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Dynamics of a qubit while simultaneously monitoring its relaxation and dephasing

Authors: Ficheux, Q. and Jezouin, S. and Leghtas, Z. and Huard, B., Nature Communications, Vol 9, No 1926, May 2018, DOI: 10.1038/s41467-018-04372-9
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Decoherence originates from the leakage of quantum information into external degrees of freedom. For a qubit, the two main decoherence channels are relaxation and dephasing. Here, we report an experiment on a superconducting qubit where we retrieve part of the lost information in both of these channels. We demonstrate that raw averaging the corresponding measurement records provides a full quantum tomography of the qubit state where all three components of the effective spin-1/2 are simultaneously measured. From single realizations of the experiment, it is possible to infer the quantum trajectories followed by the qubit state conditioned on relaxation and/or dephasing channels. The incompatibility between these quantum measurements of the qubit leads to observable consequences in the statistics of quantum states. The high level of controllability of superconducting circuits enables us to explore many regimes from the Zeno effect to underdamped Rabi oscillations depending on the relative strengths of driving, dephasing, and relaxation.
author = {Q. and Jezouin Ficheux, S. and Leghtas, Z. and Huard, B.},
title = {Dynamics of a qubit while simultaneously monitoring its relaxation and dephasing},
journal = {Nature Communications},
volume = {9},
number = {1926},
pages = {},
year = {2018},