Darwin could back up his ideas on natural selection by looking at the characteristics of birds and animals. But how can we catch "quantum natural selection" in the act?

In 2007, Wojciech Zurek of the Los Alamos National Laboratory in New Mexico, and his former student, Robin Blume-Kohout of the California Institute of Technology in Pasadena, developed a computer model in which a "quantum pendulum" was set oscillating according to the laws of quantum mechanics. Such an oscillator can exist in a superposition of states, simultaneously present in all possible locations along its path. The duo modeled the environment by including thousands of other pendulums nearby, each "swinging" at a different frequency.

If quantum Darwinism is correct, the environmental pendulums should record a copy of the quantum pendulum’s position. And that is what it did. Multiple copies of the same quantum state were replicated throughout the environment. The model showed quantum Darwinism in action.

In addition, early this year, Roland Brunner of the University of Leoben in Austria and his colleagues showed quantum Darwinism, in theory, in an array of quantum dots—nanoscale bits of semiconducting materials, with electrons that can exist in a superposition of states.

The team studied what happens when multiple dots are arrayed in series and also interact with the environment. They found that two adjacent quantum dots gave rise to a special quantum state that was peculiar to their interaction, and not merely a combination of states of individual quantum dots.

More importantly, they showed that they could find out about these special states by looking at individual quantum dots. It’s as if stable states had been copied and imprinted on all the individual dots. All observers would see the same objective reality—thanks to quantum Darwinism.

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