Google Inc.

Paul Victor Klimov

Julian Shaw Kelly

Alexander Nikolaevich Korotkov

Kevin Joseph Satzinger

Rami Barends

Anthony Edward Megrant

Vadim Smelyanskiy

Evan Jeffrey

Daniel Thomas Sank

Charles Neill

Zijun Chen

Matthew James McEwen

Amit Vainsencher

Juan Carlos Atalaya-Chavez

Christopher Michael Quintana

Methods, systems, and apparatus for determining frequencies at which to operate interacting qubits arranged as a two dimensional grid in a quantum device. In one aspect, a method includes the actions of defining a first cost function that characterizes technical operating characteristics of the system. The cost function maps qubit operation frequency values to a cost corresponding to an operating state of the quantum device; applying one or more constraints to the defined first cost function to define an adjusted cost function; and adjusting qubit operation frequency values to vary the cost according to the adjusted cost function such that the operating state of the quantum device is improved.

Optimizing qubit operating frequencies

A quantum computing device includes: a qubit; a single XYZ control line, in which the qubit and the single control line are configured and arranged such that, during operation of the quantum computing device, the single XYZ control line allows coupling of an XY qubit control flux bias, from the single XYZ control line to the qubit, over a first frequency range at a first predetermined effective coupling strength, and coupling of a Z qubit control flux bias, from the single XYZ control line to the qubit, over a second frequency range at a second predetermined effective coupling strength.

Single line qubit control

Systems and methods for measuring quantum states of qubits with more than two levels are provided. A method can include, for a plurality of shuffling sequences, applying, by a quantum computer, one or more quantum gates to the one or more qubits to execute a quantum algorithm; applying, by the quantum computer, a shuffling sequence to the one or more qubits; and measuring, using a readout apparatus, the state of the one or more qubits to determine a readout state. The method can further include determining, by a classical computer or the quantum computer, an average occupation for one or more of the quantum states of the one or more qubits using the readout states for each of the shuffling sequences. The readout states can correspond to a state in a subset of the quantum states of the one or more qubits.

Multi-state qubit readout with permutation sequences

Systems and methods for operating one or more qubits in a quantum computing system are provided. In some examples, a method can include obtaining past time data associated with a temporal metric of an operating parameter of a qubit in a quantum device. The method can include selecting an operating parameter value based at least in part on the past time data associated with the temporal metric of the operating parameter to reduce likelihood of occurrence of a time dependent defect. The time dependent defect can exhibit a time dependent behavior. The method can include operating the qubit in the quantum device at the operating parameter value.

Operating quantum devices using a temporal metric

A quantum computing system configured for removal of leakage states can include quantum hardware including a first qubit and a second qubit, wherein the first qubit is configured to have a first transition frequency and wherein the second qubit is configured to have a second transition frequency, the first transition frequency being greater than the second transition frequency. The quantum computing system can include one or more quantum control devices configured to control operation of at least the first qubit and the second qubit, wherein the one or more quantum control devices are configured to implement a quantum gate operation on the first qubit and the second qubit based at least in part on the first transition frequency and the second transition frequency, and wherein the one or more quantum control devices are configured to periodically reset a quantum state of the first qubit.

Frequency configuration in quantum gates for leakage removal

A computer-implemented method for refining a qubit calibration model is described. The method comprises receiving, at a learning module, training data, wherein the training data comprises a plurality of calibration data sets, wherein each calibration data set is derived from a system comprising one or more qubits, and a plurality of parameter sets, each parameter set comprising extracted parameters obtained using a corresponding calibration data set, wherein extracting the parameters includes fitting a qubit calibration model to the corresponding calibration data set using a fitter algorithm. The method further comprises executing, at the learning module, a supervised machine learning algorithm which processes the training data to learn a perturbation to the qubit calibration model that captures one or more features in the plurality of calibration data sets that are not captured by the qubit calibration model, thereby to provide a refined qubit calibration model.

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Santa Barbara, CA, United States of America

Paul Victor Klimov