Google Inc.

Charles Neill

Anthony Edward Megrant

Julian Shaw Kelly

Yu Chen

Kevin Joseph Satzinger

Kostyantyn Yevgenovych Kechedzhi

Andrew Lorne Dunsworth

Rami Barends

Vadim Smelyanskiy

Evan Jeffrey

Zhang Jiang

Daniel Thomas Sank

Yuezhen Niu

Paul Victor Klimov

Alexander Nikolaevich Korotkov

Pedram Roushan

Amit Vainsencher

Christopher Michael Quintana

Xiao Mi

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

Systems and methods for composite quantum gate calibration for a quantum computing system are provided. In some implementations, a method includes accessing a unitary gate model describing a composite quantum gate. The unitary gate model includes a plurality of gate parameters. The method includes implementing the composite quantum gate for a plurality of gate cycles on the quantum system to amplify the plurality of gate parameters. The method includes obtaining a measurement of a state of the quantum system after implementing the composite quantum gate for the plurality of gate cycles. The method includes determining at least one of the plurality of gate parameters based at least in part on the measurement of the state of the quantum system. The method includes calibrating the composite quantum gate for the quantum computing system based at least in part on the plurality of gate parameters.

Composite quantum gate 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

Methods, systems and apparatus for implementing two-qubit gates using a tunable coupler. In one aspect, a method of implementing a two-qubit gate includes: applying a unitary transformation control signal to a tunable coupler arranged between a first data qubit and a second data qubit to obtain a target unitary transformation of the first data qubit and the second data qubit, wherein the unitary transformation control signal is applied to the tunable coupler over a predetermined period of time to allow coupling between the first data qubit and the second data qubit through the tunable coupler.

Two-qubit gates implemented with a tunable coupler

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

Methods, systems and apparatus for implementing a tunable qubit coupler. In one aspect, a device includes: a first data qubit, a second data qubit, and a third qubit that is a tunable qubit coupler arranged to couple to the first data qubit and to couple to the second data qubit such that, during operation of the device, the tunable qubit coupler allows tunable coupling between the first data qubit and the second data qubit.

Tunable qubit coupler

Methods, systems and apparatus for implementing a target two-qubit quantum logic gate on a first qubit and second qubit using a tunable qubit coupler. In one aspect, a method includes generating a control signal for the target two-qubit quantum logic gate according to a control model, wherein the control model comprises a controlled-Z operator and a swap operator that are non-orthogonal; and applying the control signal to the first qubit, second qubit and tunable qubit coupler.

Frequency tunable qubit control strategy

Growing community of inventors

Goleta, CA, United States of America

Charles Neill