Entanglement Definition and 870 Threads

I was wondering. In this example I use polarized photons, but maybe it is applicable to electrons and spin also. We can prepare two completely unentangled polarized photons, and send them in opposite directions to two detectors preceded by a filter at particular angles. Both of them will show a...

Imagine you have a single beam of polarization-entangled photon pairs where photons of each pair have opposite polarization. This beam goes to a polarizing beam splitter. Of each pair, the vertical photon passes directly through and the horizontal photon is reflected 90 degrees left. After...

Hello, I am a 40 year old Computer Scientist by education and profession. Education in general is my hobby. I am currently listening to a lecture on quantum mechanics: The Teaching Company's Quantum Mechanics Physics of the Microscopic World. Very good. So please excuse my nievity and ignorance...

An article by the University of Waterloo talks about Quantum Entanglement Harvesting and possible novel applications, such as using it to probe the structure of spacetime: https://uwaterloo.ca/institute-for-quantum-computing/news/entanglement-harvesting-vacuum So I understand that Spacetime...

Astronomers often use the speed of a QRB or other phenomena to put a maximum bound on the size of the generating object. I find the most recent of many examples in "Furiously Fast and Red: Sub-second Optical Flaring in V404 Cyg during the 2015 Outburst Peak", Gandhi et al 14 Mar 2016...

jfizzix submitted a new PF Insights post Steering: How the EPR-Paradox Fits Between Entanglement and Nonlocality Continue reading the Original PF Insights Post.

Dear PF Forum, I have a question regarding Quantum Entanglement. I don't know much about QE, but there's something that I want to know. Two particles are entangled. Blue line is the world line of Particle A See Pic 02 Particle B travels according to Green line. And at E1 Particle B's spin is...

So I was wandering why it is not possible to use quantum particles to communicate across vast distances. As I understand it we cannot send information using this as it would break the laws of physics but what I was wandering is why can't we us entangled particles in a binary why by changing the...

Somebody told me that the condition that must be met for Quantum Entanglement in a system, is that the sum of the wavefunctions of the individual particles must equal the overall wavefunction of the system. But isn't this the case anyways with any system of two particles whether they are...

Let's suppose that we have an entangled state of two systems ##A## and ##B##: $$ \frac{1}{2}\left(|\psi_1 \phi_1\rangle+|\psi_2 \phi_2\rangle \right) $$ where ##|\psi \rangle## and ##|\phi \rangle## are energy eigenstates of ##A## and ##B## respectively. However the eigenstates##|\phi_1\rangle##...

Like, how long can it last a maximum.

I understand that we can create entangled particles in the lab. But how many (non-locally) entangled particles (such as photons/polarisation or electrons/spin) exist in free nature?

So this is going to sound ridiculous, but I want to push my curiosity to the limit. Gravitational waves propogate at the speed of light, like most things in the universe. My first question is : is this propogation slowed down by anything? The Higgs field perhaps? 2nd question ; I assume that...

So quantum entanglement acts faster than light but it's not technically communication and not actually transferring "information"? Can someone explain this to me?

I've seen some articles using particle spin experiments to 'prove' that the results violate Bell's inequality and consequently local reality. I've also seen stated that the same experiments can be done using other particle attributes such as polarisation. I can see how with polarisation, you...

The green dots represent photons in an anti-bunched state, squeezed light. The red dots represent photons in a semi-bunched state, laser light The blue dots represent photons in a bunched state, thermal light The complex setups used in entanglement experiments only squeeze light in amplitude...

Quantum particles are not localized before they are observed, as shown with the Young double slit experiments and those with entangled particles. On the other side, vacuum is filled with virtual particles. Are the non-localized particles responsible for the virtual particles? or only for a part...

In entanglement, two electrons have the same spins measured at the same time. But how is same time defined, in light of special relativity's time dilation? Doesn't this mean that, from another frame of reference, they will not be simultaneous. That means, that person in point A, knows in...

We all know how classical interference of waves can be produced by the Michaelson interferometer using the beam splitter and the detectors. No other elements needed to produce classical interference of waves. Setups like this one which create quantum entanglement http://arxiv.org/abs/1212.6136...

Deborah Hearn taught physics for many years at the University of Calgary before coming to Nanaimo. She is very interested in research about physics teaching and how to make it more effective. She has had a lifelong interest in creativity in science, and its relationship to scientific discovery...

https://www.quantamagazine.org/20140416-times-arrow-traced-to-quantum-source/ QUOTE "The idea that entanglement might explain the arrow of time first occurred to Seth Lloyd about 30 years ago, when he was a 23-year-old philosophy graduate student at Cambridge University with a Harvard physics...

Is it possible to produce an entangled photon pair and be able to delay the reception times by introducing something like a fiber bragg grating which has multiple indices of refraction which propagate wavelengths at different frequencies? Or will, because of their entangled state, do some...

I've recently been reading up on quantum entanglement, and I was wondering how the no communication theorem does not rule out non locality. From my understanding the theorm proves that two entangled particles could not communicate to one another, and this is what occurs within the framework of...

A particle in a quantum harmonic oscillator can be in a superposition of energy eigenstates, and so the energy is not well-defined. However, energy is still conserved, so if I understand it correctly the "uncertainty" in the superposition's energy must be matched by uncertainty elsewhere in the...

For some time now I’ve been intrigued by the famous argument between Bohr and Einstein, and which was apparently settled when Bell’s inequality was tested in various experiments carried out by Alain Aspect. After going around and around the whole issue for a while, I don’t think I’m convinced...

What happens if I create entangled photon pairs and then pass them through a phosphorescent coating so they are absorbed and re-emitted? Is entanglement preserved? In my case, I have succeeded and created UV entangled photon pairs in my latest experiment but I could not see them with my naked...

In his book on quantum physics, "The theoretical minimum" Leonard Susskind says that if Alice and Bob get their different coins from the same Charlie who mixes them up behind his back so he won't know which coin ends up in whose hands, the coins become entangled. If Alice gets her coin from...

Consider two polarisation-entangled photons A and B fired at two polarisationfilters that are at a certain angle α. Are the probability that A is passing its filter and the probability that B is passing its filter indepedent probabilities? I am aware that is probably an incredibly stupid...

I came across an quote from a physicist so I wanted your opinion. Most physicists, Walmsley says, believe that quantum entanglement is a property present in all objects in our macro world; we just don't see it happening. "In the everyday environment, objects are connected to other objects," he...

It is said that a coherent light beam is described by a single wave because all the individual waves add up in phase to produce a single big wave. It is also said that entangled light is described by a single wavefunction...

I think this is just a quickie. I'm interested in what is assumed about entangled photons/particles before they are observed. Is it correct to assume that the photons/particles exist in all possible states simultaneously? Thank you.

Each particle has a wave associated to it according to the principle of wave-particle duality. Between two waves there is a phase difference. What is this phase difference in the case of entangled particles? 0 degrees? 90 degrees? 180 degrees? Somewhere in between?

I just read this paper and it was very interesting. The paper is called "Experimental Test of Quantum Histories" http://arxiv.org/abs/1601.02943 Here's some of an article about the paper. https://www.sciencenews.org/article/quantum-histories-get-all-tangled I have been reading a lot lateley...

Good Morning. I need some help according to how to classify the multipartite state. from my reading, the classification according to Local Unitary (LU) and stochastic local operation and classical communication (SLOCC). How the state can be classify from LU to SLOCC?

Sorry to disturb you again, but I thought of what you said in my previous questions. Dichroic mirrors, polarizers are used in the above entanglement experiment but according to their encyclopedic definition, they only filter light by color and polarization. Half-wave plates and quarter-wave...

I was doing some thinking about entanglement and other stuff and a weird thought came up. Since the whole universe, or at least the visible universe, was at one time contained in a very small and homogenous "soup" wouldn't it follow that all the resultant particles that came later would have to...

can all quantum state be entangled without any exception even if their phases don't coincide? is the term to call this mixed state entanglement accurate? does it have to do with Fourier addition? this is related to environmental entanglement... when you are shaking hands with another person...

I have a question with regards to quantum entanglement, and how it relates to the concepts of realism and locality. I am just an interested amateur who has self-studied QM in my free time, so perhaps I should first run my understanding by you first, to make sure it is accurate : the basic idea...

When I point a 5 milliwatts red laser at a pile of barium borate crystals, all I get is red speckles of scattered light. When I point a 100 milliwats blue laser at the same pile of barium borate crystals, I get blue speckles. When I point a 2000 milliwats green laser at the pile of barium borate...

I saw many of you saying in their posts that non-linear crystals like barium borate are the only means of producing entangled photons. And because they are expensive, only some of you can afford them. But I browsed the international science magazines and found this...

So I came across this paper claiming that quantum entanglement was an as yet not understood Einstein Rosen-Bridge: http://arxiv.org/pdf/1306.0533v2.pdf I have two questions pertaining to this: 1. Does the math on this paper actually check out and is this possible? 2. Since this paper...

Homework Statement Suppose R and Q are two quantum systems with the same Hilbert space. Let |i_R \rangle and |i_Q\rangle be orthonormal basis sets for R and Q . Let A be an operator on R and B an operator on Q . Define |m\rangle := \sum_i |i_R\rangle |i_Q\rangle ...

I was thinking about the superluminal speeds observed with quantum entanglement. Perhaps the particles are not really entangled, each of them just changes their spin with an in-built pseudorandom algorithm, allowing them to appear to be "in-sync" and thus entangled. This is just purely...

I'm a layman interested in quantum mechanics and I have a few questions. I'm sorry if you receive these types of questions a lot but I can't seem to find the answers. My first question lies within the Copenhagen interpretation. In the Copenhagen interpretation, is non locality or counterfactual...

Unanswered to me at least. I have read many articles, forum discussions on quantum entanglement but never found anyone discussing these questions. Here they are: 1) How do they create (mechanism) entanglement? or How 2 particles are generated entangled? 2) What are the differences (properties)...

How close must two particles get in order to become entangled? My guess would be that the polarizations of the vacuum due to the screening effect must overlap. Otherwise, they can't be said to be interacting. Is this right? Is the amount of entanglement proportional to the amount or strength of...

Could any of the experts here say whether there could be a clue here as to how to resolve the apparent paradoxes of quantum entanglement? I mean if a distance is reduced to zero, in a photon' s frame, then we should not be surprised that measurements made on one of a pair should be reflected...

In 1935 Albert Einstein, Boris Podolsky, Nathan Rosen, and Erwin Schrödinger introduced the notion of quantum entanglement. What prompted that notion and what justified their belief it was a real phenomenon?

I've been having issues understanding quantum entanglement and non-locality recently, and certain explanations that I have been told has just made the matter more confusing. The first portion of this thread will be explaining what I know and the second part will contain the questions. First...

I would like to understand basic construction of entanglement "explanation" in QED. As I understand because we talk about coincidences QED explanation necessarily involves Fock states. And Fock states are expressed using annihilation and creation operators, right?