Entangled Definition and 268 Threads

If we entangle particles and separate them by a large distance, can the action of measuring one cause decoherence at the other's location? If yes then does this violate relativisitic causality? Could we not use this process to transmit information instantaneously? If no then why not? Is there...

We know that can't measure both position and momentum simultaneously whether both are orthogonal. If i measure position one entangled electron and momentum on other electron for single state then how Heisenberg's uncertainity princple works?? so We may know the both parameter.

Hello all, I have been searching and trying to find out how entanglement is detected experimentally, but I have a few sticking points. Initially I just want to know the principles behind the experiments. In summary this is how I understand it so far. 1. Entangled photons produced eg in pairs...

This should be a very easy question to answer, but oddly enough I'm not certain what that answer is. So I thought that someone here could help me. It's easy enough to visualize and understand a pair of entangled particles, and how measuring the state of one instantly effects the state of the...

I am trying to understand how it may be possible to maintain two particles in an entangled superposition. Is this possible or has this already been done?

I'm having trouble finding comprehensible explanations of how experimenters can ever know that two particles are entangled. I understand that the first experimental confirmation of entanglement used Calcium or Mercury vapor which when excited gave off pairs of entangled photons. But how did...

Hello all! I'm trying to wrap my head around this quantum entanglement thingy. As far as I have understood, if you have two entangled particles, say two electrones, it is impossible to predict their spins since they are thought to be in superposition of both up and down. But if you measure...

Are electrons in the, say lowest energy level, shell, of an atom, always entangled? i.e. Do electrons (in a shell) have to be necessarily entangled? Is there any maths (law of conservation of spin/momentum etc) that says so? Any relation with Pauli's exclusion principle?

I mean, which is the operational mechanism? Is it deterministic? I mean, can I "grab" two particles and make them entangled or the process is random and I can only make a lot of them and filter only the ones that get entangled? My idea is that, perhaps, by knowing how it happens in real life...

Hello there! I´ve tried searching the internet but seems to be in need of a heavy book for this answer. I stumbled upon this forum and decided I would love to ask some Experts here :-) Basically what attributes are quantum entangled? I know that spin is, but is fx kinetic energy? Are...

Entangled photon-pairs are being produced in labs with 'Spontaneous Parametric Down Conversion' apparatus. While in the core of our sun gamma photons are being produced through nuclear fusion which then down-converted into myriad of low-energy photons. Is it possible that those myriad of...

Hi folks --- I was just reading that entangled states are very much the norm in the universe. Can anybody tell me why entanglement is taken to be such a pervasive feature of the world, so that product states are the exception? Has it got something to do with the fact that strictly speaking all...

what does position entangled mean (physically)? The below is an attempt to understand position entanglement. It may require a lot of corrections and modifications. Look forward to your responses. A photon (A) would have a probability distribution, so would it's entangled twin/photon (B). The...

It just occurred to me that I don't know why composites of interacting particles are always in entangled -- as opposed to mere product -- states. Obviously if they are not interacting we will just represent them as being in a product state; but why is it that being in a product state entails...

I have seen four two qubit entangled states of the form: $ \frac{1}{\sqrt{2}} \left | 00 \right > \pm \left | 11 \right >$ $ \frac{1}{\sqrt{2}} \left | 01 \right > \pm \left | 10 \right >$ I want to write a most general two qubit entangled state. I presume it can be of the form: $...

Although it is well known that a series of individual photons will build up an interference pattern in a double slit setup, there have been few (if any) experiments where such a pattern is built up by sending photons through one at a time. Here is a great experiment from one of the top quantum...

Why is Schrodinger's Cat entangled? Or is it not? I recently saw a poster on deviantart that said this: http://browse.deviantart.com/art/WANTED-Schrodinger-s-Cat-130508078 It said it was in a superposition, that i get, but the entanglement? That i don't get. -QuantumPixel

Hi, I'm quite new to quantum mechanics, learning about it in my free time in a life-long learning fashion :) I've been trying to find a solution to a problem for some time, and the results I included below appear to be OK, but I have doubts about the method I used, so any help or guidance...

can particles be entangled on any property having more than two states? Photons can be entangled on spin. however spin has only two states: Up or down, plus or minus So the question is: is there any property (having more than two states) on which photons/electrons/bucky-ball can be...

Why do (we assume that) entangled particles (say photons/electrons) have to be in an indeterminate state?

...sent one into a black hole?

I'm sure this has been asked a million times, but how do we know that entangled particles don't "choose" their states when they're separated? If possible, choose the most basic example. Thanks!

Regarding the polarization correlation studies generated using parametric down conversion. All the studies appear to be done correlating the polarization of linearly polarized photons. Has any experiment been done showing the same effect with circularly polarized light? 1) If this...

What happens when you take two entangled particles and put one on a spaceship that moves close to the speed of light? Now you measure one of the two particles. The state of the other should become decided at the exact moment you do the measurement. But there is no absolute simultaneity if you...

Could a Fermion be Entangled with a Boson ?

Let's say you have entangled particles emitted from a source. What happens if you measure the spin of both entangled particles simultaneously with respect to the reference frame of the source? Would the spins measured still be opposite (anti-correlated)? Would you even get a definite...

Consider the simplest of all possible atoms: A hydrogen atom with only a proton as its nucleus. According to QFT, the electron is constantly exchanging photons with the proton. So, are the electron and proton entangled? Thanks in advance.

If everything came from the same singularity prior to the Big Bang, are we still entangled? If yes could we retrieve information of the whole Universe from one single particle? If not when and how were we de-entangled?

what does it mean to be momentum entangled? and how can it improve resolution? what does it mean to be momentum entangled? - say for photons and how can it improve the resolution of an optical microscope? Understanding polarization entanglement is easier/familiar - i.e. - the twins have...

can a particle/photon be quantum entangled on more than one property/factor? (at the same time-- redundant phrase(?)) for example can two photons be entangled along say - a) spin AND momentum b) position and momentum c) spin and position d) polarization and spin

I am confused about the the notation |ab> for an entangled pair. Isn't this the same as the tensor product |a> \otimes |b>? If so, I run into another confusion when using the corresponding matrices. I read that I should apply a Hadamard operator H twice to the input state |01>. Does this mean...

There is something that has been bothering me recently: that is, the distinction between a separable state and being part of an entangled state. To make my query concrete, consider: \left|\psi\right\rangle = \alpha \left|0\right\rangle + \beta \left|1\right\rangle and...

Entangled particles are used in various experiments for example: DCQE (delayed choice quantum eraser) Bells tests Mach Zehnder (modified) DCES (delayed choice entanglement swapping - Ma) Now, one out of a trillion photons, on average, gets entangled after passing through the SPDC (?)...

Homework Statement I've been asked to find out if are entangled states or not Homework Equations I thought an entangled state was one where a measurement of one qubit revealed the nature of the other qubit in the state The Attempt at a Solution If I am correct in my definition of an...

If we have two groups of photons; each group consisting of two entangled photons. We allow one of the photons from each group to interact with another object. If we perform a polarisation measurement on each photon of one group, will the photons in the other group, independent of whether...

When you create a pair of entangled photons, are they simultaneously in a superposition of V and H, and 45 and 135 polarisations?

As an amateur, I have been reading about the EPR argument, and afterwards Quantum Entanglement recently. Then I thought that the bound between two particles is only the applicability of a physical rule of everyday reality. For instance, the momentum or energy must be preserved at all times, so...

Hello everyone, I've got a quick question... Given two entangled photons, going through a polarization filter with relative angle a, what is the correlation between the two "answers" (whether the photon is blocked or let through)? I believe it's either cos(a) or cos^2(a), but I'm not sure...

Consider the maximum inner product of a density operator with a maximally entangled state. (So, given a density operator, we're maximizing over all maximally entangled states.) I'm pretty sure the minimum value (a lower bound on the maximum) for this is 1/n2, using the density operator 1/n2...

Given two entangled particles, and the spin of both is measured along two separate axes making an angle of "a", what is the correlation between the two? So how much of the particles will give the same "answer" to the spin measurement? I've tried googling, but the answers I did find were...

http://physicsworld.com/cws/article/news/31068 I thought only elctrons could be entangled but now atoms and even ions can be entangled. Would this suggest that it could work its way to the macro levels. Could two diffrent rocks or soccer balls become entangled?

Quick question: Do entangled photons have opposite spin? If so, how do we know? I mean I know that they should because of conservation of angular momentum. But Cos(0)^2 = Cos(180)^2. So it looks like they’re the same. Or am I missing something.

Dear generous and helpful physicists, A number of threads here contemplate strategies for transmitting information faster than light by observing an entangled particle in one place, allegedly causing the wave function of its entangled twin to instantly collapse in another, far away place...

I'm sorry if this is a silly question and please forgive me but, if you split photons into two by any medium or matter can it entangle photons? Do the photons have to go through a beta barium borate crystal or any other crystals? Are there any alternatives to split photons? Please provide good...

Some say that there are parts but their properties depend on the whole. But if we cannot assign properties to the 'parts' of an entangled system, what can it be to be a 'part' or any kind of entity in the first place? Can we say that there are parts but that they are not independent? What can...

I'm a bit confused about quantum entanglement. First of all, how exactly do you entangle two atoms? I've heard about how they entangled atoms in quantum teleportation experiments, but I don't get how they did it. I've heard that the atoms must "interact", but what exactly does that mean? Do they...

http://en.wikipedia.org/wiki/Quantum_entanglement#cite_note-0" Is there an experiment where bucky balls are entangled? Many of us have heard about bucky balls showing single particle interference in a double slit experiment. However I have not heard of them being entangled. I read the...

Do they have to vibrate at the same frequency or something similar?

http://arxiv.org/abs/1101.2223 Abstract Even though ideas of extracting future-related, or Faster-Than-Light (FTL) information from hyperspace using quantum entanglement have generally been refuted in the last ten years, in this paper we show that the original 'Delayed Choice Quantum...

Are quarks that made up a proton or neutron naturally entangled at all times? If not. When do they lose entanglement or reestablish entanglement? If they are always entangled. How about between two protons/neutrons or more. Are they all entangled?