Spin qubits have been successfully realized in electrostatically defined, lateral few-electron quantum dot circuits. Qubit readout typically involves spin to charge information conversion, followed by a charge measurement made using a nearby biased quantum point contact. It is critical to understand the back-action disturbances resulting from such a measurement approach. Previous studies have indicated that quantum point contact detectors emit phonons which are then absorbed by nearby qubits. We report here the observation of a pronounced back-action effect in multiple dot circuits where the absorption of detector-generated phonons is strongly modified by a quantum interference effect, and show that the phenomenon is well described by a theory incorporating both the quantum point contact and coherent phonon absorption. Our combined experimental and theoretical results suggest strategies to suppress back-action during the qubit readout procedure.
@article{arxiv.1301.7461,
title = {Quantum interference and phonon-mediated back-action in lateral quantum dot circuits},
author = {G. Granger and D. Taubert and C. E. Young and L. Gaudreau and A. Kam and S. A. Studenikin and P. Zawadzki and D. Harbusch and D. Schuh and W. Wegscheider and Z. R. Wasilewski and A. A. Clerk and S. Ludwig and A. S. Sachrajda},
journal= {arXiv preprint arXiv:1301.7461},
year = {2013}
}