A method includes: providing a device having a first layer and a second layer in contact with a surface of the first layer, in which the second layer includes a first superconductor material; forming a buffer material on the second layer to form an etch buffer layer, in which an etch rate selectivity of the buffer material relative to the second layer upon exposure to a photoresist developer is such that the underlying second layer is not etched during exposure of the buffer layer to the photoresist developer; depositing and removing a selected portion of a resist layer to uncover a first portion of the etch buffer layer, wherein removing the selected portion of the resist layer comprises applying the photoresist developer to the selected portion of the resist layer.

A quantum computing system that includes a quantum circuit device having at least one operating frequency; a first substrate having a first surface on which the quantum circuit device is disposed; a second substrate having a first surface that defines a recess of the second substrate, the first and second substrates being arranged such that the recess of the second substrate forms an enclosure that houses the quantum circuit device; and an electrically conducting layer that covers at least a portion of the recess of the second substrate.

A method of forming a superconductor interconnect structure is disclosed. The method includes forming a dielectric layer overlying a substrate, forming an interconnect opening in the dielectric layer, and moving the substrate to a deposition chamber. The method further includes depositing a superconducting metal in the interconnect opening, by performing a series of superconducting deposition and cooling processes to maintain a chamber temperature at or below a predetermined temperature until the superconducting metal has a desired thickness, to form a superconducting element in the superconductor interconnect structure.

Various techniques and apparatus permit fabrication of superconductive circuits. A niobium/aluminum oxide/niobium trilayer may be formed and individual Josephson Junctions (JJs) formed. A protective cap may protect a JJ during fabrication. A hybrid dielectric may be formed. A superconductive integrated circuit may be formed using a subtractive patterning and/or additive patterning. A superconducting metal layer may be deposited by electroplating and/or polished by chemical-mechanical planarization. The thickness of an inner layer dielectric may be controlled by a deposition process. A substrate may include a base of silicon and top layer including aluminum oxide. Depositing of superconducting metal layer may be stopped or paused to allow cooling before completion. Multiple layers may be aligned by patterning an alignment marker in a superconducting metal layer.

Described herein are structures that include interconnects for providing electrical connectivity in superconducting quantum circuits. One structure includes a first and a second interconnects provided over a surface of an interconnect support layer, e.g. a substrate, on which superconducting qubits are provided, a lower interconnect provided below such surface (i.e. below-plane interconnect), and vias for providing electrical interconnection between the lower interconnect and each of the first and second interconnects. Providing below-plane interconnects in superconducting quantum circuits allows realizing superconducting and mechanically stable interconnects. Implementing below-plane interconnects by bonding of two substrates, material for which could be selected, allows minimizing the amount of spurious two-level systems in the areas surrounding below-plane interconnects while allowing different choices of materials to be used. Methods for fabricating such structures are disclosed as well.

Methods and structures corresponding to superconducting apparatus including superconducting layers and traces are provided. A method for forming a superconducting apparatus includes forming a first dielectric layer on a substrate by depositing a first dielectric material on the substrate and curing the first dielectric material at a first temperature. The method further includes forming a first superconducting layer comprising a first set of patterned superconducting traces on the first dielectric layer. The method further includes forming a second dielectric layer on the first superconducting layer by depositing a second dielectric material on the first superconducting layer and curing the second dielectric material at a second temperature, where the second temperature is lower than the first temperature. The method further includes forming a second superconducting layer comprising a second set of patterned superconducting traces on the second dielectric layer.

Various techniques and apparatus permit fabrication of superconductive circuits. A niobium/aluminum oxide/niobium trilayer may be formed and individual Josephson Junctions (JJs) formed. A protective cap may protect a JJ during fabrication. A hybrid dielectric may be formed. A superconductive integrated circuit may be formed using a subtractive patterning and/or additive patterning. A superconducting metal layer may be deposited by electroplating and/or polished by chemical-mechanical planarization. The thickness of an inner layer dielectric may be controlled by a deposition process. A substrate may include a base of silicon and top layer including aluminum oxide. Depositing of superconducting metal layer may be stopped or paused to allow cooling before completion. Multiple layers may be aligned by patterning an alignment marker in a superconducting metal layer.

A low-noise wide band amplifier is realized utilizing a superconductor-insulator-superconductor (SIS) junction, quasiparticle frequency mixers connected in tandem or in cascade, a first quasiparticle mixer performs first frequency mixing with use of a first local signal having a frequency not less than twice a frequency of an input signal to the first quasiparticle mixer, a second quasiparticle mixer performs second frequency mixing with use of a second local signal having a frequency not more than twice a frequency of an input signal to the second quasiparticle mixer, and signal amplification is performed through frequency conversion by extracting, from among a plurality of signals generated with the first and the second frequency mixing, a signal in a frequency band not more than a frequency band of the signal before the first frequency mixing and the second frequency mixing, using a transmission line or a filter.

Methods and structures corresponding to superconducting apparatus including superconducting layers and traces are provided. A method for forming a superconducting apparatus includes forming a first dielectric layer on a substrate by depositing a first dielectric material on the substrate and curing the first dielectric material at a first temperature. The method further includes forming a first superconducting layer comprising a first set of patterned superconducting traces on the first dielectric layer. The method further includes forming a second dielectric layer on the first superconducting layer by depositing a second dielectric material on the first superconducting layer and curing the second dielectric material at a second temperature, where the second temperature is lower than the first temperature. The method further includes forming a second superconducting layer comprising a second set of patterned superconducting traces on the second dielectric layer.

Various techniques and apparatus permit fabrication of superconductive circuits. A superconducting integrated circuit comprising a superconducting stud via, a kinetic inductor, and a capacitor may be formed. Forming a superconducting stud via in a superconducting integrated circuit may include masking with a hard mask and masking with a soft mask. Forming a superconducting stud via in a superconducting integrated circuit may include depositing a dielectric etch stop layer. Interlayer misalignment in the fabrication of a superconducting integrated circuit may be measured by an electrical vernier. Interlayer misalignment in the fabrication of a superconducting integrated circuit may be measured by a chain of electrical verniers and a Wheatstone bridge. A superconducting integrated circuit with three or more metal layers may include an enclosed, matched, on-chip transmission line. A metal wiring layer in a superconducting integrated circuit may be encapsulated.