The invisible (?) quantum world

The word quantum, and the weirdness of phenomena that Quantum Mechanics (QM) successfully describes, fascinate many a writer and thinker outside the physics community; every now and then, some of them attempt to establish improbable parallels between experimentally observable effects that occur at the atomic and subatomic level (such as entanglement) and their quantum-mechanical theoretical interpretation, and aspects of our daily experience in which QM most likely does not belong, such as the workings of the human mind, the existence of parallel universes, body healing… you name it.

To be sure, respectable theoretical inquiries into the quantum-mechanical foundation of human consciousness1,2, for example, or into the relationship between QM and the biological underpinnings of life3, can be found in the scientific literature. For the most part, however, positing connections of QM with things such as free will, mysticism etc., is an exercise in vacuity, almost invariably played out in media outside mainstream science, involving authors with no actual knowledge of QM and at best a rudimentary understanding of how science works. A number of science bloggers have already extensively documented (and eloquently commented upon) such a nonchalant, inaccurate and misleading use of the word “quantum”, and the ensuing misrepresentation of QM and overall disservice of this practice to science popularization.
While QM, as a more fundamental theory, must ultimately underlie any macroscopic phenomenon, Classical Mechanics (CM), which is based on a radically different formalism than QM and whose connection with QM is fairly subtle (uncomfortably tenuous to many of us, actually), is better suited at describing phenomena that occur at length scales and temperatures relevant to human life and experience, including most biological processes. A direct and unambiguous observation of a genuinely quantum-mechanical effect generally involves performing experiments at the atomic or sub-atomic scale and/or at temperatures much lower than those at which life (as we presently know it) can exist.

However, the above does not mean that effects and consequences of QM are “unobservable in principle” at room temperature and on a macroscopic scale. Blanket statements of this type, sometimes made even by physicists, constitute exaggerations in the opposite direction, are plainly untrue (or at least awfully simplistic), and risk generating as much confusion as the naive extrapolation of notions derived from QM to realms where they do not and cannot apply.
Perhaps the simplest example of QM “in action”, one with which we are all familiar, is the existence of permanent magnets (yes, the ones that stick to the fridge door). Indeed, one may well argue that ferromagnetism, observable in big chunks of iron at room temperature and above, is no less impressive a manifestation of QM on a macroscopic scale than superconductivity, the latter being regarded as more “exotic” merely because it is not part of our daily experience, and not observed as easily.
Plank’s law of black-body radiation, whose formulation is widely regarded as the birth of QM, has a number of macroscopic implications and practical applications, even in Astrophysics, far away from the “cold and small” limits to which QM is supposedly restricted.
Other effects of quantum mechanics can indeed be detected directly and unambiguously at room temperature, upon performing appropriate experiments; and while some of these experiments involve particular types of materials and/or somewhat unusual physical conditions (e.g., very high pressure), others can be relatively easily carried out on ordinary matter (e.g., metals)[0].
Granted, one is not talking about experiments that most people can, or will carry out; whether that means that QM is further removed from one’s daily life than other scientific theories, is largely a matter of personal taste. It is true that most of us can and do go through life without been directly exposed to much QM; likewise, most of us can and do go through life without ever observing a biological cell through a microscope, or being bitten by a black widow, or visiting the South Pole, which does not certainly make any of these things “unobservable”.

Now, one could argue that the quantum-mechanical effects described above are not the jaw-dropping type, weirder displays of quantum behavior that capture the imagination of science fiction writers and new-age thinkers. Those manifestations (unlike the ones mentioned above) hinge on the onset of coherence, which is one of the most profound and elusive concepts arising within QM, describing essentially a state of high coordination involving several identical particles. In order for coherence to be established over a sample of matter large enough to be observable by naked eye (thus comprising a number of particles as large as 1023), stringent physical requirements must be met, something that does not normally occur at “ordinary” conditions of temperature and pressure. Furthermore, coherence is very delicate, easily destroyed by the interaction of the system with its surroundings, which is why the experimental observation of those spectacular, macroscopic manifestations of QM (such as superconductivity) typically requires highly controlled experimental settings, in particular very low temperature.
Here too, however, drastic expressions of skepticism about the possibility of observing such phenomena at room temperature seem unjustified, given the current state of knowledge. Consider superconductivity, for example. True, the highest superconducting transition temperature reported to date is 164 K (-164 F or -109 oC), which is nowhere near room temperature. Still, it is much higher than what was believed to be the theoretical upper bound prior to 1986. More importantly, there is really no fundamental reason (at least none currently known) why room temperature superconductors ought not exist, hence the ongoing, still vigorous experimental and theoretical effort aimed at identifying potential materials and/or physical systems that could undergo a superconducting transition at room temperature.
Advances in materials science are making it feasible to observe at room temperature quantum-mechanical effects long thought of as only detectable at very low temperature, such as the Quantum Hall effect, for which coherence indeed plays an important role. Does it really seem so far-fetched to imagine that, some day in the not-so-distant future, devices based on room-temperature superconductivity for example, may be as familiar as, well, refrigerator magnets ? Of course, optimism can come in different degrees, but I tend to believe that, fifty years from now, QM will be much more a part of one’s daily experience than it is now.

Will we live to see the day when we can be quantum teleported to some other universe ? I would not bet on that. Likewise, expressions such “entanglement of minds” will likely remain forever a figure of speech, and the quantum-mechanical underpinnings of physical attraction between two people will probably never be discovered. At the same time, the notion that QM is confined to phenomena occurring at the atomic and subatomic level, bearing little or no relevance to anything taking place at length scales and temperatures relevant to human experience seems also inaccurate.

[0] One of the most remarkable results of QM is accounting for the experimentally observed electronic contribution to the specific heat of metals at room temperature, based on the free electron model, for which a treatment based on classical physics yields inaccurate predictions.

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