The "weirdness" of entanglement comes from the observation that measuring one entangled particle appears to "fix" the state of the other entangled particle regardless of distance.
I like the experiments with entangled photons with opposite polarization.
If one passes through a horizontal filter (50% probability of passing, like any ordinary photon) then you know that the other one will pass through a vertical filter (theoretically 100% probability of passing) and be absorbed by a horizontal filter (theoretically 0% probability of passing).
I like the experiments with entangled photons with opposite polarization.
If one passes through a horizontal filter (50% probability of passing, like any ordinary photon) then you know that the other one will pass through a vertical filter (theoretically 100% probability of passing) and be absorbed by a horizontal filter (theoretically 0% probability of passing).
Even ones delayed by billions of years by gravitational lensing. I'm not bothered at all by these experiments, the pop science extrapolating this to "entangled" massive objects is generally based on ignorance.
Well, yeah, as long as there is no irreversible interaction with the entangled particles their position in space just doesn't matter.
The easiest way to get ones head around it, I think, is to simply look at two entangled particles as one unit and disregard the spatial separation.
I've never seen entanglement with larger objects, but interference (see double-slit experiment) seems to have been demonstrated with molecules consisting of up to 60 carbon atoms.
Luckily there is decoherence, or our world would look very different. Even a free electron will decohere (what a beautiful word) in a billionth of a second under standard ambient temperature and pressure. For larger objects there is just no chance in hell to achieve entanglement under such conditions. Even just gravity might be enough to make this impossible for larger objects.
I also regularly see people being confused about "observation". It's not that human observation has anything to do with it, but that a physical measurement, such as forcing a photon through a polarization filter, changes the state of the system - an irreversible interaction.
An easy way to confirm this is to simply raise the temperature in a double-slit experiment. At some point the temperature is high enough for the particle to decohere before passing the slits.
You can observe all you want, at some point the interference will simply go away.
The easiest way to get ones head around it, I think, is to simply look at two entangled particles as one unit and disregard the spatial separation.
I've never seen entanglement with larger objects, but interference (see double-slit experiment) seems to have been demonstrated with molecules consisting of up to 60 carbon atoms.
Luckily there is decoherence, or our world would look very different. Even a free electron will decohere (what a beautiful word) in a billionth of a second under standard ambient temperature and pressure. For larger objects there is just no chance in hell to achieve entanglement under such conditions. Even just gravity might be enough to make this impossible for larger objects.
I also regularly see people being confused about "observation". It's not that human observation has anything to do with it, but that a physical measurement, such as forcing a photon through a polarization filter, changes the state of the system - an irreversible interaction.
An easy way to confirm this is to simply raise the temperature in a double-slit experiment. At some point the temperature is high enough for the particle to decohere before passing the slits.
You can observe all you want, at some point the interference will simply go away.
Last edited:
What's not appreciated by folks thinking classically is that the states truly ARE in superposition before measurement. It isn't like the envelope analogy mentioned before where the states are already determined, you just don't know what they are until you open one of the envelopes. In a quantum system, the states truly are not determined before observation.
This is a tough concept to wrap one's mind around.
This is a tough concept to wrap one's mind around.
Yeah no that analogy misses the point that you need to do a measurement and that this has consequences, unlike just looking at a macroscopic letter.
In the entangled photons with opposite polarity example I mentioned this is actually very easy to see.
The probability of a photon passing a polarization filter is cos(angle)^2.
Now if the angles of the entangled photons were determined then the left one could have 40°, the right one 130°, with the left having a probability of 57% to pass the horizontal filter, same for the right to pass the vertical filter:
cos(40°)^2 = 0.57
cos(130°-90°)^2 = 0.57
But that means that we should see situations where e.g. the left photon first passes, but then the right one does not.
But in QM if the left one is determined to be horizontal then the right one has to be vertical and has to pass.
In the entangled photons with opposite polarity example I mentioned this is actually very easy to see.
The probability of a photon passing a polarization filter is cos(angle)^2.
Now if the angles of the entangled photons were determined then the left one could have 40°, the right one 130°, with the left having a probability of 57% to pass the horizontal filter, same for the right to pass the vertical filter:
cos(40°)^2 = 0.57
cos(130°-90°)^2 = 0.57
But that means that we should see situations where e.g. the left photon first passes, but then the right one does not.
But in QM if the left one is determined to be horizontal then the right one has to be vertical and has to pass.
The one that I don't get is that in quantum data encryption (I was told this by a physicist involved in a local startup) if there is future possibility of observation the encryption collapses. I hope I got that right, the example was something like a "leak" in an optical comms link.
What I meant was that in a professional paper such as a thesis, Einstein only talk about concept and Math, not really about its application or interpretation of life phenomena. I don't have a problem with the concept, but when about application/interpretation it starts to become illogical. Problem is, most of these are not from Einstein himself.
With application/interpretation, I mean something like this:
I will read again about time dilation. I think I didn't found anything wrong with the core concept. But I disagree with most interpretation I read.
Exactly the opposite. Why not carefully read his introductory book on relativity? It's remarkably accessible, and that may disabuse you of some very wrong ideas.
https://www.ibiblio.org/ebooks/Einstein/Einstein_Relativity.pdf
Different interpretation can be in how the clock can be slowed down (it can be mechanical). Or interpretation of "clock". What is a clock. Is a broken clock a clock. Does a clock has a reference. Is this reference a singular.
Or even velocity can be interpreted differently. In Physics velocity doesn't have direction (as opposed to speed). So particle moving in straight line, in circle or vibrating can be interpreted as having velocity, even tho their effects can be different.
Or what is a gravity. It's a big mystery.
Jay, you may want to step back a bit and get a better basic grasp of Newtonian mechanics before tackling relativity. There's a profound difference between accelerated and constant-velocity frames, and it's important to be able to recognize which is which. It will also give you a better appreciation of the beautiful correspondence between Newtonian and relativistic mechanics.
Given that the latest atomic clocks are so accurate they will diverge if one is a foot above the other not sure how much more evidence you need.
Agreed Gravity is an odd one. Actually all of general relativity is odd.
It's off topic, and way beyond my maths comprehension, but the standard model worries me. Maxwell's equations are simple and beautiful, even to a thicky like me and explain electromagnetism to all but Jack Bybee and the snake oil crew. The standard model was similar until they realised that there was no mass. Adding mass makes it a muddly mess (to my thicky mind).I can't help thinking there must be a neater solution. I would love to understand that area more.
Actually I have been going back and forth. Hopefully with better interpretation in every cycles. But I'm not a type that can retain knowledge or detailed information for a long time (besides, that is not my approach to learning).
And I supposed to have my certification exam in Physics today but with no preparation (last day notice) I decided to skip it for a reason:
I have joined several tests and certifications (cross subjects). Rarely I didn't end up at the top of the chart even with thousands of participants. What I'm trying to say is... I have no problem with learning and understanding...
I may be wrong... but it is not about having difficulty to understand. I may be mistaken in thinking that I understand... I may be mistaken in thinking that others are wrong... But that's the point, it's different.
Not really and a broken clock certainly does not count because it does not tick accurately ...
In the theoretical "proof" the clock is basically a light pulse traveling between two mirrors with a detector on one side. Given the speed of light and distance traveled you know the time that passed for each tick.
This time increases when we observe a relatively moving clock, because the distance is longer.
Practically people use atomic clocks, which also slow down. Mechanical clocks also would work, but are way too crude and inaccurate for typical experiments.
Of course a clock has a reference, otherwise it would not be a clock but some random ticking device.
In the light clock it is the speed of light, in atom clocks it's electronic transition of the electromagnetic spectrum of atoms.
The most accurate clock, afaik, is a Strontium clock that uses optical transitions and is said to be so accurate that you can see a change if you just elevate it a few centimeters on Earth (due to gravitational time dilation).
Ahm, maybe you should start studying the basics of physics first before going anywhere near relativity...
Wow.
"The more we know, the more we don't know". Whatever it is supposed to mean
. But as long as we don't understand the universe, we don't know anything...- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.