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Quantum Mechanics for Programmers

kim.oyhus.no

21–30 of 79 posts

Re: Quantum Mechanics for Programmers

#21

> Since you are a programmer, you do not know what science is, even though you may believe you do. A hint: Computer science does not contain science, just mathematics. He probably wrote this half in jest, but it is actually a serious issue in fields like Natural Language Processing and Computer Vision that are have their intellectual roots in Computer Science. Papers in CV and NLP are about data structures, algorithm…

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Re: Quantum Mechanics for Programmers

#22

Hmm he seems to imply that MWI is the "right" interpretation, and that the measurement problem is solved. Most physicists would not agree. If you follow the link to his MWI description, there's this gem: > But fortunately, I knew computer science, which most physicists do not know, with the Church-Turing thesis, which roughly states that anything physical can be simulated by a computer. But that is not what the Churc…

I'm a quantum physicist (well, we don't say that, I'm an atomic physicist, but for anyone not aware it is 99% quantum mechanics we do all day), and the MWI isn't universally accepted, but it's not universally rejected either. Plenty of important physicists interpret quantum mechanics that way, and I do too (I am not important though). That's not to say I'm confident it's correct , just that it's the most sensible way…

I think that MWI is pretty much like any ontology, in that you find a lot more interest in it when you're not dealing with physicists. At the end of the day, it doesn't change the math, it doesn't change much of anything, and it probably isn't testable. For me, that has all of the hallmarks of an uninteresting topic.

Re: Quantum Mechanics for Programmers

#23

> Here is a model of waves, as in light or sound, but not as in water waves or electron waves How water waves are different from sound? Water wave are sound, aren't they?

The wave that he is modeling is due to having a field in space-time that will interact with nearby values of the same field in a linear way, which results in it moving at a constant rate.

The waves that you see in water are the surface representation of 3-d movements under the surface of the water. So you get effects such as the depth of the movement for a wave determines its velocity. A wave that moves a very deep water column moves very fast. (One that is a half-mile deep can move as fast as a jet!) A wave that moves a shallow water column moves slowly.

Another interesting fact about waves is that there is a significant nonlinear interaction between the depth of the water and the depth of the wave. As you come to shore this causes the wave to rise up. Surfers enjoy this effect when it comes to normal wind driven waves. But in the case of very deep and fast waves, the effect is very much like a tide unexpectedly coming in. The result is known as a tsunami or tidal wave.

These complex behaviors mean that water waves can behave very differently from light and sound.

Re: Quantum Mechanics for Programmers

#24

> Since you are a programmer, you do not know what science is, even though you may believe you do. A hint: Computer science does not contain science, just mathematics. He probably wrote this half in jest, but it is actually a serious issue in fields like Natural Language Processing and Computer Vision that are have their intellectual roots in Computer Science. Papers in CV and NLP are about data structures, algorithm…

I do research on Deep Learning. That seems the exact kind of question they would deem relevant to their field.

I don't know much about NLP but if I had to guess the answer to your question is include it in the training data. I don't know what model they use, but presumably it parses out sentence structure in a specific format and uses that as input to some neural network architecture.

Not really sure why he didn't answer your question, it's the exact kind of question people do NLP to answer.

Re: Quantum Mechanics for Programmers

#25

Earlier quoted context omitted.

I'm a quantum physicist (well, we don't say that, I'm an atomic physicist, but for anyone not aware it is 99% quantum mechanics we do all day), and the MWI isn't universally accepted, but it's not universally rejected either. Plenty of important physicists interpret quantum mechanics that way, and I do too (I am not important though). That's not to say I'm confident it's correct , just that it's the most sensible way…

> Furthermore, plenty of physicists don't actually grasp the fundamentals of their own field I once met a professor at a quantum chemistry conference who argued with me that I could not converge on the exact eigenvalues of a helium atom (assuming a simplified Hamiltonian with a few Coulombic terms). He stated the oft repeated mantra that "the Schrödinger equation can't be solved for any element other than hydrogen",…

> Another professor […] once said that the single particle wave function is more fundamental than the multi-particle wave function. Nevermind […] his research […] where the molecular wave function can't be well approximated using a product of single particle wave functions

Depends on what you mean by "multi-particle wave function". The way it is usually understood (I think), it includes all possible tensor products of single-particle wave functions. Then it should be possible, shouldn't it?

Re: Quantum Mechanics for Programmers

#26

The more I learn about physics and math, especially with regards to quantum theory, I start to get really freaked out. The amount of "neatness" to the universe is staggering. How there's no "inbetween" at the smallest scales. Everything is discrete. The fact that simple arrangements of symbols on a screen can perfectly describe this behavior is mind blowing. It leads me to think there's no possible way we're not livi…

> How there's no "inbetween" at the smallest scales. Everything is discrete.

I think the article is a bit misleading about this. We don't know if space and time are discrete or continuous. As far as we know space and time are continuous and all the current theories treat them as continuous values.

Discretization of space and time is useful for numerical simulations, if you pick the grid small enough, but it's only a trick to do the calculations in the computer.

Anyway, it is possible that someday in the future we will discover that space-time is discrete, and it has a really tiny grid, and it has a tiny effect in the calculations. But no one is sure if this will happen in the future or not.

Re: Quantum Mechanics for Programmers

#27

Hmm he seems to imply that MWI is the "right" interpretation, and that the measurement problem is solved. Most physicists would not agree. If you follow the link to his MWI description, there's this gem: > But fortunately, I knew computer science, which most physicists do not know, with the Church-Turing thesis, which roughly states that anything physical can be simulated by a computer. But that is not what the Churc…

I'm a quantum physicist (well, we don't say that, I'm an atomic physicist, but for anyone not aware it is 99% quantum mechanics we do all day), and the MWI isn't universally accepted, but it's not universally rejected either. Plenty of important physicists interpret quantum mechanics that way, and I do too (I am not important though). That's not to say I'm confident it's correct , just that it's the most sensible way…

> Furthermore, plenty of physicists don't actually grasp the fundamentals of their own field - they specialise a lot and can use specialised theories to get what they need done without understanding in detail where it came from.

This. Sometimes physics does feel like a religion. The fundamentals (including basic assumptions and "proofs" that are complete bs in the mathematical sense) are getting reiterated time and again till people actually start believing in them. From what I've experienced myself it basically works like this: In the beginning, you come across some claim or fundamental assumption you can't follow and make a mental note to follow up on it and sit down to fully understand it. Then you get sidetracked and next time you come across said claim, you're like "Damn, I wanted to look that up!" and here you are, making a mental note again… Now somewhere between the fifth and tenth time this happens, you've forgotten about your mental note completely and have just accepted the claim as fact.

It's basically the brain tricking you into thinking the claim is correct, the more often you read about it. It's like habitual behavior you don't actually process consciously anymore.

Re: Quantum Mechanics for Programmers

#28
I feel like this is what's wrong with the world: "In science one guesses at explanations. One does not deduce them like one do in math."

As a programmer who took quantum mechanics in college, I have to admit, I didn't understand most of it. Someone I respect once told me that if you think you understand quantum mechanics, then you don't understand any of it at all.

The mathematical portion, vector mathematics with imaginary numbers, was the only part that was interesting to me. It seemed to me that mathematical deductions were necessary because the phenomenon modeled nothing in our "reality."

Re: Quantum Mechanics for Programmers

#29

Earlier quoted context omitted.

I'm a quantum physicist (well, we don't say that, I'm an atomic physicist, but for anyone not aware it is 99% quantum mechanics we do all day), and the MWI isn't universally accepted, but it's not universally rejected either. Plenty of important physicists interpret quantum mechanics that way, and I do too (I am not important though). That's not to say I'm confident it's correct , just that it's the most sensible way…

> Furthermore, plenty of physicists don't actually grasp the fundamentals of their own field - they specialise a lot and can use specialised theories to get what they need done without understanding in detail where it came from. This. Sometimes physics does feel like a religion. The fundamentals (including basic assumptions and "proofs" that are complete bs in the mathematical sense) are getting reiterated time and a…

I completely agree, and I would say that's probably the historical origin of the Copenhagen interpretation. It was clearly initially a note-to-self that something wasn't right and required figuring out, and somewhere along the line that confusion became an axiom that later generations just accepted, not getting the message that it was unfinished.

Physicists aren't dumb, but they just haven't looked into it more because it's surprisingly not relevant to the majority of work. So they're just repeating the confusion of past generations as if it's fact.

But, particularly in my field, we're getting seriously good at manipulating more and more exotic quantum states. I'm working on things involving 'weak' measurement, where you really need to know what counts as a measurement or not, and how much - you can do a partial measurement and only partly (appear to) collapse a wavefunction. These types of experiments are becoming more are more common, and it's happened a few times now that I've heard people saying "hang on, what counts as a measurement in this context?" and then having to read a decoherence textbook in order to do their atomic physics.

With these sorts of things as well as quantum computers, decoherence and the measurement problem is intruding into a larger proportion of people's work, which means repeating the mantra of the previous generation isn't going to cut it anymore, people are going to actually read decoherence textbooks and decide for themselves.

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