The laws of classical and quantum physics differ from each other, but it seems that scientists have finally found a way to bring them together.
When it comes to the physical world, size really does matter. While “large” (from a grain of sand to a galactic cluster) objects obey the same set of rules that we know about from classical physics, “small” objects (atoms and particles) behave quite differently. It was this discovery about 100 years ago that led to the emergence of the discipline that 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 Polish theoretical physicist Wojciech Zurek in 2003, is starting to gain traction 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 state or another - 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 assumes 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 confident 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 environment, all superpositions of these characteristics - alternative locations or velocities - are decohered, leaving only a pointer state that humans can observe because it "imprints" itself into 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 process of decoherence. “The basic idea of quantum Darwinism is that we almost never take any direct measurements,” Zurek said in 2008 at the Institute for Fundamental Questions. "[The environment] is like a big billboard with numerous copies of information about our universe."
According to a new Quanta Magazine article, three separate groups of researchers have conducted experiments to test quantum Darwinism in practice and look for signs that a quantum system is imprinting replicas of its environment within itself. “All of these studies have shown what we expected, at least approximately,” Zurek told Quanta. Probably, we are already on the way to reconcile the physics of large bodies with the physics of very small ones - we just have to wait.
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Vasily Makarov