Purifying Physics: The quest to explain why the “quantum” exists
plus.maths.org
plus.maths.org
One can shrug and say, we know what we need for computations. But a fairly fundamental theory should be cleaner. Of course, there is a perfectly simple theory (Bohm's) involving Schrodinger's equation and a guiding equation for particles that has all of this quantum formalism derivable from its dynamics.
A paper by Bell that goes into this point more clearly than I can articulate: http://www.tau.ac.il/~vaidman/IQM/BellAM.pdf
Sure, modeling decoherence is not always easy. (And, 'collapse' is often a nice simplification for practical purposes.)
Now, this can be rectified by using many worlds, for example. Particularly, integrating out the wave function to get a mass density on 3-space (non-relativistic version) does produce a valid theory which has multiple realities whose evolutions internally would appear to have single outcomes even when that is not actually true. Fuzzy tv reception with multiple overlapping channels is the mental model here.
However, that is not just decoherence. One has to add something. And the question is, why choose a theory that denies the truth of our common experience in such a fundamental way when one does not need to do so?
Pilot-wave theory is, subjectively, very simple and natural. It is not epicycles upon epicycles. In fact, quantum theory practically screams out for it with the existence of the probability current and the many insights that that current drives. There are at least 5 very distinct ways to derive pilot-wave theory from quantum notions.
One last thing to ponder. Wave functions are defined on the configuration space of the particles. The specific space is crucial to defining the evolution operator. Fermions and bosons emerge naturally by considering the configuration space of unlabeled particles.
But if you have no particles, why is a configuration of them useful at all?
It probably isn't really progress in the sense the article writer thinks; juggling isomorphic representations is in some sense not "really" progress. But it can still be worth it for the practical improvements and potential didactic improvements. Perhaps if we had better education for QM with a better mathematical model, it would lead to less existential angst in the first place. I've seen Scott Aaronson trying to do some work on that front as well. In fact I'd consider it ironic if QM turns out merely to be slightly difficult and a hundred years of psuedo-philosophical babbling sourced from nothing more than a slanted view of relatively simple principles. I think some people will actually get upset if there is success in taking the mysticism away from QM....
Axioms of QM are few and clean. Sure, playing around them may be interesting. And if someone found its alternative formulation, more fundamental theory or anything - it would be great.
But (looking at the history of science) I see that the search of mathematical beauty sometimes leads to great discoveries; trying to satiate one's naive intuitions - rarely.
As someone who is bad at math and physics, the complaints don't seem all that different than first-year students scoffing at imaginary numbers, or centrifugal force. You don't "get it" -- so what? Why should the universe be easy to understand? QM just seems like more of the same.
People could handle heliocentricity, then the galaxy, then the universe, but for whatever reason, QM is just a bridge too far. Too weird, I guess.
It looks familiar actually; it could be posted on HN or had generated an initial pop science hype wave when it was first published.
Back then Egyptians were sure that everything they do makes a perfect sense - the height and shape of structures are in accordance with the opinion of the most knowledgable and authoritative experts, writings on the walls are perfectly correct and verified many times, etc.
Beaides which, the pyramids are pretty remarkable from a scientific and mathematical standpoint.
When I look at the (often) over engineered (by modern standards) Victorian bridges and such I don't scoff because they didn't understand the tensile strength of the materials like we do now I appreciate the mastery they had at the time.
There is still no consensus among philosophers and, of course, no empirical evidence of existence of time as a phenomena of the Universe, apart from mental concept which could be derived from this or that physical processes using mathematical modeling. But for math models being proven does not imply existence. There are phenomena we call "mass", and hence phenomena we call forces, there is notion of distance, succession, rate of change, but there is no phenomena of time apart from some physical process observable by a mind. The famous clocks being accelerated is mere a mental construct.
How come that we are so convinced that time exist? Well, suppose you have arrived to some big Tibetan Monastery in Lhasa or Shigatse at the beginning of the last century. You will be overwhelmed by the architecture, paintings, buzzing activities, which all seemingly makes perfect sense for those who performs them. All the rituals, offerings, recitation of scriptures, daily duties, strict hierarchy, etc. Much like MIT nowadays.)
Unless you are questioning everything, trying to reduce everything back to first principles, being skeptical and aware of socially constructed dogmas, you will be convinced very quickly that there are various buddhas and other deities which appear and disappear upon their will, that they hide some scriptures in the past, to be revealed when humanity will be ready for the knowledge. You will study cosmology, reasoning, philosophy of emptiness, as a refinement of crude ancient Indian philosophy (which is the only real marvel Tibetan culture produced) and so on. If you are good student you will become very good rimpoche, expert in all the subtle details of the teachings. I am seasonal guide in Tibet, so I know what I am talking about.)
What do we call notions held firmly by society but which cannot be empirically proven? We call it beliefs. How do we call organized beliefs, supported by social institutions? We call it a religion. Modern quantum physics is nothing but a bunch of religious sects.
BTW, traditional Indian philosophy, which goes back to Upanishads, put the human mind in the center, so it could observe itself, how easily and readily it produces chimeras and dogmas. The two almost unbreakable of these is "myself" and "time". Upanishads were the very first systematic discourses which attempted to prove logically non-existence of these mental concepts. Still, no one managed to refute Upanishads. "A priori" established by Kant is related to that mind - an observer, not to the observed Universe.
Newtonian / Classical Mechanics is an effective theory in the technical sense[0], which means that it is independent (up to some unspecified constants) of the finer underlying details.
Yes, we may be wrong about how we see the world. But wrong is relative. No amount of science or new discovery will make us see the Earth as flat. [1]
[0] https://en.wikipedia.org/wiki/Effective_theory
[1] http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htmWell, you list "rate of change" among your phenomena, but deny time as part of the phenomena. But how can rate of change be a "real" phenomena without time also being "real" in the same sense? "Rate of change" is really "rate of change with respect to time", after all.
I won't bore you with an exegesis of how accurate the current Standard Model is when it comes to making predictions about lepton and hadron behavior. I'll simply emphasize that the behavior it's good for won't change tomorrow even if all our opinions change. That means any new theory will have to make all the same predictions about all the same behavior, just like Special Relativity has to agree with Newtonian mechanics in the low-speed realm.
I'll close with an apposite link: "The Relativity of Wrong" by Asimov
http://chem.tufts.edu/answersinscience/relativityofwrong.htm
> [W]hen people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together.
What? So much for purifying the discussion. I know a little about the history of electronics and do not remember any discussion of quantum mechanics by those building the first computers, lasers or transistors. These were rather practical inventions based on easily observable experimentation.
The field of quantum physics certainly allows us to better understand how and why these devices work, and to improve them, but it is not responsible for their existence.
Computers are constructed with semiconductors.
I use and write atomistic simulators and semi-classical (finite-element analysis based) simulators to simulate modern FET devices every day as part of my research. I literally use quantum mechanics to write the algorithms behind the simulator (DFT, NEGF in my case). Moreover, if you look at the manual for Synopsys Sentaurus (which is the semi-classical simulator), they have hundreds of pages describing the derivation of their mobility models and structural models from basic quantum theory.
In summary, modern transistors are most definitely constructed taking quantum mechanics into account because without it you wouldn't have transistors functioning at 90nm much less at 14nm. You wouldn't take into account gate-leakage, tunneling, stress, bandstructures, and a host of other properties of modern transistors.