Abstract: 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.

Abstract: Superconducting integrated circuits may advantageously employ superconducting resonators coupled to a microwave transmission line to efficiently address superconducting flux storage devices. In an XY-addressing scheme, a global flux bias may be applied to a number of superconducting flux storage devices via a low-frequency address line, and individual superconducting flux storage devices addressed via application of high-frequency pulses via resonators driven by the microwave transmission line. Frequency multiplexing can be employed to provide signals to two or more resonators. A low-frequency current bias may be combined with a high-frequency current in one or more superconducting resonators to provide Z-addressing. A low-frequency current bias may be combined with a high-frequency current in one or more superconducting resonators to eliminate a flux bias line.

Abstract: A device is dynamically isolated via a broadband switch that includes a plurality of cascade elements in series, wherein each cascade element comprises a first set of SQUIDs in series, a matching capacitor, and a second set of SQUIDs in series. The broadband switch is set to a passing state via flux bias lines during programming and readout of the device and set to a suppression state during device's calculation to reduce operation errors at the device. A device is electrically isolated from high-frequencies via an unbiased broadband switch. A device is coupled to a tunable thermal bath that includes a broadband switch.

Abstract: A superconducting readout system employing a microwave transmission line, and a microwave superconducting resonator communicatively coupled to the microwave transmission line, and including a superconducting quantum interference device (SQUID), may be advantageously calibrated at least in part by measuring a resonant frequency of the microwave superconducting resonator in response to a flux bias applied to the SQUID, measuring a sensitivity of the resonant frequency in response to the flux bias, and selecting an operating frequency and a sensitivity of the microwave superconducting resonator based at least in part on a variation of the resonant frequency as a function of the flux bias. The flux bias may be applied to the SQUID by an interface inductively coupled to the SQUID. Calibration of the superconducting readout system may also include determining at least one of a propagation delay, a microwave transmission line delay, and a microwave transmission line phase offset.

Abstract: Systems and methods for measuring noise in discrete regions of multi-layer superconducting fabrication stacks are described. Methods for measuring noise in spatial regions of a superconducting fabrication stacks may include the use of resonators, each having a different geometry. As many resonators as spatial regions are fabricated. Data collected from the resonators may be used to calculate fill fractions and spin densities for different spatial regions of the superconducting fabrication stack. The data may be collected via on-chip electron-spin resonance. The superconducting fabrications may be part of a fabrication stack for a superconducting processor, for example a quantum processor, and the spatial region studied may be proximate to qubit wiring layers.

Abstract: A device is dynamically isolated via a broadband switch that includes a plurality of cascade elements in series, wherein each cascade element comprises a first set of SQUIDs in series, a matching capacitor, and a second set of SQUIDs in series. The broadband switch is set to a passing state via flux bias lines during programming and readout of the device and set to a suppression state during device's calculation to reduce operation errors at the device. A device is electrically isolated from high-frequencies via an unbiased broadband switch. A device is coupled to a tunable thermal bath that includes a broadband switch.

Abstract: Methods for mitigating microwave crosstalk and forming a component in a superconducting integrated circuit are discussed. Mitigating microwave crosstalk involves forming a microwave shield within the superconducting integrated circuit, the superconducting integrated circuit including a microwave sensitive component. The microwave shield is formed from a base layer and one or more sides, and the footprint of the microwave sensitive component is contained within the footprint of the microwave shielding base layer, with the one or more sides extending around at least a portion of the microwave sensitive component. Forming a component involves depositing a first metal layer, depositing a dielectric layer overlying the first metal layer, the dielectric layer comprising Nb2O5 that is deposited by atomic layer deposition, and depositing a second metal layer overlying the dielectric layer.

Abstract: A device is dynamically isolated via a broadband switch that includes a plurality of cascade elements in series, wherein each cascade element comprises a first set of SQUIDs in series, a matching capacitor, and a second set of SQUIDs in series. The broadband switch is set to a passing state via flux bias lines during programming and readout of the device and set to a suppression state during device's calculation to reduce operation errors at the device. A device is electrically isolated from high-frequencies via an unbiased broadband switch. A device is coupled to a tunable thermal bath that includes a broadband switch.

Abstract: A superconducting circuit may include a transmission line having at least one transmission line inductance, a superconducting resonator, and a coupling capacitance that communicatively couples the superconducting resonator to the transmission line. The transmission line inductance may have a value selected to at least partially compensate for a variation in a characteristic impedance of the transmission line, the variation caused at least in part by the coupling capacitance. The coupling capacitance may be distributed along the length of the transmission line. A superconducting circuit may include a transmission line having at least one transmission line capacitance, a superconducting resonator, and a coupling inductance that communicatively couples the superconducting resonator to the transmission line. The transmission line capacitance may be selected to at least partially compensate for a variation in coupling strength between the superconducting resonator and the transmission line.

Abstract: A superconducting circuit may include a transmission line having at least one transmission line inductance, a superconducting resonator, and a coupling capacitance that communicatively couples the superconducting resonator to the transmission line. The transmission line inductance may have a value selected to at least partially compensate for a variation in a characteristic impedance of the transmission line, the variation caused at least in part by the coupling capacitance. The coupling capacitance may be distributed along the length of the transmission line. A superconducting circuit may include a transmission line having at least one transmission line capacitance, a superconducting resonator, and a coupling inductance that communicatively couples the superconducting resonator to the transmission line. The transmission line capacitance may be selected to at least partially compensate for a variation in coupling strength between the superconducting resonator and the transmission line.

Abstract: A device is dynamically isolated via a broadband switch that includes a plurality of cascade elements in series, wherein each cascade element comprises a first set of SQUIDs in series, a matching capacitor, and a second set of SQUIDs in series. The broadband switch is set to a passing state via flux bias lines during programming and readout of the device and set to a suppression state during device's calculation to reduce operation errors at the device. A device is electrically isolated from high-frequencies via an unbiased broadband switch. A device is coupled to a tunable thermal bath that includes a broadband switch.

Abstract: 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.

Abstract: A superconducting readout system employing a microwave transmission line, and a microwave superconducting resonator communicatively coupled to the microwave transmission line, and including a superconducting quantum interference device (SQUID), may be advantageously calibrated at least in part by measuring a resonant frequency of the microwave superconducting resonator in response to a flux bias applied to the SQUID, measuring a sensitivity of the resonant frequency in response to the flux bias, and selecting an operating frequency and a sensitivity of the microwave superconducting resonator based at least in part on a variation of the resonant frequency as a function of the flux bias. The flux bias may be applied to the SQUID by an interface inductively coupled to the SQUID. Calibration of the superconducting readout system may also include determining at least one of a propagation delay, a microwave transmission line delay, and a microwave transmission line phase offset.

Abstract: A superconducting input and/or output system employs at least one microwave superconducting resonator. The microwave superconducting resonator(s) may be communicatively coupled to a microwave transmission line. Each microwave superconducting resonator may include a first and a second DC SQUID, in series with one another and with an inductance (e.g., inductor), and a capacitance in parallel with the first and second DC SQUIDs and inductance. Respective inductive interfaces are operable to apply flux bias to control the DC SQUIDs. The second DC SQUID may be coupled to a Quantum Flux Parametron (QFP), for example as a final element in a shift register. A superconducting parallel plate capacitor structure and method of fabricating such are also taught.

Abstract: Superconducting integrated circuits may advantageously employ superconducting resonators coupled to a microwave transmission line to efficiently address superconducting flux storage devices. In an XY-addressing scheme, a global flux bias may be applied to a number of superconducting flux storage devices via a low-frequency address line, and individual superconducting flux storage devices addressed via application of high-frequency pulses via resonators driven by the microwave transmission line. Frequency multiplexing can be employed to provide signals to two or more resonators. A low-frequency current bias may be combined with a high-frequency current in one or more superconducting resonators to provide Z-addressing. A low-frequency current bias may be combined with a high-frequency current in one or more superconducting resonators to eliminate a flux bias line.

Abstract: 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.

Abstract: A superconducting input and/or output system employs at least one microwave superconducting resonator. The microwave superconducting resonator(s) may be communicatively coupled to a microwave transmission line. Each microwave superconducting resonator may include a first and a second DC SQUID, in series with one another and with an inductance (e.g., inductor), and a capacitance in parallel with the first and second DC SQUIDs and inductance. Respective inductive interfaces are operable to apply flux bias to control the DC SQUIDs. The second DC SQUID may be coupled to a Quantum Flux Parametron (QFP), for example as a final element in a shift register. A superconducting parallel plate capacitor structure and method of fabricating such are also taught.

Abstract: A superconducting circuit may include a transmission line having at least one transmission line inductance, a superconducting resonator, and a coupling capacitance that communicatively couples the superconducting resonator to the transmission line. The transmission line inductance may have a value selected to at least partially compensate for a variation in a characteristic impedance of the transmission line, the variation caused at least in part by the coupling capacitance. The coupling capacitance may be distributed along the length of the transmission line. A superconducting circuit may include a transmission line having at least one transmission line capacitance, a superconducting resonator, and a coupling inductance that communicatively couples the superconducting resonator to the transmission line. The transmission line capacitance may be selected to at least partially compensate for a variation in coupling strength between the superconducting resonator and the transmission line.

Abstract: Apparatus and methods advantageously provide parallel-plate capacitors in superconducting integrated circuits. A method may include forming a metal-oxide layer to overlie at least a portion of a first capacitor plate, the first capacitor plate comprising a superconductive material, and depositing a second capacitor plate to overlie at least a portion of the metal-oxide layer, the second capacitor plate comprising a superconductive material. The method may include depositing a base electrode of superconductive material to overlie at least a portion of a substrate, depositing the first capacitor plate to overlie at least a portion of the base electrode, and superconductingly electrically coupled to the base electrode, and depositing a counter electrode of superconductive material to overlie at least a portion of the second capacitor plate, the counter electrode superconductingly electrically coupled to the second capacitor plate.

Abstract: 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.