Chad Rigetti

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

RF-Driven Josephson Bifurcation Amplifier for Quantum Measurement

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

Protecting superconducting qubits from radiation

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Simple all-microwave entangling gate for fixed-frequency superconducting qubits.

s and energy relaxation time

Measuring the decoherence of a quantronium qubit with the cavity bifurcation amplifier

{T}_{1}=70

Protocol for Universal Gates in Optimally Biased Superconducting Qubits

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Characterization of addressability by simultaneous randomized benchmarking

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.

Entanglement of two superconducting qubits in a waveguide cavity via monochromatic two-photon excitation

We have constructed a new type of amplifier whose primary purpose is the readout of superconducting quantum bits. It is based on the transition of a rf-driven Josephson junction between two distinct oscillation states near a dynamical bifurcation point. The main advantages of this new amplifier are speed, high sensitivity, low backaction, and the absence of on-chip dissipation. Pulsed microwave reflection measurements on nanofabricated Al junctions show that actual devices attain the performance predicted by theory.