Quantum entanglement is a physical phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the group cannot be described independently of the state of the others, including when the particles are separated by a large distance. The topic of quantum entanglement is at the heart of the disparity between classical and quantum physics: entanglement is a primary feature of quantum mechanics lacking in classical mechanics.
Measurements of physical properties such as position, momentum, spin, and polarization performed on entangled particles can, in some cases, be found to be perfectly correlated. For example, if a pair of entangled particles is generated such that their total spin is known to be zero, and one particle is found to have clockwise spin on a first axis, then the spin of the other particle, measured on the same axis, is found to be counterclockwise. However, this behavior gives rise to seemingly paradoxical effects: any measurement of a particle's properties results in an irreversible wave function collapse of that particle and changes the original quantum state. With entangled particles, such measurements affect the entangled system as a whole.
Such phenomena were the subject of a 1935 paper by Albert Einstein, Boris Podolsky, and Nathan Rosen, and several papers by Erwin Schrödinger shortly thereafter, describing what came to be known as the EPR paradox. Einstein and others considered such behavior impossible, as it violated the local realism view of causality (Einstein referring to it as "spooky action at a distance") and argued that the accepted formulation of quantum mechanics must therefore be incomplete.
Later, however, the counterintuitive predictions of quantum mechanics were verified in tests where polarization or spin of entangled particles was measured at separate locations, statistically violating Bell's inequality. In earlier tests, it couldn't be ruled out that the result at one point could have been subtly transmitted to the remote point, affecting the outcome at the second location. However, so-called "loophole-free" Bell tests have been performed where the locations were sufficiently separated that communications at the speed of light would have taken longer—in one case, 10,000 times longer—than the interval between the measurements.According to some interpretations of quantum mechanics, the effect of one measurement occurs instantly. Other interpretations which don't recognize wavefunction collapse dispute that there is any "effect" at all. However, all interpretations agree that entanglement produces correlation between the measurements and that the mutual information between the entangled particles can be exploited, but that any transmission of information at faster-than-light speeds is impossible.Quantum entanglement has been demonstrated experimentally with photons, neutrinos, electrons, molecules as large as buckyballs, and even small diamonds. The utilization of entanglement in communication, computation and quantum radar is a very active area of research and development.
http://arxiv.org/abs/0905.1119
Relativity as a Consequence of Quantum Entanglement: A Quantum Logic Gate Space Model for the Universe
Authors: John S. Hamel
(Submitted on 7 May 2009 (v1), last revised 14 May 2009 (this version, v2))
Abstract: Everything in the Universe is assumed to be...
1. I have previously stated my opinion that Bohmian Mechanics (BM, or dBB), insofar as it is a hidden variable theory (HV), must be non-contextual. On the other hand, most Bohmians consider BM to be contextual in order to satisfy the requirements of Bell, Kochen-Specker (KS), etc.
It seems...
Yea, so I was thinking...the no hair theorem says that you can only know 3 things about the matter inside black holes - mass, angular momentum, and charge right? But what if I create a pair of entangled particles, and throw one of them into a black hole...will I then know information about that...
A thought exercise:
You have entangled particles, leave one on Earth and put the other on a spaceship that is moving close to the speed of light. What happens when you change the rotation of one particle or the other? Given that the speed of light is the speed limit to the universe and that...
Yes, entanglement has gone mainstream (if it wasn't already) with an article in the 5/6/2009 Wall Street Journal on the subject:
Science, Spirituality, and Some Mismatched Socks : Researchers Turn Up Evidence of 'Spooky' Quantum Behavior and Put It to Work in Encryption and Philosophy
The...
Hey guys, hope your all well. Was wondering what people make of the claims made in the paper 'Disproofs of Bell, GHZ, and Hardy Type Theorems and the Illusion of Entanglement' by Joy Christian ( http://arxiv.org/abs/0904.4259 ) where he claims ''An elementary topological error in Bell's...
Just a quick question regarding the sources used for investigating entanglement (of photons). There are two types of production method as I understand it:
('Fundamentals of quantum optics and quantum information', Peter Lambropoulos, David Petrosyan, 2006, Springer): Page 242
"In fact...
like a link that describes an entanglement experiment from start to end or something like that. I am just learning this quantum stuff, and i understand what happens AFTER theyre entangled but not HOW they get that way. do you just select 2 particles at random, put them in a jar, boom theyre...
i was watching a video on this and supposedly if an electron was on the other side of the universe it would response instantly to another electron moving.. this didnt make any sense at all because it was spoken as knowledge when there's no way that could be known... so can someone please...
Whenever i read or watch something on entanglement all they seem to talk about is the spin states of electrons. And i am confused, does whatever happen to one, the opposite happens to the other or can the same thing happen to both due to entanglement. Does entanglement go further than spin...
I have read statements which basically suggest that nuetrino oscillation prohibits any strict statement of conservation of lepton number. Is this true or is it possible that nuetrinos produced along with electrons, muons and taus become entangled so that lepton number is still strictly...
I have recently been studying the topic of Entanglement, the process of so called "teleportation." A friend of mine and I have taken a huge interest in the teleportation area and when I came across a paper on the internet and read about the Innsbruck Experiment and such, I was confused. I...
Hello, another graduate school advising situation.
Well, like everyone else (almost), i am interested in possibility of TOK and the like;
however, since I am more of a humian empiricist I typically become bitterly skeptical of String-theory and Branes and such. Since in my opinion those...
My friend just gave me a good thought experiment involving quantum entanglement violating special relativity that I can't seem to refute.
There are two immortal people A and B. A and B synchronize their clocks far away from any gravitational influence (say spot Y). B departs for spot(at an...
In this months edition of Scientific American, the main article is on how entanglement violates Special Relativity as it allows for the seemingly instantaneous transmission of information (which spin the other particle has etc.). I asked my physics teacher about this and he said that he did not...
I'm only just beginning to really learn about entanglement, and I just have some questions about what entanglement actually means.
Let's say we have one electron and put it in a magnet field. We find out what it's spin was along one axis based on whether a photon is emitted. But now we know...
Every layman discussion of entanglement usually evolves around Bell's photon experiment. But could somebody give a deeper explanation of what is meant by entanglement? (Not afraid of math!)
Hello,
could someone please tell what mistake I am doing by the following gedankenexeperiment.
Imagine two Stern-Gerlach-like devices that measure spin projections of some spin-1/2 particles. Right between them in the middle there is some trap (I don't care about technical details)...
Does an Alics-Bob scenario include entropy, and does it increase if they both determine correct states?
What if they don't? Is knowing an entanglement exists an expectation? Is measuring it a probability?
So if there's expectation and probability (or maybe there isn't). is there information...
Hi, it's my first time to post here.
I'm wondering how we can define "entanglement" for identical particles.
More simply, when two bosons are in the following state
( |psi (x) >|phi (y) > + |psi (y) >|phi (x) > ) ,
are they entangled or not?I have (at least) two ideas:
1. We can define...
I'm new to this, so I can only express and understand simple language (as far as quantum mechanics is concerned). Please try to keep the replies as less technical as possible.
Consider a simple example: Two particles ( A and B ) are ejected in opposite directions, entangled in a way such that...
Hi guys,
I am curious about the work done by Antoine Suarez. I think this is a famous one but I need some more information about this. He concluded :
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The final results
The final results of the experiments with moving...
It is said that quantum entanglement cannot transmit information between two points faster than light because the observed states are random. Assuming classical information theory, it's clear that if I measure photon A as 'up', than its entangled partner B must be in state 'down'. A prediction...
The experimental constructs designed to test entanglement (Alain Aspect et al) via Bell's theorem, have always made me question the interpretation of the evidence.
I understand the reasoning behind the tests as follows:
The experimental findings are considered evidence of the (conjugate)...
I'd like to confirm my understanding from one year ago, that the following is possible:
1) Using a combination of entanglement processes (entangling an already entangled particle with another already entangled particle, such that the outer particles, the other particles of each pair, will be...
FTL communication: might QM entanglement "trump" relativity?
As we presently understand entanglement, it can't be used for FTL communication, since some speed-of-light exchage of information between Bob and Alice is required. So c apparently still remains the communication speed limit.
But...
Chemical bonds and quantum entanglement
I have a very basic understanding of quantum mechanics and chemistry, so please bear with any misunderstandings I may have. My question is this: what does QM have to do with the bonding between atoms in a molecule or compound? Can these bonds be labelled...
Entanglement HELP!
I can't find a decent, heuristic explination for entanglement anywhere. Wikipedia is both pedantic and pretentious on the subject.
Can someone on this message board with a good, solid understanding of entanglement please give a heuristic, non-mathematical explination? I know...
So first off, Ill admit I've forgotten most of the finer details of the bell inequality so I apologize if I've gotten something wrong.
From how I remember it, the bell inequality is a test of any local hidden variable theory vs. QM. It uses the fact that the inequality measured if a classical...
Hello,
I'm wondering how the two slit experiment interacts with entanglement. Here's an ascii art picture of the standard two slit experiment:
| |
| | #...
So, I've heard at least a couple of theories as to why individual photons continue to act as a wave as seen in the twin slit experiment, but none of them really seemed to lock down a specific answer.
So please excuse my ignorant perspective on this when I theorize that the photons continue to...
I've heard that if two particles are entangled, and one of them is run through a polarizing beam splitter, the beam can be recreated and the entanglement continues. What are the implications of this? Is there actually any use? Thanks
On General Measure of Entanglement
Hi, sirs
My major is computer science. While I currently need to deal with some physical problems. Thank you very much for your help.
It is well-known that Von Neumann entropy is a measure of entanglement for bipartite pure states. However, I...
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Ok so if two particles are entangled and I choose to measure particle A, then the entanglement is finished. But what if I measure both A and B with photons of the exact same energy; is there now a new...
I haven't seen a paper which answers this particular question, maybe someone else has... (I have scanned the preprint archive but to no avail so far).
Most Bell tests use polarizing beam splitters (PBS) to check photons at Alice and Bob. Typical are 2 detectors at Alice and 2 at Bob...
According to the newspaper Students at Geneva
University have found that "A signal passing
between entangled photons 18 km apart must
travel at least 10000 times faster than light"
Its the same problem about the 'speed' of wave function
collapse - there is no 'speed' parameter in the wave...
In photon polarization placing a horizontal polarizer in a beam of randomly polarized photons allows only half the photons through.
Question 1: Say, you have twin beams of entangled photons orthagonally polarized. If you place a horizontal polarizer in a one beam does it cut the intensity of...
Recently, an experiment in the Canary Islands demonstrated that messages could be sent using Quantum Entanglement over a distance of 144km. Since I took courses in both Relativity and Quantum Mechanics, this confuses me, since the presence of distance between the two locals would cause...
I understand a wavepacket as a better description of a particle than the classical 'solid object' but is there a similar simple picture for an entangled pair?
Is it a double wave packet? Is it two joined wavepackets?
Is it one wave packet with two objects in it? Is it actually
one complex...
Entanglement "spooky action at a distance"
Why can't we think of entanglement as simply committing (without knowledge) to a random outcome, instead of "spooky action at a distance"?
Quantum entanglement’s been in the news lately. Every once in a while, a friend points out to me that quantum communication proves quantum entanglement works and faster than light communication is possible. One even pointed it out in a Michio Kaku book. But I thought quantum physics (the theory)...
Hi all! I had a question about conflict between quantum mechanics and special relativity. Before i start, let me ask you to keep the math down to a minimum. I'm currently a high school student, so I would greatly appreciate it if you could try not to use any math beyond simple calculus. I also...
I am a total novice when it comes to quantum mechanics, but I was reading up on the phenomenon of entanglement and a question arose. Theoretically, could someone take two entangled particles and put one in a black hole, using the other to observe what happens to it? Wouldn't this violate the...
Quantum Entanglement!
How "Quantum Entanglement" happens?!
As far as i know, it's one sub-atomic particle (i.e. electron) sendig data to another particle no matter the distance between them ... How does it work? and why?
And could it work between big particles, molecules, and living beings...
Given the idea that a photon experiences only one 'time-slice' from its perspective, and exists as one elongated unit that stretches from the point of emission to the point of absorption, what implications does this have on ideas of cause and effect?
I was thinking about the so-called...
I would like to know what are some examples of what two nuclei would have to experience in order to become entangled. Could being part of the same molecule yield such a state? or would they have to be, say, daughter products of a nuclear reaction, etc?
big thanks,
Mark
I'm interested in published papers, if any, addressing the issue of whether Bell type experiments can be explained simply with classical, epistomological probability theory. In particular, can the expected "quantum" result (i.e. the probability that photons A and B will both pass through their...
Greetings,
I'm trying to illustrate how nuclear fusion would "look" from the perspective of two nuclei that are quantum entangled. I have a very limited knowledge of quantum theory but I can imagine how two nuclei might be illustrated as a waveform consisting of two functions in...