(Image: Irfan Siddiqi, UC Berkeley)

Can you peek into Schrödinger’s box and catch his cat in the act of existing between the two states of life and death? This multicoloured slinky shows, for the first time, that it’s possible to do just that – except with a qubit quantum circuit instead of a cat.

This image is a map of the random trajectories the quantum state of the qubit takes as it evolves from its initial state to its final one, over many repeated experiments.

Irfan Siddiqi from the University of California, Berkeley, a senior author on the research, calls it “gently recording the cat’s paw prints”.


The work verifies theoretical models of the most likely way in which a quantum system will collapse, proving that the probable path can be predicted. This paves the way to actively controlling a quantum system in the future by steering it towards a certain outcome.

“For example, in chemistry one could use this to prefer certain products of a reaction over others,” says Siddiqi.

So, is the slinky is going up or down the stairs? Obviously, it’s doing both at the same time.

Journal reference: Nature, DOI: 10.1038/nature13559