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Nano Lett. 2019 Sep 11;19(9):6166-6172. doi: 10.1021/acs.nanolett.9b02207. Epub 2019 Aug 12.

Tunable Coupling of a Double Quantum Dot Spin System to a Mechanical Resonator.

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Naval Research Laboratory , Washington , DC 20375 , United States.
KeyW Corporation , 7740 Milestone Parkway, Suite 150 , Hanover , Maryland 21076 , United States.
NRC Research Associate at the Naval Research Laboratory , Washington , DC 20375 , United States.


The interaction of quantum systems with mechanical resonators is of practical interest for applications in quantum information and sensing and also of fundamental interest as hybrid quantum systems. Achieving a large and tunable interaction strength is of great importance in this field as it enables controlled access to the quantum limit of motion and coherent interactions between different quantum systems. This has been challenging with solid state spins, where typically the coupling is weak and cannot be tuned. Here we use pairs of coupled quantum dots embedded within cantilevers to achieve a high coupling strength of the singlet-triplet spin system to mechanical motion through strain. Two methods of achieving strong, tunable coupling are demonstrated. The first is through different strain-induced energy shifts for the two QDs when the cantilever vibrates, resulting in changes to the exchange interaction. The second is through a laser-driven AC Stark shift that is sensitive to strain-induced shifts of the optical transitions. Both of these mechanisms can be tuned to zero with electrical bias or laser power, respectively, and give large spin-mechanical coupling strengths.


Double quantum dots; cantilever; hybrid quantum systems; optomechanics; spin; strain

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