A problem that I have treated in this blog is the question of the quantum-classical transition. This question is hotly debated by people working in quantum optics, quantum computation and wherever foundations of quantum mechanics may enter. Of course, this problem today appears far from being settled and is a heavy burden left us by the fathers of quantum mechanics. Something has been acquired as environmental decoherence. Fighting this effect is a problem experimentalists have today in their everyday activity. But we know that this cannot be all the story.
Some time ago Wojciech Hubert Zurek, one of the main contributors to environmental decoherence, claimed that Hyperion, a Saturn’s moon, behaves classically in its motion just for environmental decoherence otherwise we would observe a macroscopic quantum object splashed in its orbit as happens to electrons in an atom. Of course some people contested these conclusions and come out with a sound explanation of classicality of Hyperion’s motion without the need of environmental decoherence. One of these authors is Leslie Ballentine. I think that a lot of people have read his beautiful book about quantum mechanics. Ballentine and Nathan Wiebe wrote a paper (see here), that went published on Physical Review A (see here), where they soundly proved that Hyperion behaves classically without recurring to any kind of external agent. In some way they gave an hint of an intrinsic emerging of classicality for macroscopic objects (“for all practical purposes” as John Bell taught us). This means that classicality may be an emerging property of quantum objects.
Of course, defenders of environmental decoherence tried to attack Ballentine and Wiebe view (see here). Ballentine’s answer is here. This gives a lucid view of the present criticisms to environmental decoherence, that I would like to recall it is a true observed effect, claiming an intrinsic decoherence effect for isolated quantum systems. The last word has not been said yet. Future experiments will say.
Most of the supporters of environmental decoherence share Ballentine’s views as are well aware of the limitations of this approach. This is part of the truth. I think that here is in view some new deep understanding of how reality forms. Some subtlities are implied and this can explain difficulties researchers have currently met.