# A neat experiment concerning quantum jumps. Also, an update on the data science side.

1. A new paper on quantum jumps:

This post has a reference to a paper published yesterday in Nature by Z. K. Minev and pals [^]; h/t Ash Joglekar’s twitter feed (he finds this paper “fascinating”). The abstract follows; the emphasis in bold is mine.

In quantum physics, measurements can fundamentally yield discrete and random results. Emblematic of this feature is Bohr’s 1913 proposal of quantum jumps between two discrete energy levels of an atom[1]. Experimentally, quantum jumps were first observed in an atomic ion driven by a weak deterministic force while under strong continuous energy measurement[2,3,4]. The times at which the discontinuous jump transitions occur are reputed to be fundamentally unpredictable. Despite the non-deterministic character of quantum physics, is it possible to know if a quantum jump is about to occur? Here we answer this question affirmatively: we experimentally demonstrate that the jump from the ground state to an excited state of a superconducting artificial three-level atom can be tracked as it follows a predictable ‘flight’, by monitoring the population of an auxiliary energy level coupled to the ground state. The experimental results demonstrate that the evolution of each completed jump is continuous, coherent and deterministic. We exploit these features, using real-time monitoring and feedback, to catch and reverse quantum jumps mid-flight—thus deterministically preventing their completion. Our findings, which agree with theoretical predictions essentially without adjustable parameters, support the modern quantum trajectory theory[5,6,7,8,9] and should provide new ground for the exploration of real-time intervention techniques in the control of quantum systems, such as the early detection of error syndromes in quantum error correction.

Since the paper was behind the paywall, I quickly did a bit of googling and then (very) rapidly browsed through the following three: [^], [^] and [(PDF) ^].

Since I didn’t find the words “modern quantum trajectory theory” explained in simple enough terms in these references, I did some further googling on “quantum trajectory theory”, high-speed browsed through them a bit, in the process browsing jumping through [^], [^], and landed first at [^], then at the BKS paper [(PDF) ^]. Then, after further googling on “H. J. Carmichael”, I high-speed browsed through the Wiki on Prof. Carmichael [^], and from there, through the abstract of his paper [^], and finally took the link to [^] and to [^].

My initial and rapid judgment:

Ummm… Minev and pals might have concluded that their experimental work lends “support” to “the modern quantum trajectory theory” [MQTT for short.] However, unfortunately, MQTT itself is not sufficiently deep a theory.

…  As an important aside, despite the word “trajectory,” thankfully, MQTT is, as far as I gather it, not Bohmian in nature either. [Lets out a sigh of relief!]

Still, neither is MQTT deep enough. And quite naturally so… After all, MQTT is a theory that focuses only on the optical phenomena. However, IMO, a proper quantum mechanical ontology would have the photon as a derived object—i.e., a higher-level abstraction of an object. This is precisely the position I adopted in my Outline document as well [^].

Realize, there  can be no light in an isolated system if there are no atoms in it. Light is always emitted from, and absorbed in, some or the other atoms—by phenomena that are centered around nuclei, basically. However, there can always be atoms in an isolated system even if there never occurs any light in it—e.g., in an extremely rare gas of inert gas atoms, each of which is in the ground state (kept in an isolated system, to repeat).

Naturally, photons are the derived or higher-level objects. And that’s why, any optical theory would have to assume some theory of electrons lying at even deeper a level. That’s the reason why MQTT cannot be at the deepest level.

So, my overall judgment is that, yes, Minev and pals’ work is interesting. Most important, they don’t take Bohr’s quantum jumps as being in principle un-analyzable, and this part is absolutely delightful. Still, if you ask me, for the reasons given above, this work also does not deal with the quantum mechanical reality at its deepest possible level. …

So, in that sense, it’s not as fascinating as it sounds on the first reading. … Sorry, Ash, but that’s how the things are here!

…Today was the first time in a couple of weeks or so that I read anything regarding QM. And, after this brief rendezvous with it in this post, I am once again choosing to close that subject right here. … In the absence of people interacting with me on QM (computational QChem, really speaking), and having already reached a very definite point of development concerning my new approach, I don’t find QM to be all that interesting these days.

Addendum on 2019.06.06:

For some good pop. sci-level coverage of the paper, see Chris Lee’s post at his ArsTechnica blog [^], and Phillip Ball’s story at the Quanta Magazine [^].

2. An update on the Data Science side:

As you know, these days, I have been pursuing data science full-time.

Earlier, in the second half of 2018, I had gone through Michael Nielsen’s online book on ANNs and DL [^]. At that time, I had also posted a few entries here on this blog concerning ANNs and DL [^]. For instance, see my post explaining, with real-time visualization, why deep learning is hard [^].

Now, in the more recent times, I have been focusing more on the other (“canonical”) machine learning techniques in general—things like (to list in a more or less random an order) regression, classification, clustering, dimensionality reduction, etc. It’s been fun. In particular, I have come to love scikit-learn. It’s a neat library. More about it all, later—may be I should post some of the toy Python scripts which I tried.

… BTW, I am also searching for one or two good, “industrial scale” projects from data science. So, if you are from industry and are looking for some data-science related help, then feel free to get in touch. If the project is of the right kind, I may even work on it on a pro-bono basis.

… Yes, the fact is that I am actively looking out for a job in data science. (Have uploaded my resume at naukri.com too.) However, at the same time, if a topic is interesting enough, I don’t mind lending some help on a pro bono basis either.

The project topic could be anything from applications in manufacturing engineering (e.g. NDT techniques like radiography, ultrasonics, eddy current, etc.) to financial time-series predictions, to some recommendation problem, to… I am open for virtually anything in data science. It’s just that I have to find the project to be interesting enough, that’s all… So, feel free to get in touch.

… Anyway, it’s time to wrap up. … So, take care and bye for now.

A song I like

(Western, pop) “Money, money, money…”
Band: ABBA

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# An update on my research

28th February is the National Science Day in India.

The story goes that it was on this day (in 1928) that C. V. Raman discovered the effect known by his name.

I don’t believe that great discoveries like that are made in just one single day. There is a whole sequence of many crucially important days involved in them.

Yes, on this day, Raman might have achieved a certain milestone or made a key finding regarding his discovery. However, even if true in this case (which I very much doubt), it’s not true in general. Great discoveries are not made in a single day; they are usually spread over much longer span of time. A particular instant or a day has more of just a symbolic value—no matter how sudden the discovery might have looked to someone, including to the discoverer.

There of course was a distinguished moment when Kekule, in his famous dream, saw a snake swallowing its own tail. However, therefore to say that he made the discovery concerning the ring structure of the benzene molecule, just in a single moment, or in a single flash of imagination, is quite a bit of a stretch.

Try it out yourself. Think of a one-line statement that encapsulates the findings of a discovery made by a single man. Compare it with another statement which encapsulates any of the previous views regarding the same matter (i.e., before this discovery came along). This way, you can isolate the contributions of a single individual. Then analyze those contributions. You would invariably find that there are several different bits of progress that the discovery connected together, and these bits themselves (i.e., the contributions made individually by the discoverer himself) were not all discovered on the same day. Even if a day or an hour is truly distinctive in terms of the extent of progress made, it invariably has the character of taking an already ongoing process to a state of completion—but not of conducting that entire process. Mystical revelation is never a good metaphor to employ in any context—not even in the spiritual matters, let alone in the scientific ones.

Anyway, it’s nice that they didn’t choose Raman’s birth-day for this Day, but instead chose a day that was related to his most famous work in science. Good sense! And easy to remember too: 28-02-’28.

Let me celebrate this year’s Science Day in my own, small, personal way. Let me note down a bit of an update on my research.

1. I have had a bit of a correspondence, regarding my new approach, with a couple of physicists. Several objections were made by them, but to cut a long story short, neither seemed to know how to get into that mode kind of thinking which most naturally leads to my main thesis, and hence helps understand it.

The typical thought process both these physicists displayed was the one which is required in finding analytical solutions of problems of a certain kind, using an analysis of a specific kind. But it is not the kind of thought process which is typically required in the computational modeling of complex phenomena. Let me remind you that my theory is nonlinear in nature. Nonlinearity, in particular, is best approached only computationally—you would be hopelessly out of your wits if you try to find analytical solutions to a nonlinear system. What you should instead pursue is: thinking in terms of the following ingredients: certain objects, an algorithm to manipulate their states, and tracing the run-time evolution of the system. You try this algorithmic way of thinking, and the whole thing (I mean understanding the nature of a nonlinear system) becomes easy. Otherwise, it looks hopelessly complicated, incomprehensible, and therefore, deeply suspicious, if not outright wrong. Both the physicists with who I interacted seemed to be thinking in terms of the linear theory of QM, thereby restricting their thought modes to only the traditional formalism based on the abstract Hilbert-spaces and linear Hermitian operators. Uh oh! Not good. QM is fundamentally nonlinear; the linear formulations of QM are merely approximations to its true nature. No matter how analytically rigorous you can get in the traditional QM, it’s not going to help you understand the true nature of quantum phenomena, simply because a linear system is incapable of throwing much light on the nonlinear system of which it is an approximation.

I believe it was out of this reason—their continuing to think in terms of linear systems defined over hyperspaces and the operator algebra—that one of them raised the objection that if $\Psi$ in MSQM (mainstream QM) is defined on a $3ND$ configuration space, how come my $\Psi(x,t)$ could be defined over the physical $3D$ space. He didn’t realize, even after I supplied the example of the classical $N$-particle molecular dynamics (MD) simulations, that using an abstract higher-dimensional space isn’t the only viable manner in which you can capture the physics of a situation. (And I had indicated right in the Outline document too, that you first try to understand how a Newtonian evolution would work for multiple, charged, point-particles as in classical physics, and only then modify this evolution by introducing the system wavefunction.)

I came to gather that apparently, some people (who follow the Bohmian mechanics doctrine) have tried to find a $3ND \leftrightarrow 3D$ correspondence for a decade, if not more. Apparently, they didn’t succeed. I wonder why, because doing so should be so damn straight-forward (even if it would not be easy). You only have to realize that a configuration space refers to all possible configurations, whereas what an evolution over a $3D$ physical space directly deals with is only one initial configuration at a time. That is what specifying the ICs and the BCs does for you.

In case of MD simulations, you don’t define a function over the entire $3ND$ configuration space in the first place. You don’t try to produce an evolution equation which relies on only those kinds of operators which modify all parts of the entire hyperspace-function in one shot, simultaneously. Since you don’t think in such hyperspace terms in the first place, you also don’t have to think in terms of the projection operators bringing the system dynamics down to $3D$ in particular cases either. You don’t do that in the context of MD simulations, and you don’t do it in the context of my approach either.

This physicist also didn’t want me to say something using analogies and metaphors, and so I didn’t mention it to him, but I guess I can use an analogy here. It will allow even a layman to get a sense of the issue right.

This physicist was insisting on having a map of an entire territory, and was more or less completely dismissing my approach on the grounds that I only supply the surveying instruments like the theodolite and the triangulation algorithm. He expected to see the map—even when a theory is at a fledgling stage. He nevertheless was confident that I was wrong because I was insisting that each physical object in the actual territory is only at one place at any given instant, that it is not spread all over the map. This analogy is not exact, but it is helpful: it does bring out the difference of focusing on only the actually followed trajectory in the configuration space, vs. an insistence on using the entirety of the configuration space for any description of an evolution. But that guy didn’t get this point either. And he wanted equations, not analogies or metaphors.

Little wonder they have not been successful in finding out what logical connection there is between the abstract $3ND$ hyperspace on the one hand, and the $3D$ physical space on the other hand. Little wonder they don’t progress despite having worked on the problem for a decade or so (as this guy himself said).

Yeah, physicists, work harder, I say! [LOL!]

2. Apart from it all—I mean all those “discussions”—I have also realized that there are several errors or confusing explanations in the Outline document which I uploaded at iMechanica on 11th February 2019. Of course, these errors are more minor in nature. There are many, many really important ideas in that document which are not in error.

The crucially important and new ideas which are valid include, just to cite a few aspects: (i) my insistence on using only those potentials that are singularly anchored into the point-particle charges, (ii) the particular nonlinearity I have proposed for the system evolution, (iii) the idea that during a measurement it is the Instrument whose state undergoes a cascade of bifurcations or catastrophic changes, whereas the System state essentially remains the same (that there is no wavefunction collapse). And, many, many other ideas too. These ideas are not only crucial to my approach but they also are absolutely new and original. (Yes, you can be confident about this part, too—else, Americans would have pointed out the existing precedence by now. (They are just looking to find errors in what(ever) I say.)) All these ideas do remain intact. The confusing part or the one having erroneous statements indeed is more minor. It concerns more with how I tried to explain things. And I am working on removing these errors too.

I have also come to realize that I need to explicitly give a set of governing equations, as well as describe the algorithm that could be used in building the simulations. Yes, the physicist had asked me for an evolution equation. I thought that any one, given the Schrodinger equation and my further verbal additions / modifications to it, could easily “get” it. But apparently, he could not. So, yes, I will explicitly write down the evolution equation for my approach, as an equation that is separate from Schrodinger’s. In the next revision of the document (or addition to it) I will not rely on the only implicitly understood constraints or modifications to the TDSE.

3. There also are some other issues which I noticed entirely on my own, and I am working on them.

One such issue concerns the way the kinetic energy is captured in the MSQM vs. how my approach ought to handle and capture it.

In MSQM, the kinetic energy consists of a sum of 1-particle Laplacian operators that refer to particle coordinates. Given the fact that my approach has the wavefunction defined over the $3D$ space, how should this aspect be handled? … By the time I wrote my Outline document (version 11 February 2019), I had not thought a lot about the kinetic energy part. Now, I found out, I have to think really deep about it. May be, I will have to abandon the form of Schrodinger’s equation itself to a further extent. Of course, the energy analysis will progress on the same lines (total energy = kinetic + potential), and the de Broglie relations will have to be honored. But the form of the equation may turn out to be a bit different.

You see, what MSQM does is to represent the particles using only the $\Psi(x,t)$ field. The potential energy sure can be constructed in reference to a set of discrete particle positions even in MSQM, but what the $\hat{V}$ operator then yields is just a single number. (In case of time-dependent potentials, the value of this variable varies in time.) The multiplication by the hyperspace-function $\Psi(x,t)$ then serves to distribute this much amount of energy (that single number) over the entire hyperspace. Now realize that $|\Psi(x,t)|^2$ gives the probability. So, in a way, indirectly, even if you can calculate / compute the potential energy of the system starting from a certain set of particle positions, in the MSQM, you then have to immediately abandon them—the idea of the discrete particles. The MSQM formalism doesn’t need it—the particle positions. You deal only with the hyperspace-occupying $\Psi(x,t)$. The formulation of kinetic energy also refers to only the $\Psi(x,t)$ field. Thus, in MSQM, particles are ultimately represented only via the $\Psi(x,t)$ field. The $\Psi(x,t)$ is the particles.

In contrast, in my approach, the particles are represented directly as point-phenomena, and their positions remain significant throughout. The $\Psi(x,t)$ field of my approach connects, and causally interacts with, the particles. But it does not represent the particles. Ontologically, $\Psi(x,t)$ is basically different from particles, even if the background object does interacts with the particles. Naturally, why should I represent their kinetic energies via the Laplacian terms? … Got the idea? The single number that is the kinetic energy of the particles, need not be regarded as being distributed over the $3D$ space at all, in my approach. But in 11th February version of the Outline document, I did say that the governing equation is only Schrodinger’s. The modifications required to be made to the TDSE on account of the kinetic energy term, is something I had not even thought of, because in writing that version, I was trying focusing on getting as many details regarding the potential energy out as possible. After all, the nonlinear nature of QM occurs due to the potential term, doesn’t it?

So, I need to get issues like these straightened out too.

… All in all, I guess I can say that I am more or less (but not completely) done with the development concerning the spin-less 1-particle systems, esp. the time-independent states. So far, it seems that my approach does work fine with them. Of course, new issues continue to strike me all the time, and I continue finding answers to them as well—as happens in any approach that is completely new. New, right from the stage of the very basic ideation  concerning what kind of objects there should be, in the theory.

I have just about begun looking into the (spin-less) multi-particle states. That is the natural order in which the theory should progress, and my work is tracing just this same path. But as I said, I might also be revising some parts of the earlier presented theory, as and when necessary.

4. I also realized on my own, but only after the interaction with the physicists was already over, that actually, I need not wait for the entire multi-particle theory to get developed before beginning with simulations. In fact, it should be possible to handle some simple 1-particle $1D$ cases like the particle in a box or the QHO (quantum-mechanical oscillator) right away.

I plan to pursue these simulations right in the near future. However, I will not be able to complete pursuing all their aspects in the near future—not even in the simple cases involving just $1D$ simulations. I plan to do a preliminary simulation or two, and then suspend this activity until the time that I land a well-paying job in data science in Pune.

No songs section this time because I happened to post several entries almost back to back here, and in the process, I seem to have used up all the songs that were both new (not run here before) and also on the top of my mind. … May be I will return later and add a song if one strikes me easily.

Bye for now, and have a happy Science Day!

Minor editing may be done later today. Done by 20:15 hrs the same day.

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# The bouncing droplets imply having to drop the Bohmian approach?

If you are interested in the area of QM foundations, then may be you should drop everything at once, and go, check out the latest pop-sci news report: “Famous experiment dooms alternative to quantum weirdness” by Natalie Wolchover in the Quanta Magazine [^].

Remember the bouncing droplets experiments performed by Yves Couder and pals? In 2006, they had reported that they could get the famous interference pattern even if the bouncing droplets passed through the double slit arrangement only one at a time. … As the Quanta article now reports, it turns out that when other groups in the USA and France tried to reproduce this result (the single-particle double-slit interference), they could not.

“Repeat runs of the experiment, called the “double-slit experiment,” have contradicted Couder’s initial results and revealed the double-slit experiment to be the breaking point of both the bouncing-droplet analogy and de Broglie’s pilot-wave vision of quantum mechanics.”

Well, just an experimental failure or two in reproducing the interference, by itself, wouldn’t make for a “breaking point,”i.e., if the basic idea itself were to be sound. So the question now becomes whether the basic idea itself is sound enough or not.

Turns out that a new argument has been put forth, in the form of a thought experiment, which reportedly shows why and how the very basic idea itself must be regarded as faulty. This thought experiment has been proposed by a Danish professor of fluid dynamics, Prof. Tomas Bohr. (Yes, there is a relation: Prof. Tomas Bohr is a son of the Nobel laureate Aage Bohr, i.e., a grandson of the Nobel laureate Niels Bohr [^].)

Though related to QM foundations, this thought experiment is not very “philosophical” in nature; on the contrary, it is very, very “physics-like.” And the idea behind it also is “simple.” … It’s one of those ideas which make you exclaim “why didn’t I think of it before?”—at least the first time you run into it. Here is an excerpt (which actually is the caption for an immediately understandable diagram):

“Tomas Bohr’s variation on the famous double-slit experiment considers what would happen if a particle must go to one side or the other of a central dividing wall before passing through one of the slits. Quantum mechanics predicts that the wall will have no effect on the resulting double-slit interference pattern. Pilot-wave theory, however, predicts that the wall will prevent interference from happening.”

… Ummm… Not quite.

From whatever little I know about the pilot-wave theory, I think that the wall wouldn’t prevent the interference from occurring, even if you use this theory. … It all seems to depend on how you interpret (and/or extend) the pilot-wave theory. But if applied right (which means: in its own spirit), then I guess that the theory is just going to reproduce whatever it is that the mainstream QM predicts. Given this conclusion I have drawn about this approach, I did think that the above-quoted portion was a bit misleading.

The main text of the article then proceeds to more accurately point out the actual problem (i.e., the way Prof. Tomas Bohr apparently sees it):

“… the dividing-wall thought experiment highlights, in starkly simple form, the inherent problem with de Broglie’s idea. In a quantum reality driven by local interactions between a particle and a pilot wave, you lose the necessary symmetry to produce double-slit interference and other nonlocal quantum phenomena. An ethereal, nonlocal wave function is needed that can travel unimpeded on both sides of any wall. [snip] But with pilot waves, “since one of these sides in the experiment carries a particle and one doesn’t, you’ll never get that right. You’re breaking this very important symmetry in quantum mechanics.””

But isn’t the pilot wave precisely ethereal and nonlocal in nature, undergoing instantaneous changes to itself at all points of space? Doesn’t the pilot theory posit that this wave doesn’t consist of anything material that does the waving but is just a wave, all by itself?

…So, if you think it through, people seem to be mixing up two separate issues here:

1. One issue is whether it will at all be possible for any real physical experiment done up with the bouncing droplets to be able to reproduce the predictions of QM or not.
2. An entirely different issue is whether, in Bohr’s dividing-wall thought-experiment, the de Broglie-Bohm approach actually predicts something that is at a variance from what QM predicts or not.

These two indeed are separate issues, and I think that the critics are right on the first count, but not necessarily on the second.

Just to clarify: The interference pattern as predicted by the mainstream QM itself would undergo a change, a minor but a very definite change, once you introduce the middle dividing wall; it would be different from the pattern obtained for the “plain-vanilla” version of the interference chamber. And if what I understand about the Bohmian mechanics is correct, then it too would proceed to  produce exactly the same patterns in both these cases.

With that said, I would still like to remind you that my own understanding of the pilot-wave theory is only minimal, mostly at the level of browsing of the Wiki and a few home pages, and going through a few pop-sci level explanations by a few Bohmians. I have never actually sat down to actually go through even one paper on it fully (let alone systematically study an entire book or a whole series of articles on this topic).

For this reason, I would rather leave it to the “real” Bohmians to respond to this fresh argument by Prof. Tomas Bohr.

But yes, a new argument—or at least, an old argument but in a remarkably new settings—it sure seems to be.

How would the Bohmians respond?

If you ask me, from whatever I have gathered about the Bohmians and their approach, I think that they are simply going to be nonchalant about this new objection, too. I don’t think that you could possibly hope to pin them down with this argument either. They are simply going to bounce back, just like those drops. And the reason for that, in turn, is what I mentioned already here in this post: their pilot-wave is both ethereal and nonlocal in the first place.

So, yes, even if Wolchover’s report does seem to be misguided a bit, I still liked it, mainly because it was informative on both the sides: experimental as well as theoretical (viz., as related to the new thought-experiment).

In conclusion, even if the famous experiment does not doom this (Bohmian) alternative to the quantum weirdness, the basic reason for its unsinkability is this:

The Bohmian mechanics is just as weird as the mainstream QM is—even if the Bohmians habitually and routinely tell you otherwise.

When a Bohmian tells you that his theory is “sensible”/“realistic”/etc/, what he is talking about is: the nature of his original ambition—but not the actual nature of his actual theory.

To write anything further about QM is to begin dropping hints to my new approach. So let me stop right here.

[But yes, I am fully ready willing from my side to disclose all details about it at any time to a suitable audience. … Let physics professors in India respond to my requests to let me conduct an informal (but officially acknowledged) seminar on my new approach, and see if I get ready to deliver it right within a week’s time, or not!

[Keep waiting!]]

Regarding other things, as you know, the machine I am using right now is (very) slow. Even then, I have managed to run a couple of 10-line Python scripts, using VSCode.

I have immediately taken to liking this IDE “code-editor.” (Never had tried it before.) I like it a lot. … Just how much?

I think I can safely say that VSCode is the best thing to have happened to the programming world since VC++ 6 about two decades ago.

Yes, I have already stopped using PyCharm (which, IMHO, is now the second-best alternative, not the best).

No songs section this time, because I have already run a neat and beautiful song just yesterday. (Check out my previous post.) … OK, if some song strikes me in a day or two, I will return here to add it. Else, wait until the next time around. … Until then, take care and bye for now…

[Originally published on 16 October 2018 22:09 hrs IST. Minor editing (including to the title line) done by 17 October 2018 08:09 hrs IST.]

# The quantum mechanical features of my laptop…

My laptop has developed certain quantum mechanical features after its recent repairs [^]. In particular, if I press the “power on” button, it does not always get “measured” into the “power-on” state.

That’s right. In starting the machine, it is not possible to predict when the power-on button may work, when it may lead to an actual boot-up. Sometimes it does, sometimes it doesn’t.

For instance, the last time I shut it down was on the last night, just before dinner. Then, after dinner, when I tried to restart it, the quantum mechanical features kicked in and the associated randomness was such that it simply refused the request. Ditto, this morning. Ditto, early afternoon today. But now (at around 18:00 hrs on 09 October), it somehow got up and going!

Fortunately, I have taken backup of crucial data (though not all). So, I can afford to look at it with a sense of humour.

But still, if I don’t come back for a somewhat longer period of time than is usual (about 8–10 days), then know that, in all probability, I was just waiting helplessly in getting this thing repaired, once again. (I plan to take it to the repairsman tomorrow morning.) …

…The real bad part isn’t this forced break in browsing or blogging. The real bad part is: my inability to continue with my ANN studies. It’s not possible to maintain any tempo in studies in this now-on-now-off sort of a manner—i.e., when the latter is not chosen by you.

Yes, I do like browsing, but once I get into the mood of studying a new topic (and, BTW, just reading through pop-sci articles does not count as studies) and especially if the studies also involve programming, then having these forced breaks is really bad. …

Anyway, bye for now, and take care.

PS: I added that note on browsing and then it struck me. Check out a few resources while I am gone and following up with the laptop repairs (and no links because right while writing this postscript, the machine crashed, and so I am somehow completing it using smartphone—I hate this stuff, I mean typing using at most two fingers, modtly just one):

1. As to Frauchiger and Renner’s controversial much-discussed result, Chris Lee’s account at ArsTechnica is the simplest to follow. Go through it before any other sources/commentaries, whether to the version published recently in Nature Comm. or the earlier ones, since 2016.
2. Carver Mead’s interview in the American Spectator makes for an interesting read even after almost two decades.
3. Vinod Khosla’s prediction in 2017 that AI will make radiologists obsolete in 5 years’ time. One year is down already. And that way, the first time he made remarks to that sort of an effect were some 6+ years ago, in 2012!
4. As to AI’s actual status today, see the Quanta Magazine article: “Machine learning confronts the elephant in the room” by Kevin Hartnett. Both funny and illuminating (esp. if you have some idea about how ML works).
5. And, finally, a pretty interesting coverage of something about which I didn’t have any idea beforehand whatsoever: “New AI strategy mimics how brains learn to smell” by Jordana Cepelwicz in Quanta Mag.

Ok. Bye, really, for now. See you after the laptop begins working.

A Song I Like:
Indian, instrumental: Theme song of “Malgudi Days”
Music: L. Vaidyanathan

# NASA’s EM drive, and the nature of the quantum theory

NASA’s EM drive has made it to the Forbes. Brian Koberlein, an astrophysicist who teaches at the Rochester Institute of Technology, provides a decent coverage; see, here [^].

First things first. I hardly know anything about the EM drive. Yes, I did go through the news reports about it a week ago or so, but about the only salient thing I noticed was that it was a replication of a result. The original result itself was found by the physicists community to be, to make an understatement, something like absolutely enormously incredible. … Given NASA’s reputation (at least among the physicists community), therefore, the scene would be ripe for quite some energetic speculations—at least discussions. Newsworthy.

But still, I myself don’t know much about the experiment. Not even a schematic sketch of the apparatus was provided in the general news coverage about the experiment so far, and I didn’t look into the paper itself because I knew it would be beyond me.

But since it was the Forbes where Koberlein’s coverage appeared, I decided to go through it. The description would be dumbed down enough that even I could get something out of it, I thought.

Well, even in this Forbes piece, there was no discussion of the actual apparatus, but the author did discuss the issue in terms of the Copenhagen interpretation, and that’s where the story became interesting to me. Koberlein writes:

In the usual Copenhagen interpretation of quantum theory, an object is defined by its wavefunction. The wavefunction describes the probability of finding a particle in a particular location. The object is in an indefinite, probabilistic state described by the wavefunction until it is observed. When it is observed, the wavefunction collapses, and the object becomes a definite particle with a definite location.

I am not an expert on the Copenhagen interpretation. However, I can tell that most popular science books would present the Copenhagen interpretation exactly in this manner. So, you can’t say that the author was presenting the Copenhagen interpretation in a misleading way. (Why, I even remember John Gribbin (Schrodinger’s Cat, and later, … Kitten), and Alastair Rae (Illusion or Reality) presenting these matters more or less precisely this way about a quarter of a century ago, if not earlier.)

Still, I did have an issue here. It is in the very last sentence in the quoted passage.

As you know, I have been writing and re-writing, and arranging and re-arranging the “syllabus” for my planned “book” on QM. In particular, these past few days, I have been doing exactly that. Since the subject matter thus was fresh in my mind, I could see that the way that the QM was developed by the original masters (Heisenberg, Schrodinger, Pauli, …), the spirit of their actual theorization was such that the last sentence in the quoted passage could not actually be justified.

Even though the usual mainstream QM presentation proceeds precisely along those lines, the actual spirit of the theorization by the original founders, has begun looking different to me.

I have a very difficult position to state here, so let me try to put it using some other words:

I am not saying that Koberlein’s last sentence is not a part of the Copenhagen interpretation. I am also not saying that Heisenberg did not have the Copenhagen interpretation in his mind, whenever he spoke about QM (as in contrast to discovering and working on QM). I am also aware that Schrodinger wanted to get rid of the quantum jumps—and could find no way to do so.

Yet, what I am saying is this: Given my self-study of QM using university text-books (like McQuarry, Resnick, Griffiths, Gasiorowicz, …), esp. over the last year, I can now clearly see that the collapse postulate wasn’t—or shouldn’t have been—a part of the spirit of the original theory-building.

Since I am dwelling on the spirit of the original (non-relativistic) QM, it is relevant to point out to you to someone who has putting up a particularly spirited defence of it over a period of time. I mean the Czeck physicist Lubos Motl. See, for example his post: “Stupidity of the pop science consensus about `many worlds’ ”  [^]. Do go through it. Highly recommended. I know that Motl often is found involved in controversies. However, in this particular post (and the related and similar posts he has been making for quite some time), he remains fairly well-focused on the QM itself. He also happens to be extraordinarily lucid and clear in this post; see his discussion of the logical OR vs. the logical AND, for instance.

Even though Motl seems to have been arguing for the original founders, if you think through his writings, it also seems as if he does not place too much of an emphasis on the collapse postulate either—even though they did. He in fact seems to think that QM needs no interpretation at all, and as I suppose, this position would mean that QM does not need the Copenhagen interpretation (complete with the collapse postulate) either.

No, considering all his relevant posts about QM over time, I don’t think that I can agree with Motl; my position is that QM is incomplete, whereas he has strongly argued that it is complete. (I will come to show you how QM is incomplete, but first, I have to complete writing the necessary pre-requisites in the form of my book). Yet, I have found his writings (esp. those from 2015-end) quite helpful.

The detour to Motl’s blog was not so much of a detour at all. Here is another post by Motl, “Droplets and pilot waves vs. quantum mechanics” [^], done in 2014. This post apparently was in response to Prof. Bush (MIT) et al’s droplets experiment, and Koberlein, in his Forbes story today, does touch upon the droplets experiment and the Bohm interpretation, even if only in the passing. As to me, well, I have written about both the droplets experiment as well as Bohm’s theory in the past, so let me not go there once again. [I will add links to my past posts here, in the revision tomorrow.] As a matter of fact, I sometimes wonder whether it wouldn’t be a good idea to stop commenting on QM until my book is in at least version 0.5.

Anyway, coming back to Koberlein’s piece, I really liked the way he contrasts Bohm’s theory from Copenhagen interpretation:

The pilot wave model handles quantum indeterminacy a different way. Rather than a single wavefunction, quanta consist of a particle that is guided by a corresponding wave (the pilot wave). Since the position of the particle is determined by the pilot wave, it can exhibit the wavelike behavior we see experimentally. In pilot wave theory, objects are definite, but nonlocal. Since the pilot wave model gives the same predictions as the Copenhagen approach, you might think it’s just a matter of personal preference. Either maintain locality at the cost of definiteness, or keep things definite by allowing nonlocality. But there’s a catch.

Although the two approaches seem the same, they have very different assumptions about the nature of reality.

No, Brian, they are the same—inasmuch as they both are essentially non-local, and give rise to exactly the same quantitative predictions. If so, it’s just us who don’t understand how their seemingly different assumptions mean the same underlying physics, that’s all.

That’s why, I will go out on a limb and say that if the new paper about NASA’s EM drive has successfully used the Bohmian mechanics, and if it does predict the experimental outcome correctly, then it’s nothing but some Bohmian faithfuls looking for a “killer app” for their interpretation, that’s all. If what I understand about QM is right, and if the Bohmian mechanics predicts something, it’s just a matter of time before the mainstream formalism of QM (roughly, the Copenhagen interpretation) would also begin to predict exactly the same thing. (In the past, I had made a statement in the reverse way: whether Bohmian mechanics is developed enough to give the same predictions as the mainstream QM, you can always expect that it would get developed soon enough.)

Anyway, interesting reading.

As to my own writings on QM (I mean presenting QM the way I would like to do), as I told you, I have been working on it in recent times, even if only in an off-and-on manner. Yet, by now, I am done through more than half of the phase of finalizing the “syllabus” topics and sequence. (Believe me, this was a major challenge. For a book on QM, deciding what thesis you have for your book, and finalizing the order in which the presentation should be made, is more difficult—far more difficult—than writing down the specific contents of the individual sections and the equations in them.)

Writing the book itself can start any time now, though by now I clearly know that it’s going to be a marathon project. Months, in the least, it will take for me to finish.

Also, don’t wait for me to put up parts of it on the Web, any time soon. … It is a fact that I don’t have any problem sharing my drafts before the publication of the book as such. Yet, it also is a fact that if every page is going to be changing every day, I am not going to share such premature “editions” publicly either. After all, sharing also means inviting comments, and if you yourself haven’t firmed up your writing, comments and all are likely to make it even more difficult to finish the task of writing.

But yes, after thinking off-and-on about it for years (may be 5+ years), and after undergoing at least two false starts (which are all gone in the HDD crashes I had), I am now happy about the shape that the contents are going to take.

More, may be later. As to the Song I Like section, I don’t have anything playing at the back of my mind right away, so let me see if something strikes me by the time I come back tomorrow to give a final editing touch to this post. In that case, I will add this section; else, not!

[E&OE]