Abstract: 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 base; a fin extending away from the base, wherein the fin includes a quantum well layer; a gate above the fin; and a material on side faces of the fin; wherein the fin has a width between its side faces, and the fin is strained in the direction of the width.

Abstract: 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 quantum well stack including a quantum well layer and a barrier layer; a first gate metal above the quantum well stack, wherein the barrier layer is between the first gate metal and the quantum well layer; and a second gate metal above the quantum well stack, wherein the barrier layer is between the second gate metal and the quantum well layer, and a material structure of the second gate metal is different from a material structure of the first gate metal.

Abstract: 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 quantum well stack; a first gate and an adjacent second gate above the quantum well stack; and a gate wall between the first gate and the second gate, wherein the gate wall includes a first dielectric material and a second dielectric material different from the first dielectric material.

Abstract: 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 quantum well stack; a first gate above the quantum well stack, wherein the first gate includes a first gate metal and a first gate dielectric layer; and a second gate above the quantum well stack, wherein the second gate includes a second gate metal and a second gate dielectric layer, and the second gate dielectric layer extends over the first gate.

Abstract: Embodiments of the present disclosure relate to quantum circuit assemblies implementing superconducting qubits, e.g., transmons, in which SQUID loops and portions of FBLs configured to magnetically couple to the SQUID loops extend substantially vertically. In contrast to conventional implementations, for a vertical SQUID according to various embodiments of the present disclosure, a line that is perpendicular to the SQUID loop is parallel to the qubit substrate. A corresponding FBL is also provided in a vertical arrangement, in order to achieve efficient magnetic coupling to the vertical SQUID loop, by ensuring that at least a portion of the FBL designed to conduct current responsible for generating magnetic field for tuning qubit frequency is substantially perpendicular to the substrate.

Abstract: Various embodiments of the present disclosure present quantum circuit assemblies implementing vertically-stacked parallel-plate capacitors. Such capacitors include first and second capacitor plates which are parallel to one another and separated from one another by a gap measured along a direction perpendicular to the qubit plane, i.e. measured vertically. Fabrication techniques for manufacturing such capacitors are also disclosed. Vertically-stacked parallel-plate capacitors may help increasing coherence times of qubits, facilitate use of three-dimensional and stacked designs for quantum circuit assemblies, and may be particularly advantageous for realizing device scalability and use of 300-millimeter fabrication processes.

Abstract: Embodiments of the present disclosure describe a method of fabricating spin qubit device assemblies that utilize dopant-based spin qubits, i.e. spin qubit devices which operate by including a donor or an acceptor dopant atom in a semiconductor host layer. The method includes, first, providing a pair of gate electrodes over a semiconductor host layer, and then providing a window structure between the first and second gate electrodes, the window structure being a continuous solid material extending between the first and second electrodes and covering the semiconductor host layer except for an opening through which a dopant atom is to be implanted in the semiconductor host layer. By using a defined gate-first process, the method may address the scalability challenges and create a deterministic path for fabricating dopant-based spin qubits in desired locations, promoting wafer-scale integration of dopant-based spin qubit devices for use in quantum computing devices.

Abstract: Embodiments of the present disclosure describe use of isotopically purified materials in donor- or acceptor-based spin qubit devices and assemblies. An exemplary spin qubit device assembly may include a semiconductor host layer that includes an isotopically purified material, a dopant atom in the semiconductor host layer, and a gate proximate to the dopant atom. An isotopically purified material may include a lower atomic-percent of isotopes with nonzero nuclear spin than the natural abundance of those isotopies in the non-isotopically purified material. Reducing the presence of isotopes with nonzero nuclear spin in a semiconductor host layer may improve qubit coherence and thus performance of spin qubit devices and assemblies.

Abstract: Embodiments of the present disclosure describe two approaches to providing flux bias line structures for superconducting qubit devices. The first approach, applicable to flux bias line structures that include at least one portion that terminates with a ground connection, resides in terminating such a portion with a ground connection that is electrically isolated from the common ground plane of a quantum circuit assembly. The second approach resides in providing a SQUID loop of a superconducting qubit device and a portion of the flux bias line structure over a portion of a substrate that is elevated with respect to other portions of the substrate. These approaches may be used or alone or in combination, and may improve grounding of and reduce crosstalk caused by flux bias lines in quantum circuit assemblies.

Abstract: 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 base; a fin extending away from the base, wherein the fin has a first side face and a second side face, and the fin includes a quantum well layer; and a gate above the fin, wherein the gate extends down along the first side face.

Abstract: Disclosed herein are fabrication techniques for providing metal gates in quantum devices, as well as related quantum devices. For example, in some embodiments, a method of manufacturing a quantum device may include providing a gate dielectric over a qubit device layer, providing over the gate dielectric a pattern of non-metallic elements referred to as “gate support elements,” and depositing a gate metal on sidewalls of the gate support elements to form a plurality of gates of the quantum device.

Abstract: 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 quantum well stack; a first gate and an adjacent second gate above the quantum well stack; and a multi-spacer between the first gate and the second gate, wherein the multi-spacer includes a first spacer and a second spacer different from the first spacer, and the first spacer is at least partially between the quantum well stack and the second spacer.

Abstract: Embodiments of the present disclosure describe quantum circuit assemblies utilizing triaxial cables to communicate signals to/from quantum circuit components. One assembly includes a cooling apparatus for cooling a quantum circuit component that includes at least one qubit device. The cooling apparatus includes at least one triaxial connector for providing signals to and/or receiving signals from the quantum circuit component using one or more triaxial cables. Other assemblies include quantum circuit components and various electronic components (e.g. attenuators, filters, or amplifiers) for use within the cooling apparatus, adapted to be used with triaxial cables by incorporating triaxial connectors as well.

Abstract: 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 quantum well stack; a first gate above the quantum well stack, wherein the first gate includes a first gate metal and a first gate dielectric; and a second gate above the quantum well stack, wherein the second gate includes a second gate metal and a second gate dielectric, and the first gate is at least partially between a portion of the second gate and the quantum well stack.

Abstract: 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 base; a fin extending away from the base, wherein the fin includes a quantum well layer; a first dielectric material around a bottom portion of the fin; and a second dielectric material around a top portion of the fin, wherein the second dielectric material is different from the first dielectric material.

Abstract: A quantum dot device is disclosed that includes a quantum well stack, a first and a second plunger gates above the quantum well stack, and a passive barrier element provided in a portion of the quantum well stack between the first and the second plunger gates. The passive barrier element may serve as means for localizing charge in the quantum dot device and may be used to replace charge localization control by means of a barrier gate. In general, a quantum dot device with a plurality of plunger gates provided over a given quantum well stack may include a respective passive barrier element between any, or all, of adjacent plunger gates in the manner as described for the first and second plunger gates.

Abstract: 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 quantum well stack; a first gate and an adjacent second gate above the quantum well stack; and a gate wall between the first gate and the second gate, wherein the gate wall includes a spacer and a capping material, the spacer has a top and a bottom, the bottom of the spacer is between the top of the spacer and the quantum well stack, and the capping material is proximate to the top of the spacer.

Abstract: 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 quantum well stack; a layer of gate dielectric above the quantum well stack; a first gate metal and a second gate metal above the layer of gate dielectric; and a gate wall between the first gate metal and the second gate metal, wherein the gate wall is above the layer of gate dielectric, and the gate wall includes a first dielectric material and a second dielectric material different from the first dielectric material.

Abstract: Embodiments of the present disclosure propose two methods for integrating vacancy centers (VCs) on semiconductor substrates for forming VC-based spin qubit devices. The first method is based on using a self-assembly process for integrating VC islands on a semiconductor substrate. The second method is based on using a buffer layer of a III-N semiconductor material over a semiconductor substrate, and then integrating VC islands in an insulating carbon-based material such as diamond that is either grown as a layer on the III-N buffer layer or grown in the openings formed in the III-N buffer layer. Integration of VC islands on semiconductor substrates typically used in semiconductor manufacturing according to any of these methods may provide a substantial improvement with respect to conventional approaches to building VC-based spin qubit devices and may promote wafer-scale integration of VC-based spin qubits for use in quantum computing devices.

Abstract: Embodiments of the present disclosure propose quantum circuit assemblies with transmission lines and/or capacitors that include layer-conductors oriented perpendicular to a substrate (i.e. oriented vertically) or a qubit die, with at least portions of the vertical layer-conductors being at least partially buried in the substrate. Such layer-conductors may form ground and signal planes of transmission lines or capacitor plates of capacitors of various quantum circuit assemblies.