A mixed semiconductor-superconductor platform is fabricated in phases. In a masking phase, a dielectric mask is formed on a substrate, such that the dielectric mask leaves one or more regions of the substrate exposed. In a selective area growth phase, a semiconductor material is selectively grown on the substrate in the one or more exposed regions. In a superconductor growth phase, a layer of superconducting material is formed, at least part of which is in direct contact with the selectively grown semiconductor material. The mixed semiconductor-superconductor platform comprises the selectively grown semiconductor material and the superconducting material in direct contact with the selectively grown semiconductor material.

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.

Qubit circuits having components formed deep in a substrate are described. The qubit circuits can be manufactured using existing integrated-circuit technologies. By forming components such as superconducting current loops, inductive, and/or capacitive components deep in the substrate, the footprint of the qubit circuit integrated within the substrate can be reduced. Additionally, coupling efficiency to and from the qubit can be improved and losses in the qubit circuit may be reduced.

Qubit circuits having components formed deep in a substrate are described. The qubit circuits can be manufactured using existing integrated-circuit technologies. By forming components such as superconducting current loops, inductive, and/or capacitive components deep in the substrate, the footprint of the qubit circuit integrated within the substrate can be reduced. Additionally, coupling efficiency to and from the qubit can be improved and losses in the qubit circuit may be reduced.

An electronic device (e.g., a diode) is provided that includes a substrate and a patterned layer of superconducting material disposed over the substrate. The patterned layer forms a first electrode, a second electrode, and a loop coupling the first electrode with the second electrode by a first channel and a second channel. The first channel and the second channel have different minimum widths. For a range of current magnitudes, when a magnetic field is applied to the patterned layer of superconducting material, the conductance from the first electrode to the second electrode is greater than the conductance from the second electrode to the first electrode.

An electronic device (e.g., a diode) is provided that includes a substrate and a patterned layer of superconducting material disposed over the substrate. The patterned layer forms a first electrode, a second electrode, and a loop coupling the first electrode with the second electrode by a first channel and a second channel. The first channel and the second channel have different minimum widths. For a range of current magnitudes, when a magnetic field is applied to the patterned layer of superconducting material, the conductance from the first electrode to the second electrode is greater than the conductance from the second electrode to the first electrode.

An electronic device (e.g., a diode) is provided that includes a substrate and a patterned layer of superconducting material disposed over the substrate. The patterned layer forms a first electrode, a second electrode, and a loop coupling the first electrode with the second electrode by a first channel and a second channel. The first channel and the second channel have different minimum widths. For a range of current magnitudes, when a magnetic field is applied to the patterned layer of superconducting material, the conductance from the first electrode to the second electrode is greater than the conductance from the second electrode to the first electrode.

A method for fabricating a bridge structure in a quantum mechanical device includes providing a substructure including a substrate having deposited thereon a layer of a first superconducting material divided into a first portion, a second portion and a third portion that are electrically insulated from each other; depositing a sacrificial layer on the substructure; electrically connecting the first portion and the second portion with a strip of a second superconducting material, the second superconducting material being different from the first superconducting material; and removing a portion of the sacrificial layer so as to form a bridge structure over the third portion between the first portion and the second portion, the bridge structure electrically connecting the first portion to the second portion while not electrically connecting the third portion to the first portion and not electrically connecting the third portion to the second portion.

Test structures and methods for superconducting bump bond electrical characterization are used to verify the superconductivity of bump bonds that electrically connect two superconducting integrated circuit chips fabricated using a flip-chip process, and can also ascertain the self-inductance of bump bond(s) between chips. The structures and methods leverage a behavioral property of superconducting DC SQUIDs to modulate a critical current upon injection of magnetic flux in the SQUID loop, which behavior is not present when the SQUID is not superconducting, by including bump bond(s) within the loop, which loop is split among chips. The sensitivity of the bump bond superconductivity verification is therefore effectively perfect, independent of any multi-milliohm noise floor that may exist in measurement equipment.

Josephson junction (JJ) structures are disclosed. In some embodiments, a JJ structure may include a first superconducting structure and a second superconducting structure disposed on a plane parallel to a silicon wafer surface. A non-superconducting structure may be disposed between the first superconducting structure and the second superconducting structure. A direction of current flow through the non-superconducting structure may be parallel to the silicon wafer surface.