An electron, atom, or other quantum system can be many places at once. It collapses into a single location when an observer pinpoints it, but what happens when an object is not being measured? Can it choose a location on its own, or must it wait for an observer?
SFI External Professor Wojciech Zurek might have an answer.
His Theory of Quantum Darwinism applies natural selection to our quantum universe. It builds on the theory of decoherence, which shows that a quantum particle can no longer be in many places at once not only at the moment it’s measured, but also when it interacts with its environment, which can be a de facto observer. (For a particle, common environments are photons and air molecules. Scaling up to a more tangible level, our world persists in its classical state only because large objects can never be fully isolated from their surroundings.)
Quantum Darwinism goes beyond decoherence by studying imprints left by the system on the environment, he says. Drawing from natural selection, where the fittest survive and proliferate, Quantum Darwinism shows that certain states are selected because they survive better than others in a given environment.
Surviving states then proliferate by spreading information about themselves, and we discover them indirectly by intercepting tiny fractions of the environment. This is how consensus about the fittest states -- the “objective classical reality” we take for granted -- arises in our quantum universe, Zurek says, and how effectively classical states that exist objectively, immune to measurement, emerge from a quantum substrate.
Recent studies have offered evidence in support of Zurek’s theory. Now, with his newly awarded grant from the John Templeton Foundation, he will examine how quantum information propagates, and how the classical world of our everyday experience emerges from the quantum ingredients.
Read the article in the SFI Update (September/October 2011)
Read the Naturepaper on Quantum Darwinism (March 2009)
More about Quantum Darwinism