Google Inc.

Daniel Thomas Sank

Julian Shaw Kelly

John Martinis

Yu Chen

Alireza Shabani Barzegar

Evan Jeffrey

Ofer Naaman

Rami Barends

Anthony Edward Megrant

Theodore Charles White

Paul Victor Klimov

Charles Neill

Zijun Chen

Kevin Chenghao Miao

Amit Vainsencher

Nicholas Reinhard Zobrist

Alexander Matthew Opremcak

Christopher Michael Quintana

Paul Kimov

A quantum computing system includes a cryogenic chamber and an integrated circuit located in the chamber. The integrated circuit includes a substrate, a qubit formed on the substrate, and a dissipative element that is formed on the substrate and coupled to the qubit. When the qubit is tuned to a first flux value, the integrated circuit is enabled to perform quantum-computation operations on a set of quantum states of the qubit. The quantum states include a ground state and an excited state. When the qubit is tuned to a second flux value, the qubit is enabled to transfer energy associated with the excited state from the qubit to the dissipative element. Upon the energy transfer, the qubit is transitioned to the ground state. The dissipative element is enabled to dissipate the transferred energy to a portion of the substrate.

Resetting quantum states of qubits via on-chip lossy resonators within quantum computing systems

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

This disclosure is directed to a quantum computing system (QCS) that includes a cryogenic sub-system, a signal-generating element, a first signal-splitting element, a first transmission path, a second transmission path, a third transmission path, and a quantum device. A first environment is located outside the cryogenic sub-system and a second environment is associated with the cryogenic sub-system. The signal-generating element generates a first signal. The first signal-splitting element is positioned within the second environment. The quantum device is positioned within the cryogenic sub-system. The first transmission path transmits the first signal from the signal-generating element to the first signal-splitting element. The first signal-splitting element subdivides the first signal into a second signal and a third signal. The third transmission transmits the third signal from the first signal-splitting element to the first environment. The second transmission path transmits the second signal from the first signal-splitting element to the quantum device.

Thermalization and attenuation of signals within quantum computing systems via directional couplers

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

Systems and methods for balanced inductive and capacitive coupling for quantum circuits are provided. A quantum circuit can include a qubit structure comprising an inductor and at least a first portion of a qubit capacitor. The quantum circuit can further include a ground, and a second portion of the qubit capacitor coupled to the ground. The quantum circuit can further include a readout resonator configured to measure a state of the qubit structure. The quantum circuit can further include a capacitive coupling between the readout resonator and the qubit structure and an inductive coupling between the readout resonator and the inductor of the qubit structure. A coupling strength of the inductive coupling and a coupling strength of the capacitive coupling can be approximately equal in magnitude.

Balanced inductive and capacitive resonator coupling for quantum computing system

A qubit device includes an elongated thin film uninterrupted by Josephson junctions, a quantum device in electrical contact with a proximal end of the elongated thin film, and a ground plane that is co-planar with the elongated thin film and is in electrical contact with a distal end of the elongated thin film, in which the thin film, the quantum device, and the ground plane comprise a material that is superconducting at a designed operating temperature.

Co-planar waveguide flux qubits

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.

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Mountain View, CA, United States of America

Daniel Thomas Sank