Quantum physics has always been a source of mystery and delight. It is mysterious because it defies common sense: a world where atoms exist in two places at once, cats are simultaneously dead and alive, and particles exhibit a strange kind of telepathy. It is a delight because we have learned to manipulate these strange phenomena. We can perform experiments and build technologies that seem fantastical and impossible, but allow us to explore the very roots of reality.

The weirdness of the quantum world led some of our foremost intellects - Einstein included - to conclude that we must somehow have got it wrong. After all, it defies all our notions of space and time. It reveals all the world’s processes to be random at heart. It tells us that the atoms in our bodies inhabit a reality that is utterly alien to our everyday experience. But we now know these are not mistaken ideas; they are proven, and have real, practical consequences.

This issue of New Scientist: The Collection will lay out the ideas, the unresolved paradoxes and puzzles, and the myriad uses of quantum theory. From parallel universes to photosynthesis, from entanglement to encryption, from computing to cats, the quantum world offers an unparalleled universe of phenomena to explore and enjoy.