What is Entangled: Definition and 270 Discussions

Entangled, 2004, is an abstract sculpture created by Indiana-based artist Brose Partington (American b. 1979). The sculpture is located on the Indiana University-Purdue University Indianapolis (IUPUI) campus at the Herron School of Art and Design, 735 W. New York Street in Indianapolis, Indiana, in the United States. It was given to Herron by Ezra Freidlander and Linda H. Freidlander in 2005.

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  1. J

    I How to distinguish between diagonal vs horizontal/vertical polarization?

    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...
  2. P

    I Is there a generator of entangled photons with fixed polarization?

    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...
  3. Dr Wu

    Entangled by Quantum Supremacy

    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...
  4. Marilyn67

    I Mach-Zehnder interferometer, but with an entangled beam?

    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...
  5. S

    I Are the proton and electron quantum entangled in the hydrogen atom?

    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.
  6. Marilyn67

    I Construction of an Entangled Photon Source

    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...
  7. R

    B Does DCQE show a shift between the two "which path" results?

    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...
  8. L

    I Why Does Quantum Entanglement Seem Puzzling Compared to Everyday Correlations?

    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...
  9. Christian Thom

    I Double-slit experiment with momentum entangled pair of photons

    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...
  10. B

    B Entangled particle decoherence question

    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...
  11. H

    A Entangled particles in curved spacetime

    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...
  12. C

    B Tardigrade is first multicellular organism to be quantum entangled

    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...
  13. S

    I Interference of signal photons entangled with idlers

    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...
  14. BillTre

    B Understanding Entangled Particles in Different Time Frames

    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...
  15. S

    I Do I have entangled mittens?

    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...
  16. nomadreid

    I Entangled particles in black hole decay?

    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...
  17. docnet

    B Entangled protons in a uniform magnetic field?

    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?
  18. Jerome71

    B Do entangled particles always react in an anti-symmetric way?

    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
  19. L

    B How do you tell when particles are or aren't entangled?

    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...
  20. I

    I Mixed states from entangled state

    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...
  21. M

    B Are photons entangled with a component of the atom that emitted them?

    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?
  22. C

    I Are entangled particles really separated?

    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...
  23. O

    I Bell's Inequality => 4 entangled Photons impossible?

    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...
  24. H

    I Information diagram for entangled particles?

    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...
  25. R

    I Measuring Entangled Particles in two different Basis

    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 =...
  26. R

    I Measurement of an entangled Particles in two Different Bases

    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 =...
  27. CarawayBlossom

    I Measurement of Entangled Particles causes up or down spin?

    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...
  28. Leonardo Muzzi

    I Quantum Eraser: do entangled photons arrive at different moments?

    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...
  29. allisrelative

    I Does Decoherence get rid of all Quantumness?

    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...
  30. Souma

    I The "size" of entangled particles

    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...
  31. A

    B Can entangled electrons in helium be observed and measured in practice?

    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.
  32. K

    I Steering the polarization of entangled photons

    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...
  33. S

    I Trying to Generate Entangled Photons

    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...
  34. nomadreid

    I Quantum state variable for entangled system

    (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...
  35. jackmiller2003

    I Time Delay Information Transfer with Entangled Particles

    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...
  36. Quantum Alchemy

    B Can entangled particle pairs be measured at the same time?

    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...
  37. P

    I Can you locally tell that a measurement you made was entangled?

    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...
  38. B

    B Can quantum entangled particles be split and sent into a black hole

    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...
  39. muonion

    I Do spin operators 'appear' to commute for an entangled spin state?

    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...
  40. Joseph1785

    B Do Entangled Photons React to possible Photon-Photon Collisions?

    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...
  41. remormalise

    I Unveiling the Mystery of Entangled Particle Spin

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

    B Entangled Photons: Adam Becker's QM Book "What is Real?

    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...
  43. S

    B Does Entangled Particle Detection Prove the Spooky Action at a Distance?

    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...
  44. B

    I Phase shift after double-slit for entangled photons

    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}...
  45. B

    Quantum state of entangled photons

    Homework Statement Suppose two polarization-entangled photons A and B in the following Bell state: \begin{equation} \Phi=\frac{1}{\sqrt{2}}\bigl(\left|H_{A},H_{B}\right\rangle + \left| V_{A},V_{B}\right\rangle\bigr) \end{equation} 1. What is the state if the photon A passes through a...
  46. Auto-Didact

    Quantum Entangled Living Bacteria

    "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...
  47. R

    B Understanding Entangled Electrons: Creation, Isolation, and Observation

    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...
  48. Robert Friz

    B Are Quantum Entities in Macro Sized Objects Entangled?

    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...
  49. J

    B Are all particles and photons entangled?

    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?
  50. F

    A Entangled wave function solved perturbatively

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