Suppression of photon shot noise dephasing in a tunable coupling superconducting qubit

We demonstrate the suppression of photon shot noise dephasing in a superconducting qubit by eliminating its dispersive coupling to the readout cavity. This is achieved in a tunable coupling qubit, where the qubit frequency and coupling rate can be controlled independently. We observe that the coherence time approaches twice the relaxation time and becomes less sensitive to thermal photon noise when the dispersive coupling rate is tuned from several MHz to 22 kHz. This work provides a promising building block in circuit quantum electrodynamics that can hold high coherence and be integrated into larger systems.Quantum Information: quantum interference suppresses dephasing of qubitsScientists have realized a novel quantum device to improve the robustness of quantum information encoded in a qubit against noise. It is a well known difficulty in quantum information processing that the noise in the environment disturbs the quantum state of a qubit and degrades the qubit's performance. Andrew Houck and colleagues at Princeton University have designed and implemented a superconducting qubit that utilizes the quantum interference effect to decouple itself from microwaves in a nearby cavity. The researchers demonstrate the robust preparation, manipulation and measurement of the qubit in the presence of noise. This approach provides a promising element for the storage and processing of quantum information, mitigating effects of cross-talk when trying to control or measure multiple qubits.