A method of fabricating a device, comprising forming portions of electronic circuitry and a shadow wall structure over a substrate, and subsequently depositing a conducting layer over the substrate by angled deposition of a conducting material in at least a first deposition direction at an acute angle relative to the plane of the substrate. The shadow wall structure is arranged to cast a shadow in the deposition, leaving areas where the conducting material is not deposited. The shadow wall structure comprises one or more gaps each shorter than a shadow length of a respective part of the shadow wall structure casting the shadow into the gap, to prevent the conducting material forming in the gaps and to thereby create regions of said upper conducting layer that are electrically isolated from one another. These are arranged to form conducting elements for applying signals to, and/or receiving signals from, the electronic circuitry.

A method of fabricating a device, comprising forming portions of electronic circuitry and a shadow wall structure over a substrate, and subsequently depositing a conducting layer over the substrate by angled deposition of a conducting material in at least a first deposition direction at an acute angle relative to the plane of the substrate. The shadow wall structure is arranged to cast a shadow in the deposition, leaving areas where the conducting material is not deposited. The shadow wall structure comprises one or more gaps each shorter than a shadow length of a respective part of the shadow wall structure casting the shadow into the gap, to prevent the conducting material forming in the gaps and to thereby create regions of said upper conducting layer that are electrically isolated from one another. These are arranged to form conducting elements for applying signals to, and/or receiving signals from, the electronic circuitry.

A novel and useful system and method of generating quantum unitary noise using silicon based quantum dot arrays. Unitary noise is derived from a probability of detecting a particle within a quantum dot array structure comprising position based charge qubits with two time independent basis states |0> and |1>. A two level electron tunneling device such as an interface device, qubit or other quantum structure is used to generate quantum noise. The electron tunneling device includes a reservoir of particles, a quantum dot, and a barrier that is used to control tunneling between the reservoir and the quantum dot. A detector circuit connected to the device outputs a digital stream corresponding to the probability of a particle of being detected. Controlling the bias applied to the barrier controls the probability of detection. Thus, the probability density function (PDF) of the output unitary noise can be controlled to correspond to a desired probability. The unitary noise can be used in stochastic rounding by controlling the bias applied to the barrier in accordance with a remainder of numbers to be rounded.

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 quantum device with spin qubits, comprising: a semiconductor portion arranged on a buried dielectric layer of a semiconductor-on-insulator substrate also including a semiconductor support layer, wherein first distinct parts each form a confinement region of one of the qubits and are spaced apart from one another by a second part forming a coupling region between the confinement regions of the qubits; front gates each at least partially covering one of the first parts of the semiconductor portion; and wherein the support layer comprises a doped region a part of which is arranged in line with the second part of the semiconductor portion and is self-aligned with respect to the front gates, and forms a back gate controlling the coupling between the confinement regions of the qubits.

A multi-negative differential transconductance device includes a substrate conductive portion; a gate insulating layer formed by being laminated on the substrate conductive portion; a first semiconductor, a second semiconductor, and a third semiconductor which have different threshold voltages and are formed to be horizontally connected in series on the gate insulating layer; and an electrode formed at both ends of the first semiconductor and the third semiconductor. The multi-negative differential transconductance device forms a junction of three or more semiconductor materials in one device to have a plurality of peaks and valleys so that the multi-negative differential transconductance device is utilized to implement a multi-valued logic circuit which is capable of representing four or more logical states without significantly increasing an area of the negative differential transconductance device which occupies the chip. Therefore, effects of low power consumption, a reduced size, and high speed of a chip may be achieved.

Disclosed herein are quantum computing assemblies, as well as related computing devices and methods. For example, in some embodiments, a quantum computing assembly may include: a quantum device die to generate a plurality of qubits; a control circuitry die to control operation of the quantum device die; and a substrate; wherein the quantum device die and the control circuitry die are disposed on the substrate.

Disclosed herein are quantum dot devices with single electron transistor (SET) detectors. In some embodiments, a quantum dot device may include: a quantum dot formation region; a group of gates disposed on the quantum dot formation region, wherein the group of gates includes at least first, second, and third gates, spacers are disposed on sides of the first and second gates, wherein a first spacer is disposed on a side of the first gate proximate to the second gate, and a second spacer, physically separate from the first spacer, is disposed on a side of the second gate proximate to the first gate, and the third gate is disposed between the first and second gates and extends between the first and second spacers; and a SET disposed on the quantum dot formation region, proximate to the group of gates.

A method is described for controlling a spin qubit quantum device that includes a semiconducting portion, a dielectric layer covered by the semiconducting portion, a front gate partially covering an upper edge of the semiconducting portion, and a back gate. The method includes, during a manipulation of a spin state, the exposure of the device to a magnetic field B of value such that g.Math.μ.sub.B.Math.B>min(Δ(Vbg)). The method also includes the application, on the rear gate, of an electrical potential Vbg of value such that Δ(Vbg)<g.Math.μ.sub.B.Math.B+2|M.sub.SO|, and the application, on the front gate, of a confinement potential and an RF electrical signal triggering a change of spin state, with g corresponding to the Landé factor, μ.sub.B corresponding to a Bohr magneton, Δ corresponding to an intervalley energy difference in the semiconducting portion, and M.sub.SO corresponding to the intervalley spin-orbit coupling.

Quantum dot devices, and related systems and methods, are disclosed herein. In some embodiments, a quantum dot device may include a quantum well stack; a plurality of first gate lines above the quantum well stack; a plurality of second gate lines above the quantum well stack, wherein the second gate lines are perpendicular to the first gate lines; and an array of regularly spaced magnet lines.