Quantum Physics is So Weird that We Need to "Interpret" It.

The theory of quantum physics has existed and grown for more than a hundred years. And in that time it's extremely, ridiculously, successful at predicting how the universe around us behaves. But there's one small problem with it. It makes absolutely no sense, whatsoever.
Quantum mechanics, like other theories, is based on mathematical assumptions or "postulates". In this video we look at two such postulates. We can then look at mathematical consequences of each postulate, and test this against what actually happens in real life. If our experiments agree with the "consequences" we calculated earlier, then there's a good chance that our mathematical model represents our universe pretty well.
One postulate of quantum mechanics states that any system we study can be completely described by a mathematical function known as a wave function. It also says that the square modulus of the wave function is directly related to experimental probabilities (such as the likelihood of finding a particle in a particular region of space).
It's not fully clear to us yet why the wave function is related to measurement probabilities in this way - quantum mechanics doesn't tell us this, as it's only a mathematical framework.
Another postulate states that the mathematical equivalent of making a measurement is to apply an operator to the wave function. Again, the WHY behind this is unclear. But the math does work out, in that our experimental results do really seem to reflect how measurement operators applied to wave functions behave.
Because there's a lack of clarity between our mathematical framework, and the actual inner workings of the universe, but at the same time the math is so strong at accurately predicting how our universe behaves, physicists have tried to come up with different interpretations of quantum mechanics.
The one we've been working in so far is the Copenhagen interpretation. It's also worth noting that quantum physics seemed to break otherwise important "rules" of physics. For example, in relativity, one part of any system could only communicate with another as fast as light (or other EM waves) could get between them. However in quantum physics there seemed to be an instant way for particles to communicate with each other in some instances.
One interpretation of quantum mechanics, known as the Transactional interpretation, tried to solve this problem. The idea behind this is that each part of any system we study will send out wave-function-like waves both forward and backward in time. The waves from different parts of the system meet in a "quantum handshake". This is what decides what experimental result we will see in each case, and there's no instant transfer of information.
Another interpretation that solves the probabilistic nature of quantum mechanics is known as the Many Worlds interpretation. This says that every time an event occurs, the universe splits into multiple other universes, one in which each possible outcome occurs. For example, if I took a test then in some universes I would pass and in others I would fail.
Interpretations are very interesting to think about, but so far there aren't really any ways to test them experimentally in our universe. So for now, they remain theoretical concepts.
Further Reading:
Transactional Interpretation - en.wikipedia.org/wiki/Transactional_interpretation
Many Worlds Interpretation - en.wikipedia.org/wiki/Many-worlds_interpretation
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Chapters:
0:00 - The Basis of Quantum Mechanics
1:16 - Postulate 1 of Quantum Mechanics
2:58 - Do We Know Why This is True?
3:54 - Postulate 2 of Quantum Mechanics
4:25 - Why Do We Stick with Quantum Mechanics?
5:27 - Copenhagen Interpretation
6:26 - Transactional Interpretation
7:56 - Many Worlds Interpretation
Cards:
6:21 - • EPR Paradox: EASY Quan...

[@garuna666]

Parth never fails to cook

[@S.A.7891]

Hi Parth, I would appreciate if you can do a video about what is “phase in degrees” in magnetotelluric MT ? MT is a passive electromagnetic method that are based on Maxwell’s equations which you partially explained in one of your videos? I have not seen anybody yet to explain it correctly! They all say a sentence about it and that is it! I think it is a gap that needs one of your brilliant illustration videos. Thank you.

[@Physics_seeker]

kzbin.info/www/bejne/fHK9YmehZddjpdksi=O-ILkIpVnYS6tCv1

[@markbothum4338]

The problem I have with Many Worlds is that taken to its logical conclusion, every dang particle in the universe has probabilities, so every particle has been "creating" universes every unit of planck time...for 13.8 billion years. That's not just me not "thinking big enough", that's just downright unlikely. And if you want to limit that to, "Oh, it's only when a measurement is made", then tell me who's deciding where to draw the "measurement" line. My dog makes measurements. Viruses make measurements. Gas particles make measurements. Atoms make measurements. Electrons make measurements...it's a deep rabbit hole.

[@user-sl6gn1ss8p]

I've seen it explained as not so much making new worlds, but like "bundles" of possible getting progressively incoherent between each other, with "collapse" being this "separation" of previously coherent possibilities. So in a sense I guess there's wouldn't necessarily be any "creation" going on.

[@markbothum4338]

@@user-sl6gn1ss8p Yeah, Sean Carrol gives a pretty similar explanation. I was talking absolutely worst possible case, which probably isn't fair, or even an accepted interpretation. Maybe I'm just annoyed at the possibility there's another "me" lounging on a beach instead of going outside to get more wood for the stove.

[@GGoAwayy]

As for measurement... think of it instead as causality. What can affect what, given relative positions in space and time. A human observer measuring a quantum effect... means the quantum effect is having a causal effect on the matter of the measuring human. Whether the effect was an actual measurement, or was seen but never thought about, is irrelevent. Since its just cause and effect, theres nothing special about the effect being on living matter vs inorganic matter. The universe as a multiverse is then an expression of every possible event, and every possible following chain of events. All the possible ways the story of matter and energy can possibly be played out.

[@Zamicol]

Action is a less cumbersome word than measurement.

[@ParthGChannel]

Yeah - very valid points here. I'm not sold on many worlds myself, but I'm not sure if that's because it's problematic or because I just don't understand it well lol

[@thehappypittie]

You and PBS Spacetime are hands down my two favorite science channels. Your ability to break things down to such simple descriptions without losing the plot is invaluable for a hobbyist trying to understand these things even if only at a high level.

[@ParthGChannel]

That's some high praise! Thanks very much :)

[@thehappypittie]

@@ParthGChannel You deserve it my man

[@dimitrispapadimitriou5622]

6:00 That doesn't mean that information is exchanged between spacelike-separated events A&B. No- signaling theorem. Entanglement is about correlations , not about sending information faster than light...

[@gavinfinch2393]

Can you explain further please? I’ve always heard it explained as faster than light interchange.

[@marcosmarroquin1821]

5:08 “stuck its weird wave particle tongue out on us” made me giggle 😭 i literally got infuriated this entire quarter learning quantum mechanics

[@mintakan003]

Nice explainer video, on the issues involved. Some other notes. Math sometimes has a "Platonic" status, for some physicists. It's not just a convenient model. It suggests something more intrinsic in the relationship between math and reality. But if one is coming from a data science background, math is just a tool. It's kind of a mercenary view. Data scientists know that their models are a statistical approximations. For physics, the claim is the relationship is much tighter. The other issue is asking which intuition of how reality should be, is more fundamental? Is it quantum mechanics? Or is it based on our macro bodily existence, mainly based on (classical) space+time existence? Our fundamental intuitions of reality, is based on how our macro bodily existence "groks" things. Even if the actual reality (QM) is different from this intuition, I get the impression we try coerce this into some version of local realism, be in transactional reality, or multiplying versions of classical reality, in "many worlds". Our local intuitions maybe wrong (at the deepest level). But we try to make sense of things, on those terms. (This is getting into issues of epistemology, and cognition.) So I wonder, am I'm articulating a view for "shut up and calculate" (?). (Also, the Copenhagen procedure is good enough for most purposes. (?))

[@sjzara]

A Platonic aspect of mathematics makes no sense. Mathematics is abstract and doesn’t have any causal aspects.

[@car103d]

Sheldon’s favorite interpretation

[@aryan0029]

Bhai explain poynting theorem plz

[@zeroonetime]

Q.M.Telepathy I.S. Information System - 010 Gravitational Propulsion System -- GPS.

[@thespecialkid1384]

Interesting

[@SampleroftheMultiverse]

Cannot find me

[@dimitrispapadimitriou5622]

The many worlds interpretation is weakly non local exactly as the "standard" interpretation is. All interpretations are. Locality, by definition, is a property related to the physical four-dimensional spacetime ( not abstract configuration space or anything else). So, each individual " world" that corresponds to an individual branch in the MWI is non- local just like in Copenhagen interpretation, no more no less...

[@PrzemyslawSliwinski]

8:37 - so there is a universe in which quantum experiments are always five sigmas away from the theoretical predictions?

[@GGoAwayy]

Theres a universe where quantum computers have never given a good answer to any calculation.

[@ParthGChannel]

If the many-worlds interpretation is correct, then probably. I guess just because many worlds implies the existence of many (even infinitely many) universes, doesn't mean that every single possible configuration of universe MUST necessarily exist... but I may be wrong about that. Either way, an interesting point to think about!

[@DrDeuteron]

The equation at 4:21 is only true is psi is en eigenstate of the operator.

[@Oliveir51]

I believe QM is not complete. It does not say about the detector that should be ideal.in addition to what you mention. Ideal detector no time... those must be assumed

[@Physics_seeker]

If Quantum physics fascinates you then this channel is for you kzbin.info/www/bejne/fHK9YmehZddjpdksi=O-ILkIpVnYS6tCv1

[@lepidoptera9337]

You are barking up the wrong tree. An ideal detector is an irreversible process. Irreversible processes take an infinite amount of time by definition.

[@BASANAGOUDABELLIKATTI]

Hi bro 👋 , Thank for your as most best explanation to us ❤. As I am science student I understood it clearly. And because of your awesome explanation 😊❤. I request ❤ you bro to make the videos in another language like Hindi. Because it helps lot of us and specially who are not belongs to science field ❤. I hope you make the videos soon in Hindi 😊😊😊😊😊. Thank you for reading my comment 🙏🙏🙏. If you agree ❤❤ for my request give like 👍👍👍 to my comment 👇👇👇.

[@milkwater1204]

Funnily enough, I just wrote an essay about the many worlds interpretation for a second year QM assignment!

[@jamescollier3]

I wrote it for you in another universe

[@milkwater1204]

@@jamescollier3 drat... I thought I was the only person who could remember alternative universes...

[@TerranIV]

Ptolemaic calculations produced much more accurate predictions than Copernicus's model. So just because a mathematical model predicts outcomes, doesn't mean that it contains any inherent truth about the universe. There are no multiverses, just like there are no epicycles.

[@anonymes2884]

8:44 "The trouble is..." Sure but then that's _also_ true of the Copenhagen interpretation. The only actual "evidence" for a physical process of collapse is, the wavefunction provides _multiple_ statistical _possibilities_ but we only ever measure one. And obviously, that's not evidence of collapse at all, it's just saying "We don't know how but we know it happens so we made up this entirely aphysical process to explain it" (and no, decoherence _isn't_ the physical process of collapse). We might as well have said "Fairies do it". (i'm fairly convinced that the only reason Copenhagen doesn't seem as weird to us as e.g. "many worlds" is because it's the interpretation in all the textbooks - we "grow up with it" so we don't always really think about how weird _its_ claims are)

[@dimitrispapadimitriou5622]

The Wavefunction in the standard interpretation is not a "real physical wave" (whatever that " reality status" means) that "objectively collapses" ( as in GRW or other physical collapse theories). It's only an accurate mathematical tool for calculating Probabilities from amplitudes. For the physicists that are more sympathetic to the standard interpretation ( or the more modern versions of it like Relational QM) , collapse is epistemic, not objective. Probabilities are fundamental and irreducible. By the way, the same essentially is the case with the MWI, for each individual branch: Again, each observer finds herself in a randomly "chosen" "world" and this ( irreducible again, because there are no hidden mechanisms or variables in MWI) randomness appears only at the macroscopic level, of the measuring devices etc., the same with the Copenhagen. So, you don't gain anything by assuming that different branches of the Wavefunction correspond to different semi-classical "worlds".

[@dimitrispapadimitriou5622]

@@armandaneshjoo I have noticed that myself. It doesn't happen very often, but the weird thing is that it doesn't occur for "insulting" or pseudoscientific woo woo - kind of comments. It occurs sometimes when someone's trying to explain a bit standard textbook physics, responding to inaccuracies etc...

[@dimitrispapadimitriou5622]

@@armandaneshjoo This is a typical disagreement between Ψ- ontologists ( like you) and those ( like myself) who think the Wavefunction as an abstract State Vector in an abstract mathematical (Hilbert) space that describes ( some aspects of ) reality, but it is not " the basis of reality" itself. For those who are Not "Ψ-realists", the "Wavefunction realism" seems like a typical "category mistake". Think about this analogy from classical physics: the Riemann Tensor in General Relativity is related with the intrinsic curvature of spacetime. It is a mathematical tool that measures the deviations from zero curvature ( flatness). Zero intrinsic curvature: zero Riemann Tensor . Curved spacetime *Is real* . The Riemann ( and also the Ricci, Weyl) Tensors are mathematical objects that describe reality. The world is not *made* from mathematics ( as Tegmark e.g. believes), it is *described* from mathematics. - I totally disagree about your interpretation of Probability in QM. In the standard theory is fundamental, irreducible and unavoidable! Only in Qbism, or the Deutch/ Wallace version of MWI probabilities are considered "subjective". But in those interpretations they need to assume the fundamental " primary" existence of conscious observers ( that make decisions or bets) and this is a circular dead end: Because observers are emergent, not fundamental, they are described by the same laws of physics like everything else!

[@dimitrispapadimitriou5622]

@@armandaneshjoo The same happened again! My detailed response to your comment " disappeared mysteriously"... I won't do it again in detail ( it seems that commenting on KZbin is a waste of time...): - I'm not a Ψ- ontologist person. The Wavefunction is a mathematical object (a Vector in Hilbert space) for calculating Probabilities. The Universe is not *made* of mathematics, it is *described* by them. These Probabilities are fundamental, irreducible , unavoidable in the standard theory. Qbists and some MWers ( Deutsch/ Wallace) are thinking Probabilities as subjective , but this is circularity, because it assumes the existence of observers that make "bets" etc, and these observers have to be described in principle by the same laws of QM... vicious circle.

[@ParthGChannel]

I think you make a good point tbh. I really hope we can get some clarity on this within our lifetimes.

[@brogottime239]

Hey parth I have been watching ur videos for a very long time , would u pls try explain the equation of lass 11th and 12th of Indian cbse board

[@ParthGChannel]

Hey thanks for the support! Any specific ones?

[@RobertLeitz]

"Euclid's Cat"..Here are the basics for the speed of light colors..B & W Are E.P.R. Same Line Instant..Black = Instant Future Certainty..White = Instant Past Uncertainty..Universe Started Black "Lost Time"....There is no green or orange..Only Yello"Euclid's Cat"..Here are the basics for the speed of light colors..B & W Are E.P.R. w on top of blue...Or Yellow on top of red..Euclid compared to Schrodinger's Cat...Postulate 5 = Blue = Future Uncertainty.."Universe Start"..."Lost Time"...Postulate 1 "Green Door In"...Postulate 2 "YELLOW/CONSCIOUSNESS"...It is On TOP..Joining 1 + 3 Together....Postulate 3 "Orange Door Out".....Postulate 4 Red = Past Certainty...."Completeness Of The Time Tick In The Classical World We Know"....Purple = Infinity..Take Care...Bye....

[@GGoAwayy]

Another good video. But after watching all I can think about is how much that Batman logo looks like teeth in an open mouth.

[@ParthGChannel]

Can't unsee it now :'D

[@deltalima6703]

Its a shame that interpretations are currently barren of side effects.

[@zak2659]

No love for relational quantum mechanics 😔

[@lepidoptera9337]

The statement at 2:20 is completely false. The wave function does not describe one system. It describes a quantum mechanical ensemble of systems. An ensemble is an imaginary an infinite repetition of the same experiment. In other words: the wave function is an abstract quantity that we form as a description of experiments as an extrapolation of frequentist event counts. It does not exist in nature. The statement that the square of the magnitude of the wave function gives the probability to find a quantum in a certain region of space is also false. It's a mis-interpretation of the Born rule for the special case of a unity measurement operator AND assuming that the wave function is in a spatial representation. That statement is, unfortunately, being reprinted way to often in introductory QM textbooks, but even an undergrad student should have enough intuition to catch the problems with it. No offense, but I wish the people who try to teach quantum mechanics on the internet would, at least, take the time to learn the basics of quantum mechanics.

[@joachimkeinert3202]

yes, if a theory is not testable it's just speculation, maybe.

[@poglord._]

cool, i never thought of it that way

[@telotawa]

no

[@ParthGChannel]

no u

[@aelinwhitehorn3526]

is it me or does he look like ram charan

[@ParthGChannel]

That's a pretty big compliment lol thanks

[@derhamcohomology]

No, it doesn't.

[@ParthGChannel]

Yes it does. ... or does it?

[@rhodium8505]

i think you spelled "Parallel" wrong in the title of the video

[@RobertLeitz]

If you were in a room..With a normal window moving @ light speed forward..."The Window Is Too Big To Steer Through The Blurry Future"...."Create A Sensible Focused Time Gap"...So "Block Up The Window".."Make A PinHole"..And "Steer From The Upside Down Past 20/20 Hindsight Rear Wall Image"...→ > -|- < → You can "Steer" from a "Clear Rear Window Too"..Either Way..??.."Hindsight Is The Best Guide To The Future"..."The Rear Wall"..??.."Is The Only Wall That Will Make Sense"...Take Care...Bye.. "Observation" Is E.P.R. Euclid's Straight 5th "Instant".."If You Snooze You Lose"...Look at your bed sheets..How long are they going to last..??..."Then Think Of The Magic Light Sheets"..Like..??.."The Magic Grits".."Traveling Billions Of Years"..."Getting Hit Left & Right By Other Magic Light Sheets"...(Sock/Bam/Pow)...."Just To Arrive A Billion Years Later"..."Excellent Quality".... "For You To See"....Take Care....Bye....