Google Inc.

Kevin Joseph Satzinger

Julian Shaw Kelly

Paul Victor Klimov

Alexander Nikolaevich Korotkov

Charles Neill

Andrew Lorne Dunsworth

Rami Barends

Vadim Smelyanskiy

Zijun Chen

Pedram Roushan

Matthew James McEwen

Kostyantyn Yevgenovych Kechedzhi

Juan Carlos Atalaya-Chavez

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 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

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

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Goleta, CA, United States of America

Kevin Joseph Satzinger