What is quantum Darwinism: two physicists of the same universe

When it comes to the physical world, size really matters. While “large” (from a grain of sand to a galactic cluster) objects obey one set of rules that we know from classical physics, “small” objects (atoms and particles) behave completely differently. It was this discovery about 100 years ago that led to the emergence of the discipline, which is now called quantum physics.

Scientists have been looking for a way to reconcile these two disparate physicists for decades. And now the theory, first proposed by the Polish theoretical physicist Wojciech Zurek in 2003, is starting to gain momentum as a potential source of compromise. It's about quantum Darwinism.

One of the unusual aspects of the quantum world is superposition, the ability of a quantum system to exist in more than one state at a time. Apparently, the system goes into one or another state - moving from the quantum world to the "classical" - only at the moment when we observe it. This process is called decoherence, and quantum Darwinism is an attempt to explain it.

Quantum Darwinism suggests that it is the interaction of the system with the environment that causes decoherence, and not the presence of an observer. Proponents of this approach are sure that this point of view explains why we do not see macro objects in a quantum state - they are always subject to environmental factors.

According to Zurek’s theory, quantum systems have “pointer states”. These are specific, measurable characteristics, such as the location or velocity of a particle. When a particle interacts with its surroundings, all superpositions of these characteristics — alternative locations or velocities — decode, leaving only a pointer state that people can observe because it “imprints” itself in the environment.

This is where the idea of ​​Darwinism comes into play: only the “most suitable” state (the most suitable for a given particular environment) experiences the decoherence process. “The basic idea of ​​quantum Darwinism is that we almost never take any direct measurements, ” Zurek said in 2008 at the Institute for Fundamental Issues. “[The environment] is like a large billboard that has numerous copies of information about our universe.”

According to a new article by Quanta Magazine, three separate research groups conducted experiments to test quantum Darwinism in practice and find signs that the quantum system captures replicas of its environment within itself. “All of these studies showed what we expected, at least approximately, ” Zurek said in an interview with Quanta. Probably, we are already on the way to harmonizing the physics of large bodies with the physics of very small ones - we can only wait.

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