This disclosure describes devices which comprise a superconducting circuit and a circuit connector which couples the superconducting circuit to external circuitry. The superconducting circuit comprises a circuit resonator and a transmission line coupled between the circuit connector and the circuit resonator. The length of transmission line is such that the current which passes between the circuit connector and the transmission line is substantially zero when a drive signal is applied to the circuit resonator through the transmission line.

Transducers and methods of making the same include a substrate having a cavity with a diameter that supports whispering gallery modes at a frequency of an input signal. A focusing structure in the cavity focuses the electric field of the input signal. A resonator directly under the focusing structure has a crystalline structure that generates an electro-optic effect when exposed to electrical fields. An electric field of the input signal modulates an output signal in the resonator via the electro-optic effect.

Transducers and methods of making the same include a substrate having a cavity with a diameter that supports whispering gallery modes at a frequency of an input signal. A focusing structure in the cavity focuses the electric field of the input signal. A resonator directly under the focusing structure has a crystalline structure that generates an electro-optic effect when exposed to electrical fields. An electric field of the input signal modulates an output signal in the resonator via the electro-optic effect.

Transducers and methods of making the same include a substrate having a cavity with a diameter that supports whispering gallery modes at a frequency of an input signal. A focusing structure in the cavity focuses the electric field of the input signal. A resonator directly under the focusing structure has a crystalline structure that generates an electro-optic effect when exposed to electrical fields. An electric field of the input signal modulates an output signal in the resonator via the electro-optic effect.

A waveguide structure includes a signal line and two static lines. The signal line is disposed between the static lines in a first direction. The static lines and the signal line are disposed parallel to one another. Each static line includes a first conductive pattern, a second conductive pattern, and a third conductive pattern. The first conductive pattern and the signal line are disposed on an identical plane of a dielectric layer. A thickness of the first conductive pattern is substantially equal to a thickness of the signal line. The second conductive pattern is disposed on the first conductive pattern. A width of the first conductive pattern is larger than a width of the second conductive pattern in the first direction. The third conductive pattern is disposed on the second conductive pattern. A width of the third conductive pattern is larger than the width of the second conductive pattern.

In some aspects, a quantum information processing circuit includes a lumped-element device on the surface of a dielectric substrate. The lumped-element device can include a capacitor pad and an inductive transmission line. The capacitor pad can be capacitively coupled to another capacitor pad. The inductive transmission line can reside in an interior clearance area defined by an inner boundary of the capacitor pad. The lumped-element device can be, for example, a resonator device or a filter device. The inductive transmission line can be, for example, a meander inductor.

A technique relates to a superconducting airbridge on a structure. A first ground plane, resonator, and second ground plane are formed on a substrate. A first lift-off pattern is formed of a first lift-off resist and a first photoresist. The first photoresist is deposited on the first lift-off resist. A superconducting sacrificial layer is deposited while using the first lift-off pattern. The first lift-off pattern is removed. A cross-over lift-off pattern is formed of a second lift-off resist and a second photoresist. The second photoresist is deposited on the second lift-off resist. A cross-over superconducting material is deposited to be formed as the superconducting airbridge while using the cross-over lift-off pattern. The cross-over lift-off pattern is removed. The superconducting airbridge is formed to connect the first and second ground planes by removing the superconducting sacrificial layer underneath the cross-over superconducting material. The superconducting airbridge crosses over the resonator.

A technique relates to a superconducting airbridge on a structure. A first ground plane, resonator, and second ground plane are formed on a substrate. A first lift-off pattern is formed of a first lift-off resist and a first photoresist. The first photoresist is deposited on the first lift-off resist. A superconducting sacrificial layer is deposited while using the first lift-off pattern. The first lift-off pattern is removed. A cross-over lift-off pattern is formed of a second lift-off resist and a second photoresist. The second photoresist is deposited on the second lift-off resist. A cross-over superconducting material is deposited to be formed as the superconducting airbridge while using the cross-over lift-off pattern. The cross-over lift-off pattern is removed. The superconducting airbridge is formed to connect the first and second ground planes by removing the superconducting sacrificial layer underneath the cross-over superconducting material. The superconducting airbridge crosses over the resonator.

A signal transmission line includes a signal conductor and an array of resonators. The resonators can include split resonators. The array of resonators can partially overlap with the signal conductor of the signal transmission line. In some embodiments, the portion of the signal conductor overlapping with the split ring resonators is wider than the portion of the signal conductor outside the overlapping area. The signal transmission line can be tuned for a range of frequencies. For example, the signal transmission line can be tuned to have an absolute value of a s-parameter less than or equal to 1 dB for a range of frequencies. The signal transmission line can be less than or equal to 200 microns in thickness and may also be flexible.

A resonator includes a junction element including a Josephson junction and a fishbone-type waveguide coupled by the junction element.