Quantum Darwinism theory could crack century-long physics conundrum

Quantum Darwinism is a thing; learn more

Ever since Max Planck proposed quantum theory 120 years ago, physicists have tried to reconcile classical physics and quantum physics. The former describes how “large” objects like planets or grains of sand behave. The weird world of quantum mechanics does its best to relate how incredibly small things like atoms and particles interact.

The two branches seemingly operate under very different sets of rules. But now, a fascinating new theory called quantum Darwinism (QD) looks promising in unifying classical and quantum physics, as Futurism reports.

Polish theoretical physicist Wojciech Zurek first posited the theory in 2003. But thanks to recent experiments, QD is now a real contender in explaining how the unreal workings of quantum mechanics can give rise to a tangible universe.

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The Wild World of Quantum Mechanics

One of the wild wonders of quantum theory is superposition. The basic idea behind superposition is that a quantum particle can exist in a variety of quantum states. But this isn’t to say that the particle is in all these states at once.

Think of these superposed states like waves rolling into a rocky beach and interacting with one another. However, once physicists observe the particle, it “appears” in a single state. Think of a single surfer popping up on one of those waves. In other words, the particle moves from the realm of quantum mechanics to the world of classical physics once observed.

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This mind-bending process in which quantum becomes classical is fittingly called decoherence. And QD gives physicists a shot at better understanding it. The theory proposes that it’s not the observation that snaps a particle into one state or another, but rather, it’s the particle’s interactions with the environment that conjures decoherence.

According to QD, that’s why we can’t see everyday objects in their crazy quantum glory: They are always interacting with their environment. It also makes sense, as we know that particles existed before human beings were around to observe them.

“QD putatively explains or helps to explain, all of classicality, including everyday macroscopic objects that aren’t in a laboratory, or that existed before there were any humans,” physicist at the Perimeter Institute for Theoretical Physics, Jess Riedel, told Quanta Magazine.

Survival of the Freakiest

But how does the environment influence the quantum world? Zurek proposes that particles have what he calls “pointer states.” These are measurable properties of a particle, like speed or polarization, that researchers can “point” to with a measuring device. QD theory posits that these pointer states are “selected” by the environment.

Furthermore, only the “fittest” states, ones that can replicate themselves time and again, decohere and offer themselves up for observation. That’s why it’s called quantum Darwinism, referencing Darwin’s famous reference to “survival of the fittest.”

QD theory, like a lot of quantum mechanics, is difficult to wrap the mind around. But Zurek used a good analogy to describe how QD works when speaking with The Foundational Questions Institute in 2008. “The main idea of quantum Darwinism is that we almost never do any direct measurement on anything,” Zurek said. “[The environment] is like a big advertising billboard, which floats multiple copies of the information about our universe all over the place.”

It’s a far-out theory. But the freakiness of the quantum world is what makes it so cool. What matters is that three independent groups of experimental physicists have seemingly held up the theory, as Quanta Magazine detailed. But more experiments must follow to confirm QD. However, there’s a good chance that physicists may have taken the first steps in solving one of the biggest mysteries in modern physics.