) at zero magnetic field. The MZMs can be used to construct a topological qubit for fault-resistant topological quantum computation.

Operational characteristics of an extremely low resistance (ELR) film comprised of an ELR material may be improved by depositing a modifying material onto appropriate surfaces of the ELR film to create a modified ELR film. In some implementations of the invention, the ELR film may be in the form of a c-film. In some implementations of the invention, the ELR film may be in the form of an a-b film, an a-film or a b-film. The modified ELR film has improved operational characteristics over the ELR film alone or without the modifying material. Such operational characteristics may include operating in an ELR state at increased temperatures, carrying additional electrical charge, operating with improved magnetic properties, operating with improved mechanic properties or other improved operational characteristics. In some implementations of the invention, the ELR material is a mixed-valence copper-oxide perovskite, such as, but not limited to YBCO. In some implementations of the invention, the modifying material is a conductive material that bonds easily to oxygen, such as, but not limited to, chromium.

Described herein are structures that include Josephson Junctions (JJs) to be used in superconducting qubits of quantum circuits disposed on a substrate. The JJs of these structures are fabricated using an approach that allows a wide selection of suitable materials for use in JJs and that can be efficiently used in large scale manufacturing. Thus, proposed fabrication techniques provide a substantial improvement with respect to conventional approaches, such as e.g. double-angle shadow evaporation approach, which are limited in their choice of materials and include fabrications steps that are not manufacturable at the larger wafer sizes used by leading edge device manufactures. In one aspect of the present disclosure, resulting Josephson Junctions may include base and/or top electrodes made from refractory and/or noble metals. Furthermore, tunnel barrier layers of such Josephson Junctions are not limited to oxides of the electrode materials.

The present disclosure relates to nanoscale device comprising an elongated crystalline nanostructure, such as a nanowire crystal, a nanowhisker crystal or a nanorod crystal, and a method for producing thereof. One embodiment relates to a nanoscale device comprising an elongated crystalline semiconductor nanostructure, such as a nanowire (crystal) or nanowhisker (crystal) or nanorod (crystal), having a plurality of substantially plane side facets, a crystalline structured first facet layer of a superconductor material covering at least a part of one or more of said side facets, and a second facet layer of a superconductor material covering at least a part of the first facet layer, the superconductor material of the second facet layer being different from the superconductor material of the first facet layer, wherein the crystalline structure of the semiconductor nanostructure is epitaxially matched with the crystalline structure of the first facet layer on the interface between the two crystalline structures.

A qubit coupling device includes: a dielectric substrate including a trench; a first superconductor layer on a surface of the dielectric substrate where an edge of the first superconductor layer extends along a first direction and at least a portion of the superconductor layer is in contact with the surface of the dielectric substrate, and where the superconductor layer is formed from a superconductor material exhibiting superconductor properties at or below a corresponding critical temperature; a length of the trench within the dielectric substrate is adjacent to and extends along an edge of the first superconductor layer in the first direction, and where the electric permittivity of the trench is less than the electric permittivity of the dielectric substrate.

Disclosed herein is a rare-earth oxide coating on a surface of an article with one or more interruption layers to control crystal growth and methods of its formation. The coating may be deposited by atomic layer deposition and/or by chemical vapor deposition. The rare-earth oxides in the coatings disclosed herein may have an atomic crystalline phase that is different from the atomic crystalline phase or the amorphous phase of the one or more interruption layers.

Disclosed herein is a rare-earth oxide coating on a surface of an article with one or more interruption layers to control crystal growth and methods of its formation. The coating may be deposited by atomic layer deposition and/or by chemical vapor deposition. The rare-earth oxides in the coatings disclosed herein may have an atomic crystalline phase that is different from the atomic crystalline phase or the amorphous phase of the one or more interruption layers.

The present disclosure relates to semiconductor based Josephson junctions and their applications within the field of quantum computing, in particular a tuneable Josephson junction device has been used to construct a gateable transmon qubit. One embodiment relates to a Josephson junction comprising an elongated hybrid nanostructure comprising superconductor and semiconductor materials and a weak link, wherein the weak link is formed by a semiconductor segment of the elongated hybrid nanostructure wherein the superconductor material has been removed to provide a semiconductor weak link.