Quantum Darwinism can explain the nature of classical reality. But is it really a form of natural selection or just an imposter?
Quantum darwinism is an extraordinary idea that was unleashed last year by the physicist by Wojciech Zurek at Los Alamos National Labs in New Mexico.
It's main claim is that it explains the quantum-classical transition: why macroscopic physics obeys classical rules while the quantum world obeys the seemingly weird laws of quantum mechanics. That makes it a Big Idea.
So how does it work? Zurek's way into this problem is to think about the role of the environment in quantum mechanics. For other quantum physicists, the environment has never been anything more than a nuisance. Consider a quantum object in isolation and the quantum information it contains can survive forever. But place it in the real world and this quantum information leaks into the environment, destroying the system under study.
Zurek takes different view. He thinks of the environment as an information channel and the properties of this channel are the key to understanding quantum darwinism.
All macroscopic measuring machines get their information through this channel. For example, at this very moment you are intercepting a fraction of the photons emitted by a screen. But we can never observe all of the environment, only a small fraction of it which reveal systems of interest.
This is the essence of quantum darwinism, says Zurek. Only quantum states that can be transmitted through the environment in the right kind of way and with multiple copies, can be observed on the macroscopic scale. That rules out various kinds of quantum information. What's left are what Zurek calls "pointer states". These are what we observe classically.
So the classical view of the universe is determined by the states that survive transmission through the environmental information channel. Hence the darwinism: it is only possible to observe the states that are fit enough to survive this process of transmission.
But is this real survival of the fittest or just something like it? That's the question raised today by the independent researcher John Campbell.
It has long been known that Darwin's theory of natural selection can be applied in many situations. The "substrate free" version of it is called universal darwinism and is essentially an algorithm composed of three steps: replication or copying, variations amongst the copies, and selective survival of the copies determined by which variations they possess.
Campbell's conclusion is that quantum darwinism meets this criteria.
That still leaves many questiosn unanswered, of course. In his paper introducing quantum darwinism, Zurek asks: "Is Quantum Darwinism (a process of multiplication of information about certain favored states that seems to be a fact of quantum life") in some way behind the familiar natural selection? I cannot answer this question, but neither can I resist raising it."
Campbell would have us believe that they are intimately linked, although this conclusion is by no means a slam dunk.
There's plenty of inspiring work to be done here by any philosophers with a little time on their hands.
Ref: arxiv.org/abs/1001.0745: Quantum Darwinism as a Darwinian process