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.

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.

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.

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.

A manufacturing method includes forming a superconductive thin-film layer on a substrate and processing the superconductive thin-film layer into a shape of a detection coil for magnetic resonance measurement. Accordingly, a superconductive thin-film layer having the detection coil shape can be formed. The method further includes irradiating the shape-processed superconductive thin-film layer with ions. Accordingly, lattice defects serving as pinning can be formed in the superconductive thin-film layer.

Symmetrical qubits with reduced far-field radiation are provided. In one example, a qubit device includes a first group of superconducting capacitor pads positioned about a defined location of the qubit device, wherein the first group of superconducting capacitor pads comprise two or more superconducting capacitor pads having a first polarity, and a second group of superconducting capacitor pads positioned about the defined location of the qubit device in an alternating arrangement with the first group of superconducting capacitor pads, wherein the second group of superconducting capacitor pads comprise two or more superconducting capacitor pads having a second polarity that is opposite the first polarity.

A high temperature superconductor, HTS, tape (100) for detecting a quench in a superconducting magnet. The HTS tape comprises an HTS layer (101) of HTS material supported by a substrate (102). The HTS layer is divided into a plurality of strips (104,105,107). The strips are connected (106) in series along an open path.

Symmetrical qubits with reduced far-field radiation are provided. In one example, a qubit device includes a first group of superconducting capacitor pads positioned about a defined location of the qubit device, wherein the first group of superconducting capacitor pads comprise two or more superconducting capacitor pads having a first polarity, and a second group of superconducting capacitor pads positioned about the defined location of the qubit device in an alternating arrangement with the first group of superconducting capacitor pads, wherein the second group of superconducting capacitor pads comprise two or more superconducting capacitor pads having a second polarity that is opposite the first polarity.

Various fabrication method are disclosed. In one such method, at least one structure is formed on a substrate which protrudes outwardly from a plane of the substrate. A beam is used to form a layer of material, at least part of which is in direct contact with a semiconductor structure on the substrate, the semiconductor structure comprising at least one nanowire. The beam has a non-zero angle of incidence relative to the normal of the plane of the substrate such that the beam is incident on one side of the protruding structure, thereby preventing a portion of the nanowire in a shadow region adjacent the other side of the protruding structure in the plane of the substrate from being covered with the material.

Topological superconductor devices with gates formed in two gate layers are described. A topological superconductor device includes a superconducting wire having a first junction near a first end of the superconducting wire and a second junction near a second end, opposite to the first end. The topological superconductor device further includes: (1) a first side-plunger gate and a second-side plunger gate formed in a first gate layer of the topological superconductor device, (2) a middle-plunger gate formed in the first gate layer of the topological superconductor device, (3) a first cutter gate formed in a second layer, different from the first layer, of the topological superconductor device, and (4) a second cutter gate formed in the second layer of the topological superconductor device. The plunger gates are operable to tune respective sections of the superconducting wire and the cutter gates are operable to open and close the respective junctions.