A quantum device is fabricated by forming a network of nanowires oriented in a plane of a substrate to produce a Majorana-based topological qubit. The nanowires are formed from combinations of selective-area-grown semiconductor material along with regions of a superconducting material. The selective-area-grown semiconductor material is grown by etching trenches to define the nanowires and depositing the semiconductor material in the trenches. A side gate is formed in an etched trench and situated to control a topological segment of the qubit.

Disclosed herein are quantum dot devices, as well as related computing devices and methods. For example, in some embodiments, a quantum dot device may include: a substrate and a quantum well stack disposed on the substrate. The quantum well stack may include a quantum well layer and a back gate, and the back gate may be disposed between the quantum well layer and the substrate.

A silicon-based quantum device is provided. The device comprises: a first metallic structure (501); a second metallic structure (502) laterally separated from the first metallic structure; and an L-shaped elongate channel (520) defined by the separation between the first and second metallic structures; wherein the elongate channel has a vertex (505) connecting two elongate parts of the elongate channel. The device further comprises: a third metallic structure (518), mediator gate, positioned in the elongate channel; a fourth metallic structure (531) forming a first barrier gate, arranged at a first end of the third metallic structure; and a fifth metallic structure (532) forming a second barrier gate arranged at a second end of the third metallic structure. The first, second, third, fourth and fifth metallic structures are configured for connection to first, second, third, fourth and fifth electric potentials respectively. The first, second, fourth and fifth electric potentials are controllable to define an electrical potential well to confine quantum charge carriers in an elongate quantum dot beneath the elongate channel. The fourth and fifth electric potentials and the position of the fourth and fifth metallic structures define first and second ends of the elongate channel respectively. The width of the electrical potential well is defined by the position of the first and second metallic structures and their corresponding electric potentials; and the length of the electrical potential well is defined by the position of the fourth and fifth metallic structures and their corresponding electric potentials. The third electric potential is controllable to adjust quantum charge carrier energy levels in the electrical potential well.

Semiconductor devices includes third arms. A channel from the first and second arms extends to a channel of the third arm. When a current from a first voltage is flowing from the first arm to the second arm, a flow of ballistic electrons is generated that flow through the third arm channel from the channel of the first and second arms to the third arm channel. A fin structure located in the third arm channel and includes a gate. The gate is controlled using a second voltage over the fin structure, the fin structure is formed to induce an energy-field structure that shifts by an amount of the second voltage to control an opening of the gate that the flow of ballistic electrons pass through, which in turn changes a depletion width, subjecting the ballistic electrons to diffraction, and then interference.

Various embodiments of a modular unit for a topologic qubit and of scalable quantum computing architectures using such modular units are disclosed herein. For example, one example embodiment is a modular unit for a topological qubit comprising 6 Majorana zero modes (MZMs) on a mesoscopic superconducting island. These units can provide the computational MZMs with protection from quasiparticle poisoning. Several possible realizations of these modular units are described herein. Also disclosed herein are example designs for scalable quantum computing architectures comprising the modular units together with gates and reference arms (e.g., quantum dots, Majorana wires, etc.) configured to enable joint parity measurements to be performed for various combinations of two or four MZMs associated with one or two modular units, as well as other operations on the states of MZMs.

A parametric amplifier for amplifying an input signal includes a resonator comprising a Josephson junction. The Josephson junction comprises a first superconductor component, a second superconductor component and a semiconductor component. The semiconductor component is configured to enable coupling of the first and second superconductor components. The parametric amplifier further comprises a gate electrode configured to apply an electrostatic field to the semiconductor component of the Josephson junction for tuning the parametric amplifier. Such parametric amplifiers are useful for amplifying signals in the microwave frequency range. Tuning the junction by electrostatic gating may allow for improved scalability compared to tuning using magnetic flux. Also provided are the use of the parametric amplifier to amplify a signal; and a method of amplifying a signal.

Systems and methods for controlling one or more qubits in a quantum processor are disclosed. The system comprises a quantum processor comprising one or more spin-based qubits; and a dielectric resonator positioned in proximity to the quantum processor. The dielectric resonator provides a magnetic field. The quantum processor is positioned in a portion of the magnetic field provided by the resonator such that the portion of the magnetic field controls the spin transitions of the one or more spin-based qubits of the quantum processor.

A quantum computing device is fabricated by forming, on a superconductor layer, a first resist pattern defining a device region and a sensing region within the device region. The superconductor layer within the sensing region is removed, exposing a region of an underlying semiconductor layer outside the device region. The exposed region of the semiconductor layer is implanted, forming an isolation region surrounding the device region. Using an etching process subsequent to the implanting, the sensing region and a portion of the device region of the superconductor layer adjacent to the isolation region are exposed. By depositing a first metal layer within the sensing region, a tunnel junction gate is formed. A reflectrometry wire comprising a second metal within the reflectrometry region is formed. A nanorod contact using the second metal within the portion of the device region outside the sensing region is formed.

The invention relates to a device including a set of superconducting conductors, of junctions and of control elements, each conductor comprising a first portion extending according to a first direction and a set of second portions, the first portions being offset relative to each other according to a second direction, at least three junctions being interposed according to the second direction between each pair of successive first portions, each junction being connected to the first portion of each of the conductors between which the junction is interposed by a second portion of said conductor, each control element being configured to switch the associated junction between a configuration in which the junction forms a Josephson junction and a configuration in which the junction blocks the Cooper pairs.

There is provided a method for fabricating a device. On a top surface of a substrate, a first layer of a first deposition material is formed. The first layer of the first deposition material is patterned to create a seed pattern of remaining first deposition material. Homoepitaxy is used to grow a second layer of the first deposition material on the seed pattern.