Photons and the loss of determinism

MIT 8.04 Quantum Physics I, Spring 2016
View the complete course: ocw.mit.edu/8-04S16
Instructor: Barton Zwiebach
License: Creative Commons BY-NC-SA
More information at ocw.mit.edu/terms
More courses at ocw.mit.edu

[@luisangelespinozahumberth1016]

Que nivel de clase de este profesor . Orgullo peruano .

[@elitedelobos]

No es peruano es Judío Ultramar. Judío ...

[@juanrodrigovalencia]

@@elitedelobos Puede ser de origen judío, pero nació en Lima, creció y estudió en Lima, graduándose de la Universidad Nacional de Ingeniería. Es recontraperuano

[@elitedelobos]

@@juanrodrigovalencia No. El siempre la tuvo clara. Es un judío y tiene nacionalidad judía.

[@juanrodrigovalencia]

@@elitedelobos En serio? Y tiene pasaporte "judío"? Por favor JAJAJAJJAJA

[@ginnopuma]

​@@elitedelobosmira mongol si Vienes a opinar sin info mejor ni opines lapiz😅

[@BiscuitZombies]

This is brilliant. This professor explains things extremely clearly.

[@BeckBeckGo]

Agreed totally. His pacing also is fantastic

[@prototype8137]

Lol.

[@RobH.]

He is a pseudo scientist!

[@tanishqbagria5459]

I'm 12 and I got it too

[@08C6PaceCar]

Does he tho ?

[@marcocarrasco6037]

Barton, el único estudiante en la historia de la UNI que se graduó antes de terminar su carrera.

[@mayimbu6662]

El mejor alumno de la historia de la UNI.

[@ARCP-mj1mr]

Es de mi facultad

[@paultarazona7989]

​@@ARCP-mj1mrq nunca lo ejerció

[@joser.9827]

​@@paultarazona7989XD

[@omargclb]

​@@paultarazona7989😂😂

[@cesarrolandorumichehernand2643]

Buena la profesión le sirvió para hacer investigación, dónde invierten otros países extranjeros.

[@volcano868]

the clue is in the title guys - Open Course. For anyone who wants to watch. And you've got to be pretty good at your subject to explain quantum physics so that anyone can even approach understanding that!

[@moinmalik1320]

Besides the wonderful clarity in his lecture, I am amazed at his very clear, beautiful, and organized writing on the board.

[@petrok1rp254]

Such amazing job Mr. Zwiebach! Thank you...

[@pity4777]

Well spoken with excellent handwriting. A rarity among physics professors

[@BSP20101]

"It's a debacle! A total disaster!"

[@milind-9683]

thank you MIT, thank you sir, and thanks to whole staff there.

[@mohammadasefhossaini7985]

Thank you MIT and sir. Wish him long life and happiness.

[@RC-uo3ds]

Brilliant lecture given by Barton Zweibach Sir .....

[@gregsg2351]

This lecture has nothing to do with me but I became entranced with his style and voice! And I actually learned something new in quantum theories. Thank you Sir.

[@manaoharsam4211]

Great Teacher. Takes time and explains well. Defined indeterminism very clearly.

[@ralphdams7568]

What a wonderful teacher you are, if I may say so. Thank you for sharing this lecture with the public. 🤓

[@StarNumbers]

A shill can only repeat the obvious -- it's in the public.

[@ralphdams7568]

🙂

[@eastwestcoastkid]

Bertrand de Born really?

[@eastwestcoastkid]

Bertrand de Born I’m sorry MIT is one of the preeminent science and engineering schools on the planet. So this professor has earned his position in that esteemed University. Have a nice day. Also no one ridiculed anyone-I think you’re projecting-and I’ve learned quite a bit thank you much 😃😉

[@eastwestcoastkid]

Bertrand de Born oh please-try this-why don’t you go to Feynman’s lectures in Physics and start reading at volume 3. You learned this in 9th grade huh? I doubt it. This is Quantum Physics-you did not learn this in 9th grade. Go to OCW, and look at the ENTIRE CLASS genius. Tell me, why do you have to use the renormalization group in Quantum Electrodynamics? How do you know you understand English? Fella, you lost all credibility when you questioned the status of MIT. All credibility. Have a nice day, remember not to go out as you don’t want to be exposed to SARS-Cov-2 and get COVID-19. There’s a good fellow. G’night 😉😃👍. Oh and we are done.

[@vector8310]

This exposition is as clear as can be

[@pmo1972]

"That's what polarizers do for a living" :)

[@flossenking]

lol

[@xtra-oi9xb]

.... what percentage of polarizers are unemployed .. that's what I wanna' know ... it seems the good professor overlooked this dilemma during the lecture ..... hmmm .....

[@MikeSmith-cl4ix]

The polarizer proves that light is a wave and not a particle.

[@MikeSmith-cl4ix]

@Phoenix do you think Trump is a real president?

[@MikeSmith-cl4ix]

@Phoenix when the Suits come for you, don't answer the door.

[@ramonasosna]

I definitely agree when you mentioned that it's good to learn from physicists and it's useful that we have them, it is good to make new explanations for what comes next.

[@SatishSingh-mk7jq]

Thank You for making it understandable !! I am a software engineer in network domain. I just watched these videos(first 4) out of curiosity, and I was able to understand a rough picture of what's trying to be conveyed. Last time I studied physics was in pre-college days.

[@andressuarez6153]

peruvian's proud!

[@richardmakiya7188]

​@@andressuarez6153 así es.

[@victorcortez479]

Si estuviera traducido al español, seria genial. Excelente Profesor. La UNI siempre destacando.

[@luchomarrano]

Lo cierto que la UNI no hizo nada por él, pudo haber estudiado en cualquier otra universidad e igual hubiera sobresalido, más bien la UNI debería estar agradecido de haber acogido a una mente tan brillante

[@s0ulseeker.]

Aprende inglés en vez de perdir subtitulos, por eso los egresados de la uni muchas veces terminan enseñando de profes en academias 🤣🤣🤣

[@AlexanderBlow]

Ese Barton solo copiaba en la uni yo lo conozco le ponían 20 los profes solo porque su viejita era bien bandida la prra😅

[@Diego.Andree]

​@@s0ulseeker.? Por no aprender inglés?, mano como en toda u siempre hay gente que no ejerce su carrera.

[@Diego.Andree]

​@@luchomarranoconcuerdo

[@Unambiguously182]

I really like his handwriting This looks so passionate

[@Tensoren-yj9ux]

In that case I advise you to check out Nima Arkani-Hamed.

[@italoperezcifuentes6068]

This professor was a former student of one of the best universities in Latin America, the prestigious National University of Engineering (Peru). He was not your average student or teacher. He is a living legend, a GENIUS. Feel privileged to receive their knowledge in your country. Saludos 🇵🇪

[@renzosanchez4732]

No me di cuenta de que era barton, such a precious gem of our country. It's a delight hearing his class

[@katyvaldez8890]

Si bien la UNI es una de las más díficiles de ingresar en el Perú, no es una de las mejores universidades de Latinoamérica, de hecho, en rankings de universidades, no llega al Top 60 de Latinoamérica. No es por desmerecer nada, pero las cosas como son. Y sí, el profesor es un genio.

[@fernandoalejo]

JJAJAJAJJ prestigiosa por donde wbonazo

[@Diego.Andree]

No exageres man, no es de la mejores de Latinoamérica pero si tiene su prestigio

[@McCarthy_Was_Right]

you will never be wh*te

[@evcman4383]

Man, I just enjoy listening to his voice....

[@oussamaaljarroudi9724]

Me tooo I swear to God 😄😄😄😄

[@lesubtil7653]

I can tell he is a good teacher because I understood this little "lecture" better as when my teacher taught me the same subject, even if my teacher spoke my first language (french), and this teacher speak english, that is harder to understand for me.

[@rajinfootonchuriquen]

In some sense, the fact that he is peruvian and has as first lenguage the spanish, it make him use simpler words to do his lectures so it's easy to follow him in his thoughts.

[@user-ie2ur4ry5t]

Good and clear teacher. Good tempo and very to the point.. Absolutely well done and definitely keep it up!!! .

[@ryanrizzo3866]

Thanks for the lectures!

[@fjs1111]

This professor is one of the best

[@sell_or_stfu8405]

Wow. The universe it truly random. Thank you.

[@juanjoseph7180]

De los mejores profesores de física.

[@tayfun11100]

Thank you Barton Zwiebach and MIT.

[@barryzeeberg3672]

just now found this by chance - he is excellent. if they make a movie about him, he would be played by Dustin Hoffman.

[@user-tt2po5wg7n]

Well spoken with excellent handwriting. A rarity among physics professors. Maravilha de aula! Eu diria um pacote de fótons de aula! Parabéns!!.

[@justinkane290]

Wow, clearly explained and at a pace I can work with. Gonna be watching more of these.

[@suyrai4u]

Now I understand What entanglement actually means ! Extraordinary explaination

[@keepgoing335]

there's something about writing on a chalkboard that just makes it much better than presentation slides as a teaching medium for showing equations

[@pellythirteen5654]

Good and clear teacher. Good tempo and very to the point.

[@jeanlacombe3606]

Merveilleux cours de physique ! Merci de partager toutes ces explications si claires 👍

[@brainstormingsharing1309]

Absolutely well done and definitely keep it up!!! 👍👍👍👍👍

[@wulphstein]

Glad you figured out that determinism is voluntary.

[@PauloOliveira-pq3qr]

Maravilha de aula! Eu diria um pacote de fótons de aula! Parabéns!!

[@jairofonseca1597]

This must be the best lecture on loss of determinism on the net, much thanks.

[@StarNumbers]

You lost determinism when you flip a coin. Write parents to send more money.

[@nassimabed]

I've seen better

[@aravartomian1]

No

[@brivda]

@@nassimabed care to share the better video?

[@nassimabed]

@@brivda I had written that comment a month ago. I have no recollection what this video was about or what other video I was thinking about. Not to mention KZbin won't allow video comments.

[@sergioortiz8219]

With all those smart guys at MIT, you'd think someone would've invented a self-erasing board by now.

[@BeckBeckGo]

Like an iPad?

[@BeckBeckGo]

These guys are old-school. They probably prefer the feeling of the blackboard

[@mmmk6322]

Can't do dotted lines without a blackboard.

[@mydogbrian4814]

- Professors need exercise too!

[@RobH.]

@@BeckBeckGo naa just old school pseudo scientist/mathematicians propogating their bullshit lies to anyone who will listen!

[@georgestuart8656]

What a lovely man. So calm and precise. I remember being introduced to Imaginary numbers at school. POW. Mind blown. Two years later in college, they're vectors. Oh. Why didn't they say that ? On a par with year 2 maths class. Ok. Let's consider n. n is any number ! Pow. n is clearly a letter. Dropped out of the top maths class soon after. Got back in again though. Just the whole year missed and forever holding on by my finger nails since.

[@apolloniuspergus9295]

Well, the bell inequality just shows that you cannot have both a local and hidden variable theory combined. If you have a hidden variable theory, it has to be non-local, and if it's local, it has to not rely in hidden variables

[@Krish_202]

Yeah pretty good argument 🤷‍♂️

[@hansenchrisw]

Thank you. Was about to make a similar comment. Bell himself was a proponent of Pilot Wave theory aka Bohmian mechanics. A completely deterministic, nonlocal, hidden variable theory.

[@cesitarc.4490]

Barton Zwiebach the genius from Perú.

[@Carlos_Sernaque]

La leyenda de la UNI-PERU , Barton Zwiebach👏🏻👏🏻👏🏻

[@BlochSphere]

So with respect to Linearity discussed in previous lectures, Beam of photon should be described as Beam |photon_alpha> = a * cos_alpha * |photonX> + a * sin_alpha |photonY> Where a is some constant

[@jamshidfaiz6705]

Absolutely brilliant. Thank you for sharing.

[@alexandervassilev6702]

Excellent professor

[@smalin]

What are all the physical processes (besides the behavior of polarized photons) that are non-deterministic? Is radioactive decay non-deterministic? Is there a complete list of non-deterministic processes somewhere? Are all non-deterministic processes somehow the same process at their core?

[@eastwestcoastkid]

smalin yes as quantum mechanics describes radioactive decay-yes. Same process at their core? Only in the sense that they are part of the class of non-deterministic things. Ah the point behind quantum mechanics and quantum theory is that what we think as determined is at base, not deterministic.

[@trafalgarla]

It's not an easy question to answer because what is deterministic (or whether anything is deterministic) depends on which interpretation of quantum mechanics is correct and we don't know which one is correct. For example, everything is deterministic in the Many Worlds interpretation, including radioactive decay, since the wave function describes all possible events. Questions about determinism are usually left to philosophers of physics nowadays so the Stanford encyclopedia of philosophy is a good starting point to read up on some of it. plato.stanford.edu/entries/determinism-causal/

[@francoisdeletaille]

@@eastwestcoastkid In my view It is the instant (now) that determins reality, on the base of what is determined previously. So that the instant is not completely severaged. By this, I do not means that the instant acts upon reality, but that it is the concrete manifestation of everything that takes place in the instant. Continously. But "free".

[@eastwestcoastkid]

francoisdeletaille that is an interesting philosophy-but at base Quantum mechanics and Quantum theory hold that physical reality is not deterministic-hence the uncertainty principle.

[@francoisdeletaille]

@@eastwestcoastkid I think we agree. At some point, reality is determined (observed). But it remains open.

[@sgsmozart]

Wow !...A professor who writes cursively ! 🎊🎉🎊

[@Thighwatts]

A good university isn't just made by the sum of their students' success but by the ability of their professors to teach and simplistically explain complexity!

[@Adityarm.08]

These lectures are awesome!

[@user-ul7xl7jq3w]

There is a difference in the way of thinking of the inequality sign (or information bra-ket) when we see light as Einstein inertial system and when we see light as quantum entanglement information. Is a very effective inertial vector. In quantum information entanglement, since it is not an inertial system, it is considered as |photon:〈xψy〉:photon｜, and it is an information system that should be distinguished from the inertial system, but (photon:ψ>)=(photon: :ψ〉), the optical inertial system and the optical information system are equivalent. This is an important lecture from the perspective of consideration.

[@sucersdungeon]

A great speaker. An inspiring video.

[@yoshirovilchez3392]

Grande Zwiebach, recuerdo que nos metiamos unos dotitas en el lab despues de los finales

[@josiaszapata6984]

XD

[@Diego.Andree]

XD

[@r__9_1____a34]

He said that hidden variables are not possible, but bells theorem says local hidden variables. Nonlocal ones can exist

[@zack_120]

11:00- Really true, consistent with the wisdom there are more unknown unknowns than known unknowns. 15:25- This statement makes the superposition concept a bit easier to comprehend.

[@schmetterling4477]

Nothing he says explains to you where superposition really comes from. If I were to test you orally on that question, I could easily fail you, right now.

[@JetpackBattle-lc7ob]

I appreciate the fact he is saying what actually happens with the correct terms, instead of abstracting it all away. I watched a similar MIT lecture but the professor was using terms like "color and hardness" to avoid "confusing us" but for me it made it really hard to picture anything in my head and follow along cause electrons don't have "color" or "hardness" in the classical sense

[@lepidoptera9337]

That's an exercise to get students to understand that nature does not consist of phenomena that can be described by commutative algebras alone. It's the big insight of Heisenberg... except that he had to figure it out without help.

[@csjfd1764]

excellent explanation ! Congrats, professor !

[@smartscience5305]

Hello Dr. I am 12 years and this video was great , and I wish to be more specification and harder. Thank you

[@kskrishnasangeeth]

Great explanation

[@neoaureus]

So energising a lecture ! Wow

[@smcconnell2200]

Nicely done.

[@mikefredd3390]

Now I know what good teaching is. This is a strange world where we know so much but are somehow missing the point completely.

[@sandeepanand3231]

Excellent lecture!

[@debbiemccoig7672]

Love this I enjoy it even though I not ready for this

[@marktwain622]

It's nice to see MIT still using chalk boards, very OG.

[@idea2go]

Great lecturer, thanks for posting this

[@SanjayPandit-sc9xx]

Thanks sir for this beautiful lecture from India.

[@SanjayPandit-sc9xx]

Totally concept clear from this lecture.

[@dariopalomba8420]

Prof. Zwiebach is actually very good, but for any "not perfect English speakers", it was absolutely necessary the presence of subtitles....in English! Anyway, thank you for the lesson and greetings from Athens, Greece.

[@beggar1415]

116 dislikes show jealousy of not having best teachers like him

[@worldnewsfoodandbooks8218]

Looks like Harisson Ford

[@stevematson4808]

After the lecture he's going off to fight Nazis and discover stuff

[@stevematson4808]

Thats Harrison ford doing an accent

[@user-zk1dg4tu6l]

Does anyone know what experiments he is referring to when he mentions people have ruled out the argument "It is the unknown subatomic structure of the polarizer that determines which photos pass vs are absorbed?"

[@marcuspradas1037]

Brilliant indeed!!

[@michaelcheung6290]

He is brilliant

[@js-fx6vm]

The figure in this explanation would be better if shown in three dimensions. The professor’s explanation describes a plane wave oscillating in a plane parallel to the z-axis at an angle alpha to x--z plane. Then the closer the plane of the wave gets to the x-z plane, the greater the transmission of the wave through the polarizer.

[@charlesbromberick4247]

Very nice presentation of a very confusing reality.

[@CarlosLeon-ii2fs]

Increíble un ilustre Peruano haciendo patria en el extranjero.

[@rsalazar9784]

Porfesor Barton, alumno de la UNI - PERU.

[@betanapallisandeepra]

He is very good teacher…

[@ericpham4011]

quanta was energy unit measurement. if we can program photon in twisted wave guide. is there two type of frequencies minum to have light so should it be Frequency**2 ) * wavelength= speed

[@surendrakverma555]

Very good lecture Sir. Thanks 🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏🙏

[@sarojpandeya7883]

Amazing!

[@ryder1658]

Will Ferrell on particle wave duality

[@kundesumitha2942]

great lecture always great onlyyyyy.......hands offf

[@rogermarceloramirezramirez6120]

Barton

[@tomnoyb8301]

Polarizers are not filters, they are re-radiators. Imagine two antennas connected by a coaxial cable. The interfaces between glass and air are the antennas and the glass is the coax. Light impinges the front face, just as an antenna. If the antenna's polarization matches, the light enters the glass, propagates and exits according to the polarization of the back face (antenna) of the glass. Using this correct model of a polarizer explains polarization completely and without mystery. Bell's Theorem is not required, only Maxwell's equations.

[@AndreaCalaon73]

Bell just showed that a HVT is non local and, if the formalism of spin is correct, that it is also contextual. Look at the interpretation of spin in the works of David Hestenes and other physicists, and contextuality desappares

[@dougr.2398]

Bell’s Theorem and experiments with photons were the subject of my oral exam for admission to Doctoral candidacy in 1977.

[@dougr.2398]

The most interesting thing I found out about Bell’s theorem was that it was based on an error that J.S.Bell found in VonNeumann’s “Mathematical Foundations of QuantumMechanics”

[@eastwestcoastkid]

Doug R. What was the error, and did you do your Doctorate in Quantum theory?

[@dougr.2398]

eastwestcoastkid I’d have to review Bell’s collected published works (papers in scientific journals) as I believe it may have been referenced in at least one of his papers, and no.... I decided that an experiment was not necessary at the time, some years before Alain Aspect was funded for his own research, which found the expected result (in support of Quantum Theory). I eventually left Physics research, after switching to the low temperature physics group, and some five years after leaving that, left teaching for another career path.

[@IanHarrison-xo5kf]

Great lecturer

[@komolkovathana8568]

From Rene (Decartes)'s Materialism to Russell (Bertrand)'s Mechanicalism..our view on the Materialistic world was profound and set forth every Rational Aspect of our understanding. So we call the elementary ingredients study, the PARTICLEs Physics, due to Democritus 's undividable Atoms (though later we found many "p" are much smaller than 'P'). Light is particle called Photon, electric is classified as lepton, 900 times smaller than Proton (Neutron). Even binding Energy we considered them as Gluons-exchanged ? And same as gravity, forcefully we try to MAKE such Interaction as GRAVITON exchange process, another kind of tiny(minute) PARTICLE as well. All were found by materialistic view of the universe, Interacted together with some deterministic MECHANISM, either exact or by STATISTICS (that You consider it UNdeterministic.)

[@johnpepin5373]

So... does that mean photons are constantly changing states, (polarization but not frequency?), before they are measured, because they exist as a wave function? Is that why when sent through one at a time all go through or none do? Moreover, why is it that when polarized light is sent through three polarizers, at right angles to each other... some light gets through? Is it because since it is not measured, some photons in the wave state change polarization between polarizers? Then why do three allow passage but two block all light? Plus why is it a wave function rather than a matrix of possibilities?

[@abrahamgonzales6263]

Orgullo latinoamericano .

[@amirminayijalil6548]

Even Bell himself didn’t think that he proved the impossibility of hidden variables. Travis Norsen: in his book (titled ‘Foundations of Quantum Mechanics’) says: “There is a kind of rich and tragic irony here, in citing Bell as having supposedly refuted hidden variables theories …, Bell’s theorem was actually inspired by Bohm’s 1952 pilot-wave theory papers, and indeed Bell remained far and away the pilot-wave theory’s greatest champion until his death in 1990.”

[@zhyfn9773]

are coefficients cos (\alpha) and sin (\alpha) sort of fitting parameter then? or do they have a theoretical origin given alpha is the state prescribed to this classical state of polarization?

[@johnaugsburger6192]

Thanks, I had to switch on the physics neurons and watch it twice, but I get it.

[@XXX-tw6zm]

Isn't the wave/particle theory of photons the essence of the schroedinger's cat thought experiment? it seems to me photon detection by the retina is deterministic but the perception of it by our brain (and us by extension) is metaphysical

[@Obladgolated]

What if _i_ - the imaginary component of the wavefunction - is the "hidden variable" that Einstein theorized might be present for photons? I mean, it isn't unreasonable to expect the _i_ component to have _some_ physical manifestation, is it?