When thinking about quantum mechanical systems, single photons and well-isolated ions and atoms may spring to mind, or electrons spreading through a crystal. More exotic in the context of quantum mechanics are genuinely mechanical quantum systems; that is, massive objects in which mechanical motion such as vibration is quantized. In a series of seminal experiments, quintessential quantum-mechanical features have been observed in mechanical systems, including energy quantization and entanglement.
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Source: Phys.org