An aspect includes one or more board layers. A first chip cavity is formed within the one or more board layers, wherein a first Josephson amplifier or Josephson mixer is disposed within the first chip cavity. The first Josephson amplifier or Josephson mixer comprises at least one port, each port connected to at least one connector disposed on at least one of the one or more board layers, wherein at least one of the one or more board layers comprises a circuit trace formed on the at least one of the one or more board layers.

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.

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.

Technology is disclosed herein that the enhances the measurability and scalability of qubits in a quantum computing environment. In an implementation, a superconducting amplifier device comprises a parametric amplifier and a tunable coupling between the parametric amplifier and a readout cavity external to the superconducting amplifier device. The tunable coupling allows an entangled signal, associated with a qubit in the readout cavity, to transfer from the readout cavity to the parametric amplifier. The parametric amplifier amplifies the entangled signal to produce an amplified signal as output to a measurement sub-system.

Technology is disclosed herein that the enhances the measurability and scalability of qubits in a quantum computing environment. In an implementation, a superconducting amplifier device comprises a parametric amplifier and a tunable coupling between the parametric amplifier and a readout cavity external to the superconducting amplifier device. The tunable coupling allows an entangled signal, associated with a qubit in the readout cavity, to transfer from the readout cavity to the parametric amplifier. The parametric amplifier amplifies the entangled signal to produce an amplified signal as output to a measurement sub-system.

A superconducting electrical device includes one or more traveling-wave parametric amplifiers (TWPAs) on a chip that is electrically connected to a wiring layer of a substrate. The electrical connection of the chip to the wiring layer of the substrate includes, for each of the one or more TWPAs, a signal bump-bond between the TWPA and the substrate. There is a peripheral ring of ground bumps around the signal bump between the TWPA and the substrate.

A superconducting electrical device includes one or more traveling-wave parametric amplifiers (TWPAs) on a chip that is electrically connected to a wiring layer of a substrate. The electrical connection of the chip to the wiring layer of the substrate includes, for each of the one or more TWPAs, a signal bump-bond between the TWPA and the substrate. There is a peripheral ring of ground bumps around the signal bump between the TWPA and the substrate.

A quantum computing devices includes: a qubit; a readout device coupled to the qubit, the readout device including a frequency filter having a filter frequency range; and an amplifier device coupled to the readout device, in which the amplifier device is configured to amplify a measurement signal from the readout device upon receiving a pump signal having a pump frequency that is outside of the filter frequency range of the frequency filter.

A quantum computing devices includes: a qubit; a readout device coupled to the qubit, the readout device including a frequency filter having a filter frequency range; and an amplifier device coupled to the readout device, in which the amplifier device is configured to amplify a measurement signal from the readout device upon receiving a pump signal having a pump frequency that is outside of the filter frequency range of the frequency filter.

A radio-frequency (RF) to direct current (DC) converter is provided. When a DC electrical current is applied via a DC input port of the converter, the DC electrical current is shunted to ground through a Josephson junction (JJ) of the converter and substantially no DC electrical current flows through a resistor of the converter, and when an RF electrical current is applied via an RF input port of the converter, output trains of SFQ current pulses from a DC to SFQ converter of the RF-to-DC converter with pulse-to-pulse spacing inversely proportional to the RF electrical current frequency cause the JJ to switch at a rate commensurate with an RF frequency of the RF electrical current to generate a steady state voltage across the JJ linearly dependent on the RF frequency.