A team based at the University of Vienna put individual clusters of around 7,000 atoms of sodium metal some 8 nanometres wide into a superposition of different locations, each spaced 133 nanometres apart. Rather than shoot through the experimental set up like a billiard ball, each chunky cluster behaved like a wave, spreading out into a superposition of spatially distinct paths and then interfering to form a pattern researchers could detect. Quantum theory doesn't put a limit on how big a superposition can be, but everyday objects clearly do not behave in a quantum way, she explains. This experiment ' which puts an object as massive as a protein or small virus particle into a superposition ' is helping to answer the 'big, almost philosophical question of 'is there a transition between the quantum and classical''' she says. The authors 'show that, at least for clusters of this size, quantum mechanics is still valid'. The experiment, described in Nature on 21 January1, is of practical...
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