A method of fabricating a superconducting-semiconducting stack includes cleaning a surface of a substrate, the substrate comprising a group IV element; depositing an insulating buffer layer onto the substrate, the insulating buffer layer comprising the group IV element; depositing a p-doped layer onto the insulating buffer layer; depositing a diffusion barrier onto the p-doped layer; and processing the superconducting-semiconducting stack through dopant activation.

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.

A method and a system for fabricating superconducting nanowire single photon detector (SNSPD) is disclosed. The superconducting nanowire single photon detector consists of a thin film of superconducting material shaped into a meandering nanowire through nanofabrication processes. The pattern enables the nanowire to cover a wide surface area. The SNSPD is a type of near-infrared single-photon detector based on a current-biased superconducting nanowire. The method includes depositing a plurality of buffer layers on a substrate of a superconducting nanowire single photon detector using a pulsed laser deposition technique. The method further includes designing deposited buffer layer into a desired pattern of nanostrips and depositing a plurality of high temperature superconductor (HTS) on the desired pattern of nanostrips. To obtain the desired pattern, at least one of lithography and/or etching processes is used in the SNSPD.

Systems and techniques providing suitable chip structures for facilitating antenna-based thermal annealing of qubits are provided. In one example, a radio frequency emitter can comprise a voltage-controlled oscillator and an antenna. The voltage-controlled oscillator can receive power-on signals from a microcontroller, thereby causing the voltage-controlled oscillator to generate an electromagnetic wave. The antenna can then direct the electromagnetic wave onto a set of one or more capacitor pads of a Josephson junction on a superconducting qubit chip, thereby annealing the Josephson junction. In another example, a voltage regulator and a digital-to-analog converter or digital-to-digital converter can be coupled in series between the microcontroller and the voltage-controlled oscillator, thereby allowing the voltage-controlled oscillator to be voltage and/or frequency tunable and eliminating the need for external power routing as compared to photonic laser annealing. In yet another example, a bipolar-junction and complementary metal-oxide semiconductor stack construction can be employed.

Techniques and methods to form smooth metal layers deposited onto selected surfaces of Josephson junction devices are provided. For example, one or more embodiments described herein can comprise depositing a layer of a first material comprising metal atom species on a selected surface of a device layer; depositing a layer of a second material on a surface of the layer of first material; and performing plasma etching on the layer of second material and the layer of first material to form an etched surface of the layer of first material that is smoother than the surface of the layer of first material, as deposited.

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.

A method of an embodiment includes forming a capacitor pad for a nonlinear resonator. In an embodiment, the method includes comparing a resonance frequency of the nonlinear resonator to a target frequency to determine whether the resonance frequency falls within a range of the target frequency. A device of an embodiment includes a first capacitor pad comprising a superconducting material, the first capacitor pad configured to couple to a first end of a logic circuit element. In an embodiment, the device includes a second capacitor pad comprising a second superconducting material, the capacitor pad configured to couple to a second end of the logic circuit element. In an embodiment, the second capacitor pad includes a first portion; a second portion; and a bridge configured to electrically connect the first portion and the second portion.

A digital circuit includes at least one quantum wire resonant tunneling transistor that includes an emitter terminal, a base terminal, a collector terminal, an emitter region in connection with the emitter terminal, a base region in connection with the base terminal, a collector region in connection with the collector terminal, an emitter barrier region between the emitter region and the base region, and a collector barrier region between the collector region and the base region. At least one of the emitter region, the base region, and the collector region includes a plurality of metal quantum wires.

Apparatuses and methods are described for laser annealing of a qubit device using a plurality of optical beams. According to an embodiment, a method of tuning a qubit device can comprise generating an optical beam, splitting the optical beam in a plurality of optical beams, and annealing a Josephson junction of the qubit device by projecting the plurality of optical beams onto a region of the qubit device adjacent to the Josephson junction. The disclosed techniques can also be applied for annealing other types of electrical components of various microscale integrated circuit devices.

A method produces a semiconductor apparatus for a quantum computer. The apparatus includes: a semiconductor substrate; a quantum computer device formed on the semiconductor substrate; and a peripheral circuit formed on the semiconductor substrate and connected to the quantum computer device. The apparatus is to be used as a quantum computer. The method includes: a step of forming the quantum computer device and the peripheral circuit on the semiconductor substrate; and a step of deactivating a carrier in the semiconductor substrate by irradiation of a particle beam to at least a formation part for the quantum computer device and a formation part for the peripheral circuit in the semiconductor substrate. The method for producing a semiconductor apparatus for a quantum computer can produce a semiconductor apparatus for a quantum computer having excellent 3HD characteristics.