Saturday, 02 June, 2012
Quantum interference and phonon-mediated back-action in lateral quantum-dot circuits
G. Granger, D. Taubert, C. E. Young, L. Gaudreau, A. Kam, S. A. Studenikin, P. Zawadzki, D. Harbusch, D. Schuh, W. Wegscheider, Z. R. Wasilewski, A. A. Clerk, S. Ludwig, and A. S. Sachrajda -
Nature Physics, doi:10.1038/nphys2326, published online: 2 June 2012
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 (QPC). It is critical to understand the back-action disturbances resulting from such a measurement approach. Previous studies have indicated that QPC 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 QPC and coherent phonon absorption. Our combined experimental and theoretical results suggest strategies to suppress back-action during the qubit readout procedure.