Jay M. Gambetta

Superconducting qubit in a waveguide cavity with a coherence time approaching 0.1 ms

We report a superconducting artificial atom with a coherence time of

Observation of Berry's Phase in a Solid-State Qubit

{T}_{2}^{*}=92

Scalable and robust randomized benchmarking of quantum processes.

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Protecting superconducting qubits from radiation

s and energy relaxation time

Tunable coupling in circuit quantum electrodynamics using a superconducting charge qubit with a V-shaped energy level diagram.

{T}_{1}=70

Building logical qubits in a superconducting quantum computing system

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Demonstration of Weight-Four Parity Measurements in the Surface Code Architecture

s. The system consists of a single Josephson junction transmon qubit on a sapphire substrate embedded in an otherwise empty copper waveguide cavity whose lowest eigenmode is dispersively coupled to the qubit transition. We attribute the factor of four increase in the coherence quality factor relative to previous reports to device modifications aimed at reducing qubit dephasing from residual cavity photons. This simple device holds promise as a robust and easily produced artificial quantum system whose intrinsic coherence properties are sufficient to allow tests of quantum error correction.

Superconducting qubit with Purcell protection and tunable coupling.

In quantum information science, the phase of a wave function plays an important role in encoding information. Although most experiments in this field rely on dynamic effects to manipulate this information, an alternative approach is to use geometric phase, which has been argued to have potential fault tolerance. We demonstrated the controlled accumulation of a geometric phase, Berrys phase, in a superconducting qubit; we manipulated the qubit geometrically by means of microwave radiation and observed the accumulated phase in an interference experiment. We found excellent agreement with Berrys predictions and also observed a geometry-dependent contribution to dephasing.