LAUSR

According to quantum mechanics, a physical system can be in any linear superposition of its possible states. Although the validity of this principle is routinely validated for microscopic systems, it is still unclear why we do not observe macroscopic objects to be in superpositions of states that can be distinguished by some classical property. Here we demonstrate the preparation of a mechanical resonator in Schrödinger cat states of motion, where the ∼1017 constituent atoms are in a superposition of two opposite-phase oscillations. We control the size and phase of the superpositions and investigate their decoherence dynamics. Our results offer the possibility of exploring the boundary between the quantum and classical worlds and may find applications in continuous-variable quantum information processing and metrology with mechanical resonators. Description Schrodinger’s cats, kittens, and lions The idea of Schrodinger’s cat being both alive and dead at the same time—its fate revealed only upon inspection—came from a thought experiment that pointed out an absurdity in the interpretation of quantum mechanics at the time. However, because such superposition states have now been prepared in many different quantum systems, the question is where do the classical and quantum worlds part company? Bild et al. prepared, observed, and controlled cat states of a 16-microgram mechanical resonator. Being able to control the size of the superposition states, they effectively created a menagerie of quantum states, thus providing a platform to explore the boundary between the quantum and classical behavior. —ISO The collective motion of about 1017 atoms was prepared in quantum superpositions of macroscopically distinct states.