One superconducting qubit device package disclosed herein includes a die having a first face and an opposing second face, and a package substrate having a first face and an opposing second face. The die includes a quantum device including a plurality of superconducting qubits and a plurality of resonators on the first face of the die, and a plurality of conductive pathways coupled between conductive contacts at the first face of the die and associated ones of the plurality of superconducting qubits or of the plurality of resonators. The second face of the package substrate also includes conductive contacts. The device package further includes first level interconnects disposed between the first face of the die and the second face of the package substrate, coupling the conductive contacts at the first face of the die with associated conductive contacts at the second face of the package substrate.

Superconducting tunnel junctions for use in, for instance, quantum processors. In one example, a quantum processor can have at least one qubit structure. The at least one qubit structure includes a first aluminum layer, a second aluminum layer, and a crystalline dielectric layer disposed between the first aluminum layer and the second aluminum layer. The crystalline dielectric layer includes a spinel crystal structure.

Methods, systems and apparatus for forming Josephson junctions with reduced stray inductance. In one aspect, a device includes a substrate; a first superconductor layer on the substrate; an insulator layer on the first superconductor layer; a second superconductor layer on the insulator layer, wherein the first superconductor layer, the insulator layer, and the second superconductor layer form a superconductor tunnel junction; and a third superconductor layer directly on a surface of the first superconductor layer and directly on a surface of the second superconductor layer to provide a first contact to the superconducting tunnel junction and a second contact to the superconductor tunnel junction, respectively.

A Josephson voltage standard includes: electrical conductors that receive bias currents and radiofrequency biases; a first Josephson junction array that: includes a first Josephson junction and produces a first voltage reference from the first bias current and the third bias current; a second Josephson junction array in electrical communication with the first Josephson junction array and that: includes a second Josephson junction; receives the second bias current; receives the third bias current; receives the second radiofrequency bias; and produces a second voltage reference from the second bias current and the third bias current; a first voltage reference output tap in electrical communication with the first Josephson junction array and that receives the first voltage reference from the first Josephson junction array such that the first voltage reference is electrically available at the first voltage reference output tap; and a second voltage reference output tap.

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.

Techniques related to vertical silicon-on-metal superconducting quantum interference devices and method of fabricating the same are provided. Also provided are associated flux control and biasing circuitry. A superconductor structure can comprise a silicon-on-metal substrate that can comprise a first superconducting layer, comprising a first superconducting material, between a first crystalline silicon layer and a second crystalline silicon layer. The superconducting structure can also comprise a first via comprising a first Josephson junction and a second via comprising a second Josephson junction. The first via and the second via can be formed between the first superconducting layer and a second superconducting layer, comprising a second superconducting material. An electrical loop around a defined area of the second crystalline silicon layer can comprise the first via comprising the first Josephson junction, the second via comprising the second Josephson junction, the first superconducting layer, and the second superconducting layer.

A method for forming at least part of a quantum information processing device is presented. The method includes providing a first electrically-conductive layer formed of a first electrically-conductive material (100′) on a principal surface of a substrate (10), depositing a layer of dielectric material on the first electrically-conductive material, patterning the layer of dielectric material to form a pad of dielectric material and to reveal a first region of the first electrically-conductive layer, depositing a second electrically-conductive layer (104′) on the pad of dielectric material and on the first region of the first electrically-conductive layer, patterning the second electrically-conductive layer and removing the pad of dielectric material using isotropic gas phase etching.

A device includes a first substrate having a principal surface; a second substrate having a principal surface, in which the first substrate is bump-bonded to the second substrate such that the principal surface of the first substrate faces the principal surface of the second substrate; a circuit element having a microwave frequency resonance mode, in which a first portion of the circuit element is arranged on the principal surface of the first substrate and a second portion of the circuit element is arranged on the principal surface of the second substrate; and a first bump bond connected to the first portion of the circuit element and to the second portion of the circuit element, in which the first superconductor bump bond provides an electrical connection between the first portion and the second portion.

Methods, devices, and systems are described for forming a superconducting qubit. An example device may comprise a substrate having a first surface and a patterned layer adjacent the substrate and comprising tantalum in an alpha phase. The patterned layer may comprise at least a part of a structure for storing a quantum state.

There is described herein a method for fabricating a tunnel junction. The method comprises coating a substrate with an inorganic resist layer and forming support pillars in the resist layer; fabricating a mask on the resist layer from a first inorganic material, the mask having at least one opening; removing the resist layer from beneath the mask, leaving behind the support pillars supporting the mask above the substrate; performing shadow evaporation on the substrate through the at least one opening of the mask to form the tunnel junction on the substrate; and removing the mask and the support pillars from the substrate.