Google Inc.

Zijun Chen

Julian Shaw Kelly

Rami Barends

Vadim Smelyanskiy

Sergio Boixo Castrillo

Daniel Thomas Sank

Paul Victor Klimov

Kevin Joseph Satzinger

Alexander Nikolaevich Korotkov

Matthew James McEwen

Juan Carlos Atalaya-Chavez

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, systems, and apparatus for measuring the dispersive shift or linewidth of a resonator coupled to a qubit. In one aspect, a method includes the actions of: generating resonator response data, comprising, for each of two computational states of the qubit: for each of multiple qubit drive frequencies: for each of multiple resonator drive frequencies: preparing the qubit in the computational state; applying a first drive pulse with the resonator drive frequency to the resonator, applying a second drive pulse with the qubit drive frequency to the qubit; measuring the state of the qubit; and processing the generated resonator response data to determine the dispersive shift or linewidth of the resonator.

Probe of qubit-resonator dispersive shift using ac stark shift

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 device includes: a plurality of qubits arranged in a two-dimensional array and a plurality of readout resonators. Each readout resonator of a first readout resonator group is arranged to electromagnetically couple to a respective qubit of a first qubit group. Each readout resonator of a second readout resonator group is arranged to electromagnetically couple to a respective qubit of a second qubit group. A resonance frequency of each readout resonator of the first readout resonator group is within a first resonance frequency band, and a resonance frequency of each readout resonator of the second readout resonator group is within a second resonance frequency band that is different from the first resonance frequency band.

Frequency placement for qubit readout resonators

Growing community of inventors

Santa Barbara, CA, United States of America

Zijun Chen