Quantum Darwinism, an Idea to Explain Objective Reality, Passes First Tests

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sciborg2

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« on: July 22, 2019, 04:49:29 pm »
Quantum Darwinism, an Idea to Explain Objective Reality, Passes First Tests

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One of the most remarkable ideas in this theoretical framework is that the definite properties of objects that we associate with classical physics — position and speed, say — are selected from a menu of quantum possibilities in a process loosely analogous to natural selection in evolution: The properties that survive are in some sense the “fittest.” As in natural selection, the survivors are those that make the most copies of themselves. This means that many independent observers can make measurements of a quantum system and agree on the outcome — a hallmark of classical behavior.

This idea, called quantum Darwinism (QD), explains a lot about why we experience the world the way we do rather than in the peculiar way it manifests at the scale of atoms and fundamental particles. Although aspects of the puzzle remain unresolved, QD helps heal the apparent rift between quantum and classical physics.

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About a decade ago, while Riedel was working as a graduate student with Zurek, the two showed theoretically that information from some simple, idealized quantum systems is “copied prolifically into the environment,” Riedel said, “so that it’s necessary to access only a small amount of the environment to infer the value of the variables.” They calculated that a grain of dust one micrometer across, after being illuminated by the sun for just one microsecond, will have its location imprinted about 100 million times in the scattered photons.

It’s because of this redundancy that objective, classical-like properties exist at all. Ten observers can each measure the position of a dust grain and find that it’s in the same location, because each can access a distinct replica of the information. In this view, we can assign an objective “position” to the speck not because it “has” such a position (whatever that means) but because its position state can imprint many identical replicas in the environment, so that different observers can reach a consensus.

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Horodecki and other theorists have also sought to embed QD in a theoretical framework that doesn’t demand any arbitrary division of the world into a system and its environment, but just considers how classical reality can emerge from interactions between various quantum systems. Paternostro says it might be challenging to find experimental methods capable of identifying the rather subtle distinctions between the predictions of these theories.

Still, researchers are trying, and the very attempt should refine our ability to probe the workings of the quantum realm. “The best argument for performing these experiments probably is that they are good exercise,” Riedel said. “Directly illustrating QD can require some very difficult measurements that will push the boundaries of existing laboratory techniques.” The only way we can find out what measurement really means, it seems, is by making better measurements.
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mostly.harmless

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« Reply #1 on: September 01, 2019, 12:06:00 pm »
Thanks for sharing. Fascinating stuff.

I don't get how a dust mote can impose its position at other locations? The example helps me to grasp a bit better what it is that QD is trying to explain, but I failed to observe (or skimmed to quickly through the article) how that is actually 'calculated', as the article states.

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sciborg2

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« Reply #2 on: September 01, 2019, 02:22:35 pm »
Thanks for sharing. Fascinating stuff.

I don't get how a dust mote can impose its position at other locations? The example helps me to grasp a bit better what it is that QD is trying to explain, but I failed to observe (or skimmed to quickly through the article) how that is actually 'calculated', as the article states.

Yeah it's a bit confusing, and the author does admit there are deep questions that need to be answered in his paper:

https://arxiv.org/pdf/0903.5082.pdf

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In the end one might ask: “How Darwinian is Quantum Darwinism?”. Clearly, there is survival of the fittest,and fitness is defined as in natural selection – through the ability to procreate. The no-cloning theorem implies competition for resources – space in [E]– so that only pointer states can multiply (at the expense of their complementary competition). There is also another aspect of this competition: Huge memory available in the Uni-verse as a whole is nevertheless limited. So the question arises: What systems get to be “of interest”, and imprint their state on their obliging environments, and what are the environments? Moreover, as the Universe has a finite memory, old events will be eventually “overwritten” by new ones, so that some of the past will gradually cease to be reflected in the present record. And if there is no record of an event, has it really happened? These questions seem far more interesting than deciding closeness of the analogy with natural selection [40]. They suggest one more question: 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?
« Last Edit: September 01, 2019, 02:24:44 pm by sciborg2 »
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mostly.harmless

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« Reply #3 on: September 01, 2019, 06:21:57 pm »
Thanks sciborg2, I missed that.
Bookmarked the PDF to my ever increasing to-read list.. I need a reading holiday.

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