Abstract: A system, comprising a superconducting integrated circuit and a controller, may be operated to apply, for each power level of a sequence of discrete power levels on a respective one of a plurality of power lines, one or more pulses via a respective one of a plurality of addressing lines to a respective compound Josephson junction of each of a plurality of flux storage devices of the superconducting integrated circuit to cause each of the plurality of flux storage devices to reset. Power levels may be based at least in part on an estimated worst-case asymmetry between Josephson junctions of the compound Josephson junctions. The system may be operated to partition the plurality of addressing lines into groups, and apply a respective sequence of pulses to each addressing line of each pairwise combination of groups to cause one or more of the plurality of flux storage devices to reset.

Abstract: Methods and systems for calibrating quantum processors are discussed. A model of a portion of the processor to be calibrated has one or more determinable parameters and an uncertainty for the determinable parameter(s). A measurement procedure is iteratively performed by selecting a subset of possible measurements and generating predicted measurement outcomes and predicted uncertainties for the determinable parameter for each measurement in the subset of possible measurements. Based on the predicted reduction in uncertainty for the determinable parameter, one or more measurements is selected. Instructions are transmitted to the quantum processor to perform the selected measurements, and the results are returned to update the model of the portion of the processor to be calibrated. Once a termination criteria is met, a calibrated value is generated for the determinable parameter. Compensating signals can be applied to devices of the quantum processor to calibrate the devices.

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 digital processor simulates a quantum computing system by implementing a QPU model including a set of representation models and a device connectivity representation to simulate a quantum processor design or a physical quantum processor. The digital processor receives an analog waveform and generates a digital waveform representation comprising a set of waveform values that correspond to biases applied to programmable devices in a quantum processor. The digital processor selects a subset of waveform values based on channels in the device connectivity representation. The digital processor implements a representation model to compute a response based on the waveform values and a plurality of physical parameter values, the physical parameters characterizing a programmable device in a quantum processor.

Abstract: A hybrid processor includes a classical (digital) processor and a quantum processor and implements a calibration procedure to calibrate devices in the quantum processor. Parameter measurements are defined as vertices in a directed acyclic graph. Dependencies between measurements are defined as directed edges between vertices. The calibration procedure orders the vertices, respecting the order of the dependencies while at least attempting to reduce the time needed to perform all the measurements. The calibration procedure provides a level of abstraction to allow non-expert users to use the calibration procedure. Each vertex has a set of attributes defining the status of the measurement, time of the measurement and value of the measurement.

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 hybrid processor includes a classical (digital) processor and a quantum processor and implements a calibration procedure to calibrate devices in the quantum processor. Parameter measurements are defined as vertices in a directed acyclic graph. Dependencies between measurements are defined as directed edges between vertices. The calibration procedure orders the vertices, respecting the order of the dependencies while at least attempting to reduce the time needed to perform all the measurements. The calibration procedure provides a level of abstraction to allow non-expert users to use the calibration procedure. Each vertex has a set of attributes defining the status of the measurement, time of the measurement and value of the measurement.