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.

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.

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.

A particle detector according to one embodiment includes: superconductive lines, conductive lines, insulating films, a first detection circuit, and a second detection circuit. The superconductive lines extend in a first direction and are arranged in a second direction intersecting the first direction. The conductive lines extend in a third direction different from the first direction and are arranged in a fourth direction intersecting the third direction. The insulating films are each interposed at an intersection point between one of the superconductive lines and one of the conductive lines. The first detection circuit detects a voltage change occurring in the superconductive lines. The second detection circuit detects a current or a voltage generated in the conductive lines when the voltage change occurs.

Methods and systems are described for readout of one or more spin states associated with one or more quantum dots in an array of quantum dots, wherein the method comprises: configuring or providing one or more read-out paths of connected quantum dots in the array of quantum dots, the quantum dots of at least one of the one or more read-out paths being configured close to a charge transition point such that a charge transition in one or more first quantum dots at a first end of the tuned read-out path induces a charge transition in one or more second quantum dots at a second end of the tuned read-out path, the second end being connected to a charge detector; configuring one or more quantum dots of the quantum dot array into a spin-to-charge conversion system connected to the first end of the tuned read-out path, the charge convention system including at least two connected quantum dots hosting a spin state or a quantum dot hosting a spin state connected to a reservoir; and, obtaining information about the spin state in the spin-to-charge system, the obtaining information including the charge detector measuring a charge transition in the one or more second quantum dots at a second end of the tuned read-out path.

A novel and useful modified semiconductor fabrication technique for realizing reliable semiconductor quantum structures. Quantum structures require a minimization of the parasitic capacitance of the control gate and the quantum well. The modified semiconductor process eliminates the fabrication of the metal, contact, and optionally the raised diffusion layers from the quantum wells, thereby resulting in much lower well and gate capacitances and therefore larger Coulomb blockade voltages. This allows easier implementation of the electronic control circuits in that they can have larger intrinsic noise and relaxed analog resolution. Several processes are disclosed including implementations of semiconductor quantum structures with tunneling through an oxide layer as well as tunneling through a local well depleted region. These techniques can be used in both planar semiconductor processes and 3D, e.g., FinFET, semiconductor processes. A dedicated process masking step is used for realizing the raised diffusions. In addition, the edge of the raised diffusion layer may be placed either in the gate region or the active layer region.

A method for processing a semiconductor device with two closely space gates comprises forming a template structure, wherein the template structure includes at least one sub-structure having a dimension less than the CD. The method further comprises forming a gate layer on and around the template structure. Then, the method comprises removing the part of the gate layer formed on the template structure, and patterning the remaining gate layer into a gate structure including the two gates. Further, the method comprises selectively removing the template structure, wherein the spacing between the two gates is formed by the removed sub-structure.

A solid state cooler device is disclosed that comprises a first normal metal pad, a first aluminum layer and a second aluminum layer disposed on the first normal metal pad and separated from one another by a gap, a first aluminum oxide layer formed on the first aluminum layer, and a second aluminum oxide layer formed on the second aluminum layer, and a first superconductor pad disposed on the first aluminum oxide layer and a second superconductor pad disposed on the second aluminum oxide layer. The device further comprises a first conductive pad coupled to the first superconductor pad, and a second conductive pad coupled to the second superconductor pad, wherein hot electrons are removed from the first normal metal pad when a bias voltage is applied between the first conductive pad and the second conductive pad.

Devices, systems, methods, computer-implemented methods, apparatus, and/or computer program products that can facilitate an epitaxial Josephson junction transmon device are provided. According to an embodiment, a device can comprise a substrate. The device can further comprise an epitaxial Josephson junction transmon device coupled to the substrate. According to an embodiment, a device can comprise an epitaxial Josephson junction transmon device coupled to a substrate. The device can further comprise a tuning gate coupled to the substrate and formed across the epitaxial Josephson junction transmon device. According to an embodiment, a device can comprise a first superconducting region and a second superconducting region formed on a substrate. The device can further comprise an epitaxial Josephson junction tunneling channel coupled to the first superconducting region and the second superconducting region.

Semiconductor-superconductor hybrid devices with a horizontally-confined channel and methods of forming the same are described. An example semiconductor-superconductor hybrid device includes a semiconductor heterostructure formed over a substrate. The semiconductor-superconductor hybrid device may further include a superconducting layer formed over the semiconductor heterostructure. The semiconductor-superconductor hybrid device may further include a first gate, having a first top surface, formed adjacent to a first side of the semiconductor heterostructure. The semiconductor-superconductor hybrid device may further include a second gate, having a second top surface, formed adjacent to a second side, opposite to the first side, of the semiconductor heterostructure, where each of the first top surface of the first gate and the second top surface of the second gate is offset vertically from a selected surface of the semiconductor heterostructure by a predetermined offset amount.