Mach-Zehnder interferometers and beam splitters
ฝัง
- เผยแพร่เมื่อ 4 ก.ค. 2017
- 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
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your videos used to reach me after I search for something in Quantum Mechanics. Now, they are always in the recommended videos and I watch some of them just for fun. Very clear explanations. Thanks a lot, Professor.
Professor Zwiebach is awesome, then again would expect nothing less for MIT
Absolutely well done and definitely keep it up!!! 👍👍👍👍👍👍
This is great stuff because you can play around with the maths yourself and learn more by doing so.
i know it is pretty randomly asking but do anyone know a good site to watch newly released tv shows online ?
Absolutely well done👍👍👍
BS is a mirror matrix (det=-1) , but the rotation matrix (det=1) could also work.
6:19 did a physicist just say ask an engineer?! Lol
Excellent lecture Sir 🙏🙏🙏🙏. Thanks 🙏🙏🙏🙏🙏🙏🙏🙏🙏
at 9:10 cameraman had a nap:)
Who is the one disliking this?
This Beam splitters matrix is mad.
this is very interesting but what if u share some exercices corrections and harder stuff
woderful explaination
If I use the [1,1;1,-1] for a BS, how is the phase of scattered state of [1;0] be different than [0;1] in the way that one acquires a negative one in the case of [0;1] but both are positive in the case of [1;1]?
At 14:34 he cleans the blackboard and later starts coughing because he breathed in all the chalk dust. Please use also water to clean the BB. It is unpleasant to watch you damaging your lungs.
🤣 lol man
jajajajjajjaj
Plz explain the calculation at 12.38
sir,
what is the physical interpretation of having a negative number in the Beam Splitter Matrix.
means nothing different from a positive value in terms of probability, just a phase shift of e to the i*pi
phase shift !
If somebody could help me:
at 11:41 he is justifying the choices on the matrix's elements and says that, because his first try (all = 1/2^(0.5)) resulted in a non normalized state, his proposed matrix for the action of the beam splitter couldn't be right. It just so happens that early in the video (or in a previous video) he states that the physics of measuring a particle in a certain state doesn't change at all by multiplying it by a factor, so why can't he just say this his previous (1 1)' is actually ('/2^(0.5))*(1 1)'? Going by his previous statement, this matrix could be validated... is it clear?
Well, from what I can understand, one doesn't really get (1/2)^0.5 × (1 1)'
In order to do that it's important to maintain equality within the equation also this is a superposition state and depends upon the initial states hence changing the new state means our initial state could not have been the ones we did use. It's like linearly independent (LI) states come together to give a new state, change the combination, you change the superposition state
Wouldn't the light passing into D0 have twice the amplitude due to the constructive interference, making the output light brighter than the light from the source? This is the part that kills me.
i think if you look at the problem with the classical wave model, than the beam splits its intensity at the beam-splitter (depending on the ratio of the beam-splitter) ... for example 50%/50% equals half intensity for each way. If you combine the to interfering waves afterwards, there should be no higher intensity. also important : the frequency is still the same (you would not notice a color change in the real experiment).
yeah the thing is the photon only superimposes with itself, not another photon because that would violate the conservation of energy. think this was covered earlier.
❤
Photon structure imagine in three phases
Circular - scalar
Longitudinal - vector
Junction - give rise to 3 and 4
And further
In
First rotation around a notional centre held by a veirtual centre
Creating
5 and 6
7 and 8
Back to 9
Then a repeat
Above some what spell out THEORY OF CREATION OF THE DIMENSIONS
The BS matrix turns out to be the matrix of the reflexion with respect to the axis that makes an angle π/8 with the (Ox) axis. What does this π/8 represents?
in this lecture is just assumption i believe
what happens if the (a,b) becomes (i,0) or (0,i)? this cases obey the normalization condition but is this state possible?
It's possible I think , it's the 1,0 state he talks about
Is alpha is i and beta 0 , that means there's i square chance that the system is in (1,0) and 0 chance it is in (0,1) , ie 100 % chance to be (1,0)
Or 100% chance to be detected at the 1st detector
@@Shooo117 thank you! It’s been a while since I left that comment on this but I’ll think about it
Ing. Barton
So the BS is not considered as a measurement ? Since the incoming photon doesn't have to choose between two states.
The beam splitter is the opposite of a detector. A detector forces a photon that is in a superposition of states to collapse into one of those states. A beam splitter puts a photon that is in a pure state into a superposition of pure states. So, a detector is a clarifier while a beam splitter is a confuser.
He said is there was a single beam..i would chose a single number to tell his probability to be in there.... But as there are two beam so he used two numbers
My question is why he did so
Can't we just describe it by a single number coz lets say the probability to be is beam 1 is 30% then isn't it pretty sure that probability to be in 2nd beam is 70%
You confuse probability with probability amplitude, they are different things.
What does it mean to change the phase of a photon?
Increase optical path length
delays it, or speeds it up, by an angle, usually in radians, like the phase in A.C. power, you could have a three phase system for example, with each phase being 60 degrees ahead or lagging the other? (just guessing)
Fletcher Helms Fluid theory (Reproduction/Feed/Reasoning) decanted selfover hexagon...
Fletcher Helms as functions Reproduction/Feed/reasoning.... what's not Reproduction/Feed is reasoning...
He said is there was a single beam..i would chose a single number to tell his probability to be in there.... But as there are two beam so he used two numbers
My question is why he did so
Can't we just describe it by a single number coz lets say the probability to be is beam 1 is 30% then isn't it pretty sure that probability to be in 2nd beam is 70%
Fluid theory (Reproduction/Feed/Reasoning) decanted selfmultidimentionalover...
I want this board...🥲🤧