<!--intro-->Scientists have recreated the weirdness of the quantum world on a real-world scale. This macroscopic quantum object is a loop in which current flows in opposite directions at the same time.<!--/intro--> <center ><a HREF='http://www.newscientist.com/'><img SRC='http://www.newscientist.com/ads/people_why.gif' BORDER=0></a></center> A group based at the State University of New York in Stony Brook made similar observations in July. But Caspar van der Wal at the Delft University of Technology in the Netherlands says his observations are in some ways a more striking example of a macroscopic object being in two different quantum mechanical states at the same time. Van der Wal, who leads the group, says his creation is a step towards the goal of building circuitry for a quantum computer. "We've shown how to control decoherence to some extent," he says. Decoherence occurs in a quantum system when it is disturbed by noise, leading to the loss of information carried in the system's wave function. <b>Running in circles</b> In Van der Wal's experiment, microwaves were applied to an aluminium superconducting loop to encourage tunnelling between two low-energy quantum states. In one state the current runs clockwise, in the other it runs anticlockwise. The challenge for the researchers was to measure the oscillating current without disturbing the system enough to trigger decoherence. Van der Wal went further than the Stony Brook group in obtaining the first tentative measurements of decoherence time - the time it takes for noise in the environment to destroy the loop's quantum mechanical state. Although the loop is only a micrometre across, it is made of tens of billions of aluminium atoms, making it huge in quantum mechanical terms. It is the closest physicists have come to creating Schrödinger's cat, a thought experiment in which a cat's life depends on a chancy quantum mechanical event, condemning it to a superposition of being dead and alive at the same time.