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The world of quantum mechanics is weird. Objects that are far apart can influence each other in what Albert Einstein called “spooky action at a distance”, and cats can potentially be dead and alive at the same time. For decades, scientists have tried to prove that these effects are not just mathematical quirks, but real properties of the physical world.

And they are getting somewhere. Researchers have finally proven in a new study that the link between particles at a distance reflects how the universe behaves, rather than being an experimental artefact. Meanwhile, another team of researchers have set out to show that a living creature, albeit a bacterium, can be in two different quantum states at the same time – just like the cat in Schrödinger’s thought experiment.

Bell’s inequality test

But let’s begin with the paper, published in Nature, which proves that the world is inherently spooky. All systems described by quantum mechanics can display so-called entanglement. For example an […]