Entanglement Definition and 870 Threads

Hi. As far as I understand the Franson interferometer, the photons are in an entangled state like $$\left|\Psi\right\rangle=\frac{1}{\sqrt{2}}\left(\left|\text{short}\right\rangle\left|\text{short}\right\rangle+\left|\text{long}\right\rangle\left|\text{long}\right\rangle\right)$$ if the setup...

Hello all, I have read that these two properties are complimentary, similar, at least in a sense, to uncertainty between momentum and position. John Cramer used what he referred to as a Sagnac Source to vary the balance between entanglement and coherence. What, physically, has to be done to...

I am re-reading paper(s) by Huw Price and Ken Wharton that present an interesting explanation of entanglement. I will see if I can paste a link, otherwise one can find them on arXiv: one is for example, “Disentangling the Quantum World”. The idea is that there could be retro-casual communication...

I have a question about quantum entanglement, I see saying that it would not be possible to communicate faster than light using this technique, but for example, and I understand that it is not the information that travels, however if for example we use the interval of the measurement and read as...

Hi everyone While learning about quantum mechanics, I became curious about the real-life experimental data. Wikipedia says that entanglement experiments require coincidence counters, because the majority of the signal received by detectors is noise. It further says, that coincidence counters...

Hi there, Question from a biologist with very poor background in physics, but willing to understand quantum physics. I think quantum entanglement shocks everyone, even if it has been proven right. I would love to know if there is any hypothesis or crazy theory out there to explain why or how...

Hi all, I'm trying to understand how to describe the quantum state of entangled photons, including their phase, if one of them encounters a double-slit. Here's a simple example: Suppose you have two polarization-entangled photons A and B in the following Bell state: \begin{equation}...

Hi, Suppose I had a pair of protons that are entangled, and one or both of those protons decayed( https://en.wikipedia.org/wiki/Proton_decay ) over time, does that mean the entanglement between the protons does not exist anymore, and would it be fair to say that the entanglement decayed over time?

"Schrödinger's Bacterium" Could Be a Quantum Biology Milestone I can't believe I'm only seeing this article now. Achieving quantum mechanical effects with large systems, especially complicated ones such as bacteria - let alone one in vivo - has been a longstanding goal in experimental QM. To...

Hi. This is my first posting on the Physics Forum so please forgive any issues as a result. I am a (reasonably educated) lay person with a strong physics interest with extensive readings -- so please be patient with my questions. :-> My questions and interest in these issues are sincere. I...

NOVA presents a show on Einstein and Quantum Entanglement:

OK, going to ask a question that I sort of know is going to be shot down but at the moment I can't make sense of this. If I send a machine/robot with a particle that is quantum entangled with another particle that is left on earth. When one particle is blue the other is red. The machine also...

Many people talking about there are similarities and common positions in quantum entaglement and superposition with entropy. I need to know about this phenomenon

Hi, In this presentation about quantum optics it is mentioned that the same quantum state |Ψ> has different expressions in different mode bases : factorized state or entangled state. This presentation is related to this video : In some way entanglement isn't intrinsic. It depend on the...

Suppose you prepare two polarization-entangled horizontally polarized photons. Scenario 1: After the first photon passes through a linear polarizer oriented at 45 degrees, it will have later a 50% probability of being measured as horizontally polarized and 50% as vertically polarized. The...

The questions concern the extension of the holographic principle to the identification of a wormhole between two black holes with negative cosmological constant and an entangled pair on its boundary, included in the conjecture known as EPR=ER ( Maldacena, Susskind). I refer to...

Suppose you have a pair of electrons in the same quantum state, and are thus spin entangled, and they absorb a pair of photons and release them at the same time. How would this affect the photons? Would the photons be entangled? Would it affect the photon spin, and if so, how would it affect the...

Are timelike entanglement and experiments demonstrating causal non-separability by quantum superposition of causal orders an indication that causal principles may not be applicable to quantum mechanics?

I’m reading in the lay literature that experiments on Bells inequality have shown that 2 entangled particles pass information simultaneously and therefore break the special relativity rule of c and therefore indicate a break from the concept of locality. I’m sure I didn’t phrase that sentence...

Why is it that nonrelativistic quantum theory (NRQT) does not have PCT, whereas QFT does? How would you characterize the collapse of the wave function in terms of PCT? What is its PCT transform? How does QFT address EPR? Many physicists universally accept the Copenhagen interpretation and...

I want to know more about quantum entanglement and I am a undergrad student in physics.Can someone suggest some research journals or articles to easily understand the concept deeply?

Hi, I read some about quantum entanglement but I don't really understand the logic behind it. If you quantum entangle 2 particles by for example colliding them and then separate them by a long distance they are both in superposition and you do not know the spin of them. Then you separate them...

Just saw this article from a highly respected research team, and thought some might enjoy seeing how the state of the art continues to develop rapidly: 12-photon entanglement and scalable scattershot boson sampling with optimal entangled-photon pairs from parametric down-conversion Han-Sen...

In most popular explanations of entanglement, the quantum information of an entangled two-particle system changes without regard to the distance between the two particles. The following paper seems (to my unprofessional eye) to be questioning this interpretation...

Do we know if entanglement between two entangled particles is completely severed after the particles interact? By interact I am generally thinking of interacting with the measurement device. Maybe another way of asking my question: In an EPR like experiment, if you put one of the entangled...

I'd like to have a simple way of describing quantum entanglement for high school students and would appreciate feedback on whether the following is accurate (enough): "One type of entanglement involves spin, where two entangled particles will always have opposite spin (coming from conservation...

A laser gun pumps one photon at a time that goes thru an SPDC process and two entangled photons are generated...photon A and photon B... Photon A is sent to Bob who has a standard DS setup located a couple of meters away from the laser pump... since the photon is in superposition of states he...

So let me preface this by saving, I am a computer programmer, not a physicist, and the main reason I became interested in quantum mechanics has a lot to do with the recent developments in quantum computing and quantum entanglement in general, although I do have a lot of curiosity about the inner...

[Moderator's note: Spin off from a previous thread since this topic belongs in the QM forum.] https://physics.stackexchange.com/questions/423835/is-time-emergent-from-quantum-entanglement It is the first answer.

Suppose we have a pair of spin entangled electrons, measured by resp. Alice and Bob. The basises of Alice and Bob make an angle of α=10°. If Alice and Bob wind up in a joint world where Alice measures ##|u\rangle##, then the probability that, in that world, Bob measures ##|d\rangle## is...

Hi everyone! Sorry for the bad English! Please, is entanglement swapping "understood" in the most famous QM interpretations? To me, it seems that any of the interpretations really helps much... Even more: I guess this event would even show that those interpretations are wrong. But of course...

Can anyone explain me ; - What is quantum entanglement and how it effects the space-time and matter in our universe??

I was just curious. Does it take a few minutes, hours or days? Has anyone here carried out an entanglement experiment? From what I understand, the results of the measurement of entangled particles go to a coincidence counter and that's where they check the results. How long is the period before...

We've just gone over the EPR paradox in class and I'm not really satisfied by the explanation of the professor and TA. Firstly, with the example of the two spins, I still don't see why measuring one spin and then knowing the other one doesn't count as information traveling faster than light...

If we consider the Unitary evolution of the wavefunction, and interpret measurements as becoming in superposition, taking it that the measurement device gets in a superposition of spin up and spin down, do two measurement devices that each measure one particle of an entangled pair become...

Hello! If the Library of Babel has 10^(2,000,000) books, does anyone think that it is possible to create a quantum state (with a quantum computer) that represents this Library? I think that in a classical way it is impossible, but in a quantum way? I find it quite interesting! What about you? :)

Hi all! Sorry for the bad english! Please, can someone help me understand the setup from "entanglement between photons that never coexisted "? So, we start with a bean from a laser, that hits a bbo crystal, makes two entangled photons (1 and 2), 1 gets measured (lets say its vertically...

There are a pair of entangled particles moving in opposite directions. A measurement is done on particle A, the wavefunction collapses randomly, you observe either spin up or spin down, A does an action at a distance on B, particle B instantly collapses to the opposite spin state, a measurement...

Hi I am interested in finding a good measure of multipartite entanglement for pure quantum states represented in the Dicke state basis. Any recommendations of notes or texts in this regard would be appreciated. I am looking to start with the most basic measure of entanglement for states...

Can someone please explain how the author, Domino Valdano, derives the percentages explaining quantum entanglement? The original post is by Thomas Ulrich. Any help would be greatly appreciated. first click on my link posted here, then once in it just scroll to the bottom of the post and...

Hi, So far I understand that when two particles are entangled measuring the state will provide the same result for both particles. But what I can't figure out: a particle has multiple properties like spin and momentum etc, are all these properties the same (or opposite), or only the one...

Earlier this week, I found a very interesting paper pop up on the arXiv headed by Joseph Eberly, a notable figure in quantum optics and entanglement. https://arxiv.org/abs/1803.04611 In it, they look at the common treatment of wave-particle duality as a tradeoff between which-slit...

I have been considering Hawkin radiation and I am puzzled about the capture of a virtual photon. Given that the escaped photon is entangled with the captured photon I do not see how the escaped photon can shed the entanglement. Can anyone help with this?

Hello, I am 12 years old in 6th grade and love physics and Quantum Physics, I would love an explanation of Quantum Physics and Topological Quantum Matter.

Let us say we have an entangled pair of photons with opposite spin, which we want to use to transmit information at a speed greater than the speed of light. One of the spins could be assigned as YES (1) and the other as NO (0). We keep one photon and send the other to the receiver. In case out...

I have a misunderstanding about the beam splitter in this experiment High fidelity entanglement swapping with fully independent sources Rainer Kaltenbaek, Robert Prevedel, Markus Aspelmeyer,Anton Zeilinger http://arxiv.org/pdf/0809.3991.pdf Part of the diagram is reproduced here Two photons...

I'm looking for work published discussing the relationship between von Neumann entropy as well as entanglement with regard to chemical reactivity in the ultracold temperature scales. An article published under the title "Ultracold chemistry and its reaction kinematics" discussed this...

I am confused about entanglement, but I am not a physicist. The concept sounds cool and I want to understand in a way so that it is familiar with what I already know. I want to know if I am interpreting this right: 1) If we have a photon that produces a pair of electron and positron, the...

Wikipedia says https://en.m.wikipedia.org/wiki/Quantum_nonlocality#Differences_between_nonlocality_and_entanglement But isn't wave function collapse nonlocal without any quantum entanglement?

Hello everyone and happy new year. I have a quick dilemma on the concept of entanglement for a two-particle system and I am looking for some clarity: Say we have particle ##A## and particle ##B##. Both particles can be in either of the two states that we call ##|\Phi>## and ## |\beta>## or in...