Entangled Definition and 268 Threads

I have been working for some time on designing an experiment and have gotten stuck on one particular aspect. I would greatly appreciate any advice that can be offered. I'm using SPDC to produce two polarization-entangled photons. Through the course of the experiment I know that one of the...

Hello everyone! I don't know where to look for information - maybe here it will work :) Is there a generator of entangled photons with fixed polarization? If not, is it theoretically possible to build or is it against the laws of physics. I need this knowledge for further computer...

The many online articles about the future security issues posed by quantum supremacy — at least those pitched at the interested layperson (like myself) — tend for quite understandable reasons to focus on the outcomes that QS will have on today’s digital-based security systems. . . not as they...

Hello, The Mach-Zehnder interferometer makes it possible to highlight the corpuscular and undulatory aspect of light, (in particular using single photons). By using the "continuous" beam from a coherent source, one is able to visualize directly on two screens E1 and E2, an interference pattern...

The proton and electron are described by separate wavefunctions. When they come together in the hydrogen atom are they quantum entangled and have a joint wavefunction.

Hello, Happy New Year 2023 ! Interested in spontaneous parametric down-conversion (SPDC), and the possibility of creating entangled photon pairs, I studied several possible configurations with type 1 and type 2 nonlinear crystals. When using these crystals, the dominant phenomenon is second...

The Delayed Choice Quantum Eraser (DCQE) experiment attempts to show that which-path information can be "erased," and interference recovered. I'll refrain from explaining the experiment, and assume you are familiar with the setup. I refer to the Wikipedia page about it, and the original Kim...

Suppose someone throws coins and once they fall on heads or tails, she saws them along the middle on two parts: one pointing towards the ground and the other pointing from the ground. Then she sends those two parts into opposite directions so after some time they reach two distant planets, one...

In Kaur, M., Singh, M. Quantum double-double-slit experiment with momentum entangled photons. Sci Rep 10, 11427 (2020). https://doi.org/10.1038/s41598-020-68181-1 and in C. K. Hong and T. G. Noh, "Two-photon double-slit interference experiment," J. Opt. Soc. Am. B 15, 1192-1197 (1998) it is...

Suppose there are two entangled particles A and B, separated by a few miles or light years. If the spin for particle A is observed, then from my understanding, A will experience quantum decoherence. And now we can be sure that B will have the opposite spin since B is entangled with A. Assuming...

i do not know if the question about entangled particles has found mainstream answers; Suppose that pairs of maximally entangled particles are shared by Bob and Alice in a time independant gravitational field. Bob measures the spin in the direction of far fixed stars. There is a direction in...

https://www.newscientist.com/article/2302337-tardigrade-is-first-multicellular-organism-to-be-quantum-entangled/ A tardigrade has been quantum entangled with a superconducting qubit – and lived to tell the tale. It is the first time a multicellular organism has been placed in this strange...

Consider the following experiment: A photon hits a beam splitter, then a non-linear crystal (nichtlinearer Kristall - sorry, prepared the image in German) on each path that does parametric down conversion, splitting the photon into a signal and an idler. The idlers proceed to two detectors (D1...

Here is something I don't understand which I expect someone here can explain. If one member of an entangled pair goes on a trip at relativistic speeds, there will be two different frames of observation, with two different elapsed times. The time frames can get off-set by years, over a long...

In my messy apartment I might well find a right-hand mitten, and immediately know the left-hand state of its missing partner. A classical description works just fine for this (their opposite states were produced at the time of manufacture) and I don't need to consider my observation of one...

First, I was not sure whether this should go into the Relativity or the Quantum Physics rubric, but since the central question is about entanglement, I opted for the Quantum. I do not have the necessary sophistication to follow string theory arguments, and even most explanations in...

In NMR, protons that are near each other exchange energy with each other by photon emission and absorption. Proton A is spin down, and proton B is spin up. proton A emits a photon and becomes spin up, and proton B absorbs this photon and becomes spin down. have the two protons been entangled?

I am a non scientist and nonetheless a have the following question: once particles are (intrinsically) entangled do they always react in the opposite way/ anti-symetric to each other? Source https://www.physicsforums.com/forums/quantum-physics.62/post-thread

I'm trying to get my head around the principles of quantum entanglement (would love to get some schooling on the issue but I don't have that kind of money) and trying to discern the actual science from the horrible misconceptions is difficult. I know you can't transmit information faster than...

I'm an undergrad in physics, and have been asking myself the following question recently. Suppose you have a pure quantum state p (von neumann entropy=0), made of 2 sub-states p1 and p2 that are entangled. Because they are entangled, p \neq p1 x p2. Hence the entanglement entropy of p (=0) is...

If an atom were made to release a Photon, then a number of the components of the atoms nucleus were theoretically extremely quickly removed. would the previously emitted photon change wave length?

I would greatly appreciate answers or perspective on these questions, thank you in advance! Since entangled photons are traveling at the speed of light relative to our spacetime, my understanding is that they experience no time or distance from the moment they are generated to the moment they...

Correlation between polarization measurements of entangled photons at angles less than 45 are greater than classically statistically possible. No set of hidden variables can be preordained to explain the 75% correlation of photon measurements at 30 degrees and complete anticorrelation of...

Hi Pf I read that when two particles are maximally entangled , all the information is in the correlations between the particles. If we need 1 bit to describe one particles. Are two bits in the correlations? three particles may be entangled and then we need to considere 3 bits. As entanglement...

Consider two entangled spin half particles given by the generic form of Bell Equation in Z-axis: ##\psi = (a\uparrow \uparrow + b\downarrow \downarrow)## where ##a^2+b^2=1## In a (2D) planer rotated (by an angle ##\theta##) direction the new equation can be given by: ##|\psi \rangle =...

Consider two entangled spin half particles given by the generic form of Bell Equation in Z-axis: ##\psi = (a\uparrow \uparrow + b\downarrow \downarrow)## where ##a^2+b^2=1## In a (2D) planer rotated (by an angle ##\theta##) direction the new equation can be given by: ##|\psi \rangle =...

In reading around, it seems that in the case of entangled particles, it is the measurement of one of the particles that causes the other one to be it's opposite spin and that there's some means of info transfer going on caused by the measurement. I'm not understanding why it would not be that...

Considering a Delayed Choice Quantum Eraser experiment such as the one in the picture above: It is said that paired photons arriving at the detectors A,B,C,or D, reach the detectors after the entangled pair has reached the interference screen. Are we actually able to measure the time interval...

The answer is no and even when decoherence occurs for Wigner's Friend in the lab, quantum coherence remains. Let's start with the paper that illustrates this. Assisted Macroscopic Quantumness CONT. https://arxiv.org/abs/1711.10498 Wow, I recently read this paper and the results are simply...

Hello everyone, I hope you are having a nice day, I was reading [The principles of Quantum Mechanics by P.A.M Dirac], and I was attracted to the definition of size. The book says: "If the object under observation is such that the unavoidable limiting disturbance is negligible, then the object...

If you measure the location of an electron in helium, does it impact the expectation value for the location of the other? Also, can this experiment be conducted in practice? Thanks.

The following is a diagram of an EPR thought experiment using photons that uses the same type of components as described in this paper http://www2.optics.rochester.edu/~stroud/cqi/rochester/UR19.pdf Would you detect any photons at the right detector? I want to be convinced one way or another...

I've been trying to generate entangled photons using KTP laser pointer that normally produces green light at 532 nm. I was hoping that after removing the IR filter, I could add a reflective coating (right now the coating I have is a glittery metallic green nail polish) to reflect the green light...

(This question is on the elementary side...) In the Schrödinger picture, the state is dependent on time. If you have a state composed of several particles, generally you can break them up, with each one depending on local time. But in an entangled system, say of two particles, you can no longer...

Hello, my name is Jack and I'm a year 11 student in Australia. After listening to, and reading some information regarding quantum entanglement, I'm still a little unsure about the solution to a thought experiment: Let's say that I create a situation in which multiple pairs of particles are...

Has there been an experiment where 2 particles that are entangled are measured at the same time? If so what was the result? Can any observer occupy the same frame of reference down to an electron? Don't we all exist at different times based on our frame of reference so none of us can share the...

Suppose you make a measurement of some particle. If you know it is entangled, you may have conditional knowledge of measurements that might be made at a spacelike distance (if the other observer does/has done x, they will/did get result y). Note, I am using local in the sense of special...

I am new here so apologies in advance. When a virtual particle and anti particle appear at the event horizon of a black hole, before they destroy each other, they are split with one being sucked into the black hole and the other becoming exhaust. Are these the same particles as the quantum...

Let's consider Bohm's paradox (explaining as follows). A zero spin particle converts into two half-spin particles which move in the opposite directions. The parent particle had no angular momentum, so total spin of two particles is 0 implying they are in the singlet state. Suppose we measured Sz...

Summary: The limitations of engagement and possible results of the Breit-Wheeler theory collider in relation. *You will need to read the article for this to make sense Upon reading an article "Scientists discover how to turn light into matter after 80-year quest" I had a thought, How will...

If you change the spin of an entangled particle without knowing its original spin, what happens to the other entangled particle?

I'm reading Adam Becker's QM book "What is Real?" At one point he says: "The single wave function shared by the two entangled photons guarantees that they will always behave in the same manner when encountering two polarizers with parallel axes. It does not specify what they will do. But merely...

My question about quantum entaglement is: is a Quantum particle's spin [altered] into another spin position at the moment of detection or is it just a 'snapshot picture' of the spin at the moment of detection (without alteration)? It seems this is an important differentiation. If there is no...

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}...

"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...

I am reading and trying to understand “Spooky Action,” an article that has been published in Scientific American, December, 2018, starting on page 60. To begin: 1) How does one create a pair of entangled electrons, especially with spin sideways? 2) How does one then isolate one electron from...

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...

1) are all particles/photons theoretically entangled at birth but we just never or will know? Or is it under specific conditions? 2) how much of the photons that the sun emits entangled particles/photons?

Can the wave function for entangled particles be solved perturbatively? Are there virtual processes involved with this? Thanks again.

It seems that the entanglement of two particles does not change with time and can cross long distanced as long an neither particle decoheres with the environment. This makes me wonder if the wave function for that entanglement can have any time or space dependence? I only did a brief search for...