What is Quantum eraser: Definition and 112 Discussions

In quantum mechanics, the quantum eraser experiment is an interferometer experiment that demonstrates several fundamental aspects of quantum mechanics, including quantum entanglement and complementarity.
The quantum eraser experiment is a variation of Thomas Young's classic double-slit experiment. It establishes that when action is taken to determine which of 2 slits a photon has passed through, the photon cannot interfere with itself. When a stream of photons is marked in this way, then the interference fringes characteristic of the Young experiment will not be seen. The experiment also creates situations in which a photon that has been "marked" to reveal through which slit it has passed can later be "unmarked." A photon that has been "marked" cannot interfere with itself and will not produce fringe patterns, but a photon that has been "marked" and then "unmarked" will interfere with itself and produce the fringes characteristic of Young's experiment.

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  1. H

    I Is it possible for a BBO crystal to produce an interference pattern?

    This question originated under a separate thread (see below) in an attempt to better understand what is happening with the quantum eraser experiment. Specifically, it seems that the BBO crystal which splits the photon beam after the double slit is critical in how the experiment is setup...
  2. H

    I Delayed quantum eraser: turning off sensor to bring back interference

    I've been learning about the delayed-choice-quantum-eraser experiment. To sum up; I imagine a double slit which has behind it a crystal which splits photons into entangled pairs. The crystal sends a photon to the right, from either slit, toward a single sensor (s1) which simply measures that a...
  3. A

    I Delayed Choice Quantum Eraser with altered beam splitter

    Hi People, In Kim's real setup for interference patterns we use a beam splitter as 50:50 (reflectance,transmittance rate), lets assume we use 20:80 (%20 reflectance, %80 transmittance) for beam splitter what could we observe in this situtation on detectors (except D3,D4)? Dont forget we use...
  4. A

    I Delayed choice quantum eraser setup with no beam splitter

    Hello Dear Physicists, I know this question probably discussed many times before. But I need a clear answer about this setup in case there is no beam splitter. What is gonna happen in this situation? My classical intuitions say I will see a correlated interference pattern on both screens(or...
  5. Halc

    I Hossenfelder: Delayed Choice Quantum Eraser, Debunked?

    I have found serious errors in Sabine's videos before which has damaged my trust in her presenting peer-reviewed information. I'm pretty sure I'm wrong about this one, but can't figure out where. The video is here: www.youtube.com/watch?v=RQv5CVELG3U']www.youtube.com/watch?v=RQv5CVELG3U The...
  6. S

    I Query on use of prism in delayed choice quantum eraser experiment

    Hi. I’ve seen a number of schematic diagrams for the Delayed Choice Quantum Eraser experiment. Some include a prism to make the two idler photon paths diverge. However, the prism is shown refracting the ‘idler rays’ in a way which contravenes Snell’s law. E.g. see prism marked ‘PS’ (not the...
  7. Strilanc

    I [video] Simulating a delayed choice quantum eraser in an online drag-d

    This is a follow-up video I made to a previous one on common misconceptions about the experiment. I'm interested in people's opinions here about how close the simulated experiment is to the real thing (e.g. there have to be some compromises due to the simulator not having free space propagation...
  8. G

    B Quantify Quantum Eraser Experiment

    I'm trying to grasp a quantum eraser experiment as described in a book I read. It helps me to put numbers to things, so my goal is to calculate the amount (intensity) of the light that demonstrates interference. The author describes a double slit quantum eraser experiment using polarized light...
  9. Erik Ayer

    I Understanding Coherence vs. Entanglement in Quantum Eraser

    As I understand it, either coherence or entanglement can be in an experiment or some of each, varying continuously between the two. Because of this, coincidence detection is needed to pick out interference patterns among all the data. Coherence would refer to quantum waves of photons taking...
  10. Erik Ayer

    I Question on circular polarization and the quantum eraser

    Looking at the wikipedia page for the (original) quantum eraser (https://en.wikipedia.org/wiki/Quantum_eraser_experiment), quarter-wave plates in front of the slits change photons from being linearly polarized to being circularly polarized. I think this is the case when there is no polarizer in...
  11. L

    B Does Quantum Eraser Prove That Intention Does Not Create Physical Reality?

    If you perform a double slit experiment but never look at the results could we say that the experiment never actually happened? The beginning of the experiment would show intention to find results but we believe intention does not create physical reality. Quantum Eraser could be preventing us...
  12. johnconner

    I Copenhagen interpretation & Delayed-choice quantum eraser

    For explaining Delayed-choice quantum eraser experiment, what if I change the Copenhagen interpretation a little. When the experiment is concluded, we observe one detector (the first detector with the shortest path) has detected the pattern long before the wavefunction is collapsed (before the...
  13. 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...
  14. R

    I Parametric down-conversion and double-slits

    I'm fascinated by the delayed-choice quantum eraser (DCQE) experiment from Kim et al. 1999. As I understand from the paper, the observer at the signal beam detector d0 (the screen) never sees an interference pattern, but the "lump" sum of all possible outcomes at the idler photon detectors...
  15. A

    I Classical treatment of quantum eraser?

    The below experimental setup is of the sort one finds frequently discussed in the delayed choice quantum eraser (QE) experiments, such as that of Kim et al. (https://arxiv.org/abs/quant-ph/9903047) I extracted only the essential part I'm wondering about and did not find a satisfying answer in...
  16. G

    I Delayed-choice quantum eraser experiment

    In the Kim's experiments (see picture below) part of the downwards photons are involved in a quantum eraser and part aren't. In D0 (upward path) we see interference if the entangled photons (downward path) are detected in D1 or D2 and we don't see interference if the entangled photons are...
  17. S

    I Kim's 1999 delayed-choice quantum eraser experiment

    As I understand the delayed-choice quantum eraser experiment, first performed by Kim in 1999, entangled photons are used to determine which-way data, and the which-way data is obtained by virtue of where the entangled particles land, as opposed to using a measuring device that may be collapsing...
  18. Erik Ayer

    I Can the quantum eraser work without coincidence?

    I understand that downconverted light is not coherent, so that there are essentially many overlapping interference patterns and that coincidence detection filters out one of those patterns. However, could the downconverted light be filtered such that interference can be detected without...
  19. B

    B Quantum eraser and time travel

    i don't understand, how does quantum eraser not imply time travel? i firmly don't believe in retrocausality, but it really does seem to imply it . can someone please explain in layman terms? in here paul davies says observers now can "constrain" the past, does this mean our perception of...
  20. nomadreid

    I Can the quantum eraser experiment produce two different interference patterns?

    In the explanation of the quantum eraser, Wikipedia https://en.wikipedia.org/wiki/Quantum_eraser_experiment states "...the 'which-path' information is 'erased,' whereupon the interference pattern is recovered. (Rather than removing or reversing any changes introduced into the photon or its path...
  21. B

    I Quantum eraser in Bohmian Mechanics and many worlds theory

    All the literature on the quantum eraser that I've seen is grounded in the Copenhagen interpretation of quantum mechanics. It's very easy to understand the experiment in those terms. Do you know how quantum eraser experiments are interpreted by the de Broglie–Bohm theory? What is erased in this...
  22. S

    B Delayed Choice Quantum Eraser Experiment Results

    Hello everyone. I want to ask some questions about dcqe experiments results which are bugging my mind. It is so hard to find reliable sources in my native language so I'm here. Also sorry for my scuffed english. Assuming we all know the famous experiment setup, I am directly passing to the...
  23. Phillane

    I Delayed Choice / Quantum Eraser Experiment Question?

    Hello, Disclaimer: I have read other posts and understand it is important to reference ‘sources’ and that popular science articles / videos can be a source of annoyance. However, I am struggling to: A. Find an answer to my question, and/or B. Understand if my question is even valid. I hope...
  24. T

    I Exploring the Quantum Eraser Experiment: Debunking Popular Misconceptions

    I keep hearing in pop science that the quantum eraser experiment shows that the interference pattern emerges again if the data of the photon is deleted. I suspect what is really going on is that the scientists did something to the photons to affect their paths so that it cannot be determined...
  25. A

    B Delayed Choice Quantum Eraser - Experimental Details

    What exactly happens during the time gap between the detectors being activated, and the eraser subsequently wiping out the information after the results screen has received the photons? For example, do we "observe" the interference pattern being absent and then (gradually or immediately)...
  26. B

    I Data from a delayed choice quantum eraser experiment

    Hello! Does anyone here have raw data from a delayed choice quantum eraser experiment that you wouldn't mind sharing? Ideally, data from all the detectors, not just coincidence counts that the analysis usually focuses on? Or, are you aware of any data repository where data from quantum physics...
  27. rnk

    I Delayed choice quantum eraser - partial information retrieval

    In Delayed choice quantum eraser experiment (https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser) entangled photons are sent on different paths. They reach their detectors at different times. The one arriving early is called a signal photon. The photon that arrives at its destination at...
  28. L

    I Question about Delayed Choice Quantum Eraser

    As almost everybody knows, DCQE experiment only shows interference after the data analysis, never in the first instance, regardless of future events for idler photons. https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser So, my question is, why you cannot see interference with this...
  29. G

    I Delayed choice quantum eraser with actual 'choice'?

    Hi. The Wikipedia article on the delayed choice quantum eraser is mostly about Kim's experiment where there's IMHO not really a 'choice' about the erasure of the path information, at least not by the experimentators. Have such experiments also been performed where this choice is more...
  30. E

    I A question about the delayed choice quantum eraser experiment

    This delayed choice quantum eraser experiment captured my attention and after deep thought about it, I find it really startling and totally punishing to my common sense. My question is: Can you predict the future, say, a human's mind, using the quantum eraser? I imagine a modified version of the...
  31. G

    I Mandel quantum eraser: No signal/idler-correlations needed?

    Hi. I found slightly different depictions of the Mandel quantum eraser experiment (1991). They are all from German sources, but I think they are pretty clear nonetheless. The first is from a German schoolbook: The second is from here: They claim that interference appears when the origins...
  32. G

    I What destroys interference: Possibility or actual measurment?

    Hi. If we place two perpendicularly oriented linear polarizers at a double slit, there will be no interference pattern. In the wave picture, this is trivial: Two waves with perpendicular polarization cannot interfere. In a quantum picture, I've often seen the interpretation that the sheer...
  33. T

    I Unraveling the Quantum Eraser Mystery

    hi guys, I'm new to this beautiful forum and i signed up to ask a question that drives me nuts for weeks. I am german so my english sucks but, i learned about this experiment with the quantum eraser. basically the experiment goes like this. you shoot photons through a double slit and behind the...
  34. S

    B About the delayed choice quantum eraser experiment

    Hey, I was watching this video About the quantum eraser experiment (I suggest you watch too, so we would be speaking in the same terms). As I understand it, The experiment goes such that: first the photon enters through the slits as a superposition, then the photon gets measured to gain...
  35. V

    I Delayed choice quantum eraser -- Again....

    Hello. This topic seems to be discussed a lot of times before. But I still have some questions which was not clarified earlier and I will be grateful if someone will give me explanations :) First of all, to define a context, original experiment setup: (source...
  36. Cobalt101

    I Understanding the Delayed Choice Quantum Eraser Experiment

    I've been reading Brian Greene's "The Fabric of the Cosmos" and am currently at the description of the delayed choice quantum eraser experiment. My understanding is that this can be set up so that the idler photons can be measured (long) after the signal photons hit the detector screen. Under...
  37. 0

    I Delayed choice quantum eraser scanning telescope

    Hi! :) I have this question regarding delayed choice quantum eraser - If my understanding is correct then interference pattern will form/not form based on whether there is erasing mirror in path of entangled particle - regardless of time when particle arrive at mirror. Should not it be...
  38. 0

    I Delayed Choice Quantum Eraser Question

    I watched this video that dumbs down and explains very simply how the quantum eraser works From my understanding: The particle will go thru both slits if not observed (probably wave collapsed). If you setup a device that will detect it (that emits a photon if the particles passes thru) the...
  39. O

    I Delayed choice quantum eraser

    Hi, I have a simple question regarding this experiment: If we were to place a new detector, say D5, immediately after BSa, would it mean that D0 never shows an interference pattern for D5? I think so, as it would seem this should be no different than the result obtained at D3, but just want to...
  40. L

    B Delayed choice quantum eraser experiment interference pattern question

    If I understand the delayed choice quantum eraser experiment correctly, it's essentially set up in the manner as the double slit. The only difference is that the detectors are set up in front of the double slits. It was thought that if there was an interference pattern that appeared then that...
  41. Strilanc

    Criticize diagram of delayed choice quantum eraser

    I'm trying to create a simplified diagram of the delayed choice quantum eraser experiment (contrast with the confusing one on Wikipedia and the simplified one on some random site). Here's what I have so far: Context that goes with the diagram: it is understood that an entangled pair of...
  42. gjonesy

    Delayed choice quantum eraser question

    Hello I have a question just out of curiosity...suppose you set up a delayed choice quantum eraser experiment and the technologies were available to super miniaturize your detectors, and instead of having a single double slit you have several double slit walls set up in alignment that are ultra...
  43. Dadface

    Delayed choice quantum eraser by Kim et al.

    Hello I have been looking at the results published by Kim et Al and am a little bit baffled by one of the graphs shown in fig 4. which shows the single detector counting rate of Do. The rate is very approximately constant across the whole range and averages about 280000 counts per second. Very...
  44. SpaceKidd_N7

    Delayed Choice Quantum Eraser: Am I missing something here?

    Hello everyone, I actually have three questions: 1. Am I missing an important detail in my understanding of how the delayed choice quantum eraser experiment is done? 2. How does one account for what takes place in the experiment without using the concept of "retrocausality" (effect before...
  45. A

    Misc. Is this a valid DIY quantum eraser?

    Hi, I found this video and there is some argument about the experiment being legit, can anyone with enough understanding of quantum mechanics comment on that? Thank you!
  46. K

    I Implications of the Delayed Choice Quantum Eraser

    My mind was blown upon discovering this experiment. Subsequent attempts at putting my brain back together have all failed miserably. All posts trying to demystify the experiment have either appeared flawed or were too complex for my primitive liberal arts brain to understand. Now I fear such...
  47. andrewkirk

    Kim's delayed choice quantum eraser -- Is it really delayed?

    I have been mulling over various aspects of delayed quantum erasure and came upon the following puzzle. It is about the famous 'delayed choice quantum eraser' of Kim, Kulik, Shih and Scully. The paper says (1st para of 2nd column on p2) that the path length from the BBO crystal that generates...
  48. andrewkirk

    Mathematics of entanglement in quantum erasers

    I am trying to understand the mathematics of quantum eraser experiments, in order to deepen my understanding of what is really happening. The paper I am currently working on is: "A double-slit quantum eraser" by S. P. Walborn, M. O. Terra Cunha, S. Padua, and C. H. Monken (2001) in which a...
  49. G

    Indivisible units of time and the quantum eraser experiment

    If we take an indivisible unit of time (a Planck time perhaps), could the possible retro-causality hinted at in the Quantum Eraser Experiment be a process where the retro-causality goes back along the same plank unit rather than back in time per se Metaphor - I don't travel to a different train...
  50. A

    Understanding Quantum Eraser Experiments

    I would like to start a discussion about the most basic principles behind quantum eraser experiments. I understand this has been debated here many, many times and for some of you there is nothing to talk about, but I still find it interesting and would like to get some of your opinions. I know...
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