Techniques regarding quantum transducers are provided. For example, one or more embodiments described herein can include an apparatus that can comprise a superconducting microwave resonator having a microstrip architecture that can include a dielectric substrate positioned between a superconducting waveguide and a superconducting ground plane. The superconducting waveguide can have a first material composition. Also, the superconducting ground plane can have a second material composition that is distinct from the first material composition. Further, an optical resonator can be arranged with the dielectric substrate.

Techniques regarding quantum transducers are provided. For example, one or more embodiments described herein can include an apparatus that can comprise a superconducting microwave resonator having a microstrip architecture that can include a dielectric substrate positioned between a superconducting waveguide and a superconducting ground plane. The superconducting waveguide can have a first material composition. Also, the superconducting ground plane can have a second material composition that is distinct from the first material composition. Further, an optical resonator can be arranged with the dielectric substrate.

Methods and systems for estimating localization lengths in hybrid superconductor-semiconductor quantum devices are described. A method for estimating localization lengths in a hybrid superconductor-semiconductor quantum device includes constructing a statistical model for extracting localization lengths based on an implicit description of nonlocal conductance measurements associated with a physical representation of the hybrid superconductor-semiconductor quantum device. The method further includes, using a processor, estimating the localization lengths in the hybrid superconductor-semiconductor quantum device by a joint prior distribution enforcing smoothness over a function of gate voltages and extracted localization lengths for the hybrid superconductor-semiconductor quantum device.

Methods and systems for estimating localization lengths in hybrid superconductor-semiconductor quantum devices are described. A method for estimating localization lengths in a hybrid superconductor-semiconductor quantum device includes constructing a statistical model for extracting localization lengths based on an implicit description of nonlocal conductance measurements associated with a physical representation of the hybrid superconductor-semiconductor quantum device. The method further includes, using a processor, estimating the localization lengths in the hybrid superconductor-semiconductor quantum device by a joint prior distribution enforcing smoothness over a function of gate voltages and extracted localization lengths for the hybrid superconductor-semiconductor quantum device.

A structure includes a first substrate, a lower wire formed of a superconducting material and provided on the first substrate, a control post formed of a superconducting material including a metal and provided on the lower wire, an upper wire formed of a superconducting material and provided on the control post, and a second substrate provided on the upper wire. The control post includes a first electrode, a junction surface, and a second electrode, which is joined to the first electrode via the junction surface. The first and second electrodes are formed of the same type of metal.

A structure includes a first substrate, a lower wire formed of a superconducting material and provided on the first substrate, a control post formed of a superconducting material including a metal and provided on the lower wire, an upper wire formed of a superconducting material and provided on the control post, and a second substrate provided on the upper wire. The control post includes a first electrode, a junction surface, and a second electrode, which is joined to the first electrode via the junction surface. The first and second electrodes are formed of the same type of metal.

Aa superconducting computing apparatus includes: frequency tunable devices connected to each other and arranged in a shape; a ferromagnetic film disposed adjacent to the frequency tunable devices and having an up magnetic domain or a down magnetic domain; and a control circuit configured to adjust a position of a magnetic domain wall in the ferromagnetic film by applying a current to the ferromagnetic film, wherein the position of the magnetic domain wall controls a resonant frequency of the frequency tunable devices.

Aa superconducting computing apparatus includes: frequency tunable devices connected to each other and arranged in a shape; a ferromagnetic film disposed adjacent to the frequency tunable devices and having an up magnetic domain or a down magnetic domain; and a control circuit configured to adjust a position of a magnetic domain wall in the ferromagnetic film by applying a current to the ferromagnetic film, wherein the position of the magnetic domain wall controls a resonant frequency of the frequency tunable devices.

A superconducting quantum circuit includes first to fourth qubits, and a coupler including first and second electrodes and a nonlinear element bridging the first and second electrodes, wherein each of the first to fourth qubits includes a resonator including a SQUID loop circuit and a capacitor connected in parallel to the loop circuit, the first and second qubits and the third and fourth qubits capacitively coupled to the first and second electrodes of the coupler, respectively, wherein a magnitude relationship among a capacitance value C of a capacitive coupling between each of the first to fourth qubits and the coupler, a capacitance value C.sub.J of the capacitor connected in parallel to the loop circuit for each of the first to fourth qubits, and a capacitance value C.sub.g between the first and second electrodes of the coupler, is set to C.sub.J>C.sub.g>C.

A superconducting quantum circuit includes first to fourth qubits, and a coupler including first and second electrodes and a nonlinear element bridging the first and second electrodes, wherein each of the first to fourth qubits includes a resonator including a SQUID loop circuit and a capacitor connected in parallel to the loop circuit, the first and second qubits and the third and fourth qubits capacitively coupled to the first and second electrodes of the coupler, respectively, wherein a magnitude relationship among a capacitance value C of a capacitive coupling between each of the first to fourth qubits and the coupler, a capacitance value C.sub.J of the capacitor connected in parallel to the loop circuit for each of the first to fourth qubits, and a capacitance value C.sub.g between the first and second electrodes of the coupler, is set to C.sub.J>C.sub.g>C.