Google Inc.

Julian Shaw Kelly

Evan Jeffrey

Joshua Yousouf Mutus

Paul Victor Klimov

Kevin Joseph Satzinger

Charles Neill

Alexander Nikolaevich Korotkov

Zijun Chen

Matthew G Neeley

Theodore Charles White

Daniel Thomas Sank

Andrew Lorne Dunsworth

Amit Vainsencher

Rami Barends

Anthony Edward Megrant

Sergio Boixo Castrillo

Vadim Smelyanskiy

Pedram Roushan

Matthew James McEwen

Kostyantyn Yevgenovych Kechedzhi

Juan Carlos Atalaya-Chavez

Christopher Michael Quintana

Paul Klimov

Kevin Satzinger

Andrew Dunsworth

Paul Kimov

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

Methods, systems and apparatus for measuring quantum state purity. In one aspect, a method for determining an average purity of multiple output quantum states, wherein the multiple output quantum states correspond to applications of respective random quantum circuits of a same circuit depth to a same initial quantum state, the method including: obtaining a plurality of data items, wherein each data item corresponds to a respective random quantum circuit of the same circuit depth and represents a probability that application of the respective random quantum circuit to the initial quantum state produces a respective measurement result; calculating a variance of a plurality of data items; determining a Porter-Thomas distribution having a dimension equal to a dimension of each output quantum state; and dividing the calculated variance by a variance of the Porter-Thomas distribution to determine the average purity.

Measuring quantum state purity

Methods and apparatus for generating waveforms for application in a quantum computing device. In one aspect, a system includes a batch generator. The batch generator receives batched waveform data that includes waveform lists, where each waveform list references respective waveform data for unique waveforms in a respective experiment data set that defines a respective experiment. The batch generator further receives a subsequent experiment data set that defines a subsequent experiment. The batch generator determines, based on hardware parameter values included in the subsequent experiment data set, to expand the batched waveform data and expands the batched waveform data to include waveform data of the subsequent experiment data set. Batch instructions that are executable by waveform generator hardware cause the waveform generator hardware, upon execution, to select waveform data referenced in each waveform list and generate a waveform using the selected waveform data.

Batching waveform data

Methods and apparatus for automatic qubit calibration. In one aspect, a method includes obtaining a plurality of qubit parameters and data describing dependencies of the plurality of qubit parameters on one or more other qubit parameters; identifying a qubit parameter; selecting a set of qubit parameters that includes the identified qubit parameter and one or more dependent qubit parameters; processing one or more parameters in the set of qubit parameters in sequence according to the data describing dependencies, comprising, for a parameter in the set of qubit parameters: performing a calibration test on the parameter; and performing a first calibration experiment or a diagnostic calibration algorithm on the parameter when the calibration test fails.

Automatic qubit calibration

Systems and methods for calibrating and initializing a system comprising a first qubit, a second qubit, and a coupler are provided. A method of initializing the system can include calibrating the system; providing a first idle resonance frequency of the first qubit and a second idle resonance frequency of the second qubit; providing the first bias for the first idle resonance frequency and the second bias for the second idle resonance frequency; determining a value of the third resonance frequency at which a difference between the first degree of coupling and the second degree of coupling is minimized, when the first resonance frequency is the first idle resonance frequency and the second resonance frequency is the second idle resonance frequency; and providing the third bias according to the determined value of the third resonance frequency.

Qubit-coupler-qubit model for system calibration

A stacked quantum computing device including a first chip that includes a first dielectric substrate and a superconducting qubit on the first dielectric substrate, and a second chip that is bonded to the first chip and includes a second dielectric substrate, a qubit readout element on the second dielectric substrate, a control wire on the second dielectric substrate, a dielectric layer covering the control wire, and a shielding layer covering the dielectric layer.

Integrating circuit elements in a stacked quantum computing device

Methods, systems and apparatus for benchmarking quantum computing hardware. In one aspect, a method includes defining an initial circuit configured to operate on an array of qubits, wherein the initial circuit comprises multiple instances of the two-qubit gate, wherein each instance of the two-qubit gate performs a same operation on a respective pair of neighboring qubits in the array; partitioning the initial circuit into multiple layers, wherein instances of the two-qubit gate in a respective layer can be implemented in parallel; for each of the multiple layers: constructing benchmarking circuits for the layer, wherein each benchmarking circuit for the layer comprises one or more cycles of quantum gates, each cycle comprising: the layer of instances of the two-qubit gate, and a plurality of single qubit gates; implementing the constructed benchmarking circuits to obtain experimental benchmarking data; and adjusting control parameters of the control model using the experimental benchmarking data.

Parallel cross entropy benchmarking

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

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for parameterization of physical dimensions of discrete circuit components for component definitions that define discrete circuit components. The component definitions may be selected for use in a device design. When a parametrization of a particular version of a discrete circuit component definition is changed, the version level of the device design is also changed and the circuit layout for the device design is physically verified for the new version level.

Integrated circuit design system and method

A device includes a first substrate having a principal surface; a second substrate having a principal surface, in which the first substrate is bump-bonded to the second substrate such that the principal surface of the first substrate faces the principal surface of the second substrate; a circuit element having a microwave frequency resonance mode, in which a first portion of the circuit element is arranged on the principal surface of the first substrate and a second portion of the circuit element is arranged on the principal surface of the second substrate; and a first bump bond connected to the first portion of the circuit element and to the second portion of the circuit element, in which the first superconductor bump bond provides an electrical connection between the first portion and the second portion.

Low footprint resonator in flip chip geometry

Apparatus and methods for performing qubit readout. In one aspect, an apparatus includes a qubit that operates at a qubit frequency; a frequency controller that is configured to control the qubit frequency and that during a qubit measurement operation is configured to: determine a compensation pulse that when applied to the qubit, counteracts qubit frequency changes during the qubit measurement operation; and apply the determined compensation pulse to the qubit during the qubit measurement operation to maintain the qubit frequency.

Compensation pulses for qubit readout

A device includes: a first chip including a plurality of qubits arranged in an array on a first side of the first chip, in which the array includes a plurality of qubit rows and a plurality of qubit columns, in which the plurality of qubits includes a first qubit row including two or more qubits and a second qubit row including two or more qubits, and in which the second qubit row is directly adjacent to the first qubit row; a second chip bonded to the first chip, in which the second chip has a first side that faces the first side of the first chip; a plurality of qubit control elements; a plurality of qubit readout resonators; and a plurality of qubit readout transmission lines.

Scalable quantum processor design

A method comprises causing a plurality of qubit calibration procedures to be performed on one or more qubits in accordance with an automatic qubit calibration process. Log data is stored comprising at least: a record identifying one or more calibration procedures that have been performed, and information relating to the result of the respective calibration procedures. Training data is selected from the log data and is received at a learning module operating at one or more computing devices. A supervised learning model is trained at the learning module to select qubit parameters to be calibrated and/or checked.

Qubit calibration

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.

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Santa Barbara, CA, United States of America

Julian Shaw Kelly