The biggest ‘Schrödinger’s cat’ yet — physicists put 7,000 atoms in superposition

Flora Graham

Davide Castelvecchi, Nature magazine

Gary Taubes

Schrödinger's cat has always been an elusive beast, but physicists may have finally trapped one in the laboratory. In the great Austrian physicist's thought experiment, the fate of a cat was linked to the quantum indeterminacy of a radioactive atom—half decayed, half undecayed. The cat, as a result, was both alive and dead. Now physicists at the National Institute of Standards and Technology in Boulder, Colorado, report in this issue ( p. 1131 ) that they have created what one observer calls a “Schrödinger's kitten,” in which they excite an atom into a superposition of quantum states, then ease those two states apart so that the atom appears to be in two distinct physical locations simultaneously.

Colin James

Zhang‐qi Yin, Tongcang Li

The question whether quantum mechanics is complete and the nature of the transition between quantum mechanics and classical mechanics have intrigued physicists for decades. There have been many experimental breakthroughs in creating larger and larger quantum superposition and entangled states since Erwin Schrödinger proposed his famous thought experiment of putting a cat in a superposition of both alive and dead states in 1935. Remarkably, recent developments in quantum optomechanics and electromechanics may lead to the realisation of quantum superposition of living microbes soon. Recent evidence also suggests that quantum coherence may play an important role in several biological processes. In this review, we first give a brief introduction to basic concepts in quantum mechanics and the Schrödinger’s cat thought experiment. We then review developments in creating quantum superposition and entangled states and the realisation of quantum teleportation. Non-trivial quantum effects in photosynthetic light harvesting and avian magnetoreception are also discussed. At last, we review recent proposals to realise quantum superposition, entanglement and state teleportation of micro-organisms, such as viruses and bacteria.

Richard B. Lipkin