I think what they mean is that classical systems use more than a single packet of energy to represent a state. Our “digital systems” are actually analog systems in saturation states. Each time you want to set a bit in memory, you need enough energy to fill up a capacitor (or similar related concept) which is far more than a single electron. This methodology from the viewpoint of quantum systems is repetition/redundancy which provides robustness against stray electrons (eg: from induced current/interference.)

As we build systems that require less power, we are also building systems that use less electrons to represent a single bit.

Another fun tidbit in this space comes down to signal propagation in a lossy medium: we don’t actually use square waves for our clocks since a square wave is composed of many different frequencies. Since different frequencies propagate at different speeds, a square wave looks less and less like a square and also uses more power than a simple sine wave. If you remember your Fourier/Laplace knowledge, you probably remember that a sine is a single frequency and thus it will be coherent through a conductor and use the least amount of power to generate.

Edit: I’m talking about electrons here but the concept of many packets for a single state extends to most of our communication channels today … eg radio communications like we see to/from Voyager.

From, the linked paper:

> This insight captures the essence of Quantum Darwin- ism: Only states that produce multiple informational off- spring – multiple imprints on the environment – can be found out from small fragments of E. The origin of the emergent classicality is then not just survival of the fittest states (the idea already captured by einselection), but their ability to “procreate”, to deposit multiple records – copies of themselves – throughout E

Basically, quantum information is unknown. All possible classical states are mixed together. Once you measure it, it decoheres into a classical system, where all measurements are highly correlated -- some states exist, and others don't exist. A quantum coin flip is heads or tails on top, and tails or heads on bottom. But once you measure it, it all decoheres at once. You get a classical coin flip, that is hrads on top and tails on bottom, or vice versa. You can't get heads on top, and tails or heads on bottom unsettled for a second bit of information. The same message is written twice, on the top and the bottom of the coin. You can look at the top of coin or the bottom and get the same result. If the top of the coin melts, you can still read the result of the flip from the bottom.

All the objective classical facts out there (e.g., the location of the moon, the existence of the dinosaurs, what I ate for breakfast) are recorded in many degrees of freedom (e.g., the photons scattered off the moon, the dinosaur bones, and the microscopic bits of bagel in the trash). By the no-cloning theorem, quantum information cannot be amplified, so this necessarily means the information we can access is classical. But these classical facts are the exception rather than the rule, as far as the full arena of quantum mechanics is concerned. There are always many more degrees of freedom that are not redundantly recorded, for the simple fact that you need to use one degrees of freedom to record another.

Even if the world were fundamentally classical (which it's not), the only things you could actually know about it would be the tiny subset that is amplified to macroscopic scales, necessarily producing many records in, if nothing else, the many atoms in the neurons in your brain.