Quantum interference and phonon-mediated back-action in lateral quantum-dot circuits

You influence a system by measuring it. This back-action is an important consideration when studying tiny structures in which quantum effects play a crucial role. Researchers now show that quantum interference could provide a way to negate back-action in quantum-dot-qubit circuits. Spin qubits have...

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Bibliographic Details
Published in:Nature physics 2012-07, Vol.8 (7), p.522-527
Main Authors: Granger, G., Taubert, D., Young, C. E., Gaudreau, L., Kam, A., Studenikin, S. A., Zawadzki, P., Harbusch, D., Schuh, D., Wegscheider, W., Wasilewski, Z. R., Clerk, A. A., Ludwig, S., Sachrajda, A. S.
Format: Article
Language:English
Subjects:
639/766/483/2802
639/925/357/1017
Absorption
Atomic
Charge
Circuits
Classical and Continuum Physics
Complex Systems
Condensed Matter Physics
Conversion
Disturbances
letter
Mathematical and Computational Physics
Molecular
Nanotechnology
Optical and Plasma Physics
Phonons
Physics
Physics and Astronomy
Quantum dots
Quantum physics
Qubits (quantum computing)
Strategy
Theoretical
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Summary:You influence a system by measuring it. This back-action is an important consideration when studying tiny structures in which quantum effects play a crucial role. Researchers now show that quantum interference could provide a way to negate back-action in quantum-dot-qubit circuits. Spin qubits have been successfully realized in electrostatically defined, lateral few-electron quantum-dot circuits 1 , 2 , 3 , 4 . Qubit readout typically involves spin to charge information conversion, followed by a charge measurement made using a nearby biased quantum point contact 1 , 5 , 6 (QPC). It is critical to understand the back-action disturbances resulting from such a measurement approach 7 , 8 . Previous studies have indicated that QPC detectors emit phonons which are then absorbed by nearby qubits 9 , 10 , 11 , 12 , 13 . 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.
ISSN:1745-2473
1745-2481
DOI:10.1038/nphys2326