Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Proceedings of the Samahang Pisika ng Pilipinas

Demystifying quantum weirdness in delayed-choice quantum eraser experiment using entangled photons

Matthew Besana Dinglasan, John Paul A. Besagas, Eric A. Galapon

Published May 23, 2019• 0 citations
OpenAlex

Abstract

We have constructed the full density matrix for the quantum eraser experiment using two entangled photons in [Y. Kim et al., Phys. Rev. Lett. 84, 1 (2000)] by tracing the evolution of the initial entangled state to its final state when it reaches the different detectors. Several projective measurements were made on the full density matrix of the entangled system to exhibit the presence or absence of interference fringes which corresponds to the availability of the which path information. The results of the projective measurements agree with the experimental results. Therefore, all the information that can be accessed in the quantum eraser eraser experiment can be obtained in the full density matrix of the system and it is only a matter of postselecting the data points to exhibit the presence or absence of interference fringes.

Related papers

Delayed-choice quantum eraser for the undergraduate laboratory

James M. Ashby, Peter D. Schwarz, Maximilian Schlosshauer

In a delayed-choice quantum eraser, interference fringes are obtained by erasing which-way information after the interfering particle has already been irreversibly detected. Following an introductory review of delayed-choice experiments and quantum erasure, we describe the experimental realization of an optical delayed-choice quantum eraser, suitable for advanced undergraduates, based on polarization-entangled pairs of single photons. In our experiment, the delay of the erasure is implemented using two different setups. The first setup employs an arrangement of mirrors to increase the optical path length of the photons carrying which-way information. In the second setup, we use fiber-optic cables to elongate the path of these photons after their passage through the polarization analyzer but prior to their arrival at the detector. We compare our results to data obtained in the absence of a delay and find excellent agreement. This shows that the timing of the erasure is irrelevant, as also predicted by quantum mechanics. The experiment can serve as a valuable pedagogical tool for conveying the fundamentals of quantum mechanics.

arXiv:1601.06089•American Journal of Physics•Jan 20, 2016•22 citations

Random Delayed-Choice Quantum Eraser via Two-Photon Imaging

Giuliano Scarcelli, Yu Zhou, Yanhua H. Shih

We report on a delayed-choice quantum eraser experiment based on a two-photon imaging scheme using entangled photon pairs. After the detection of a photon which passed through a double-slit, a random delayed choice is made to erase or not erase the which-path information by the measurement of its distant entangled twin; the particle-like and wave-like behavior of the photon are then recorded simultaneously and respectively by only one set of joint detection devices. The present eraser takes advantage of two-photon imaging. The complete which-path information of a photon is transferred to its distant entangled twin through a "ghost" image. The choice is made on the Fourier transform plane of the ghost image between reading "complete information" or "partial information" of the double-path.

arXiv:quant-ph/0512207•Dec 22, 2005•0 citations

Delayed Choice and Quantum Eraser: An Illustrated Guide Based on the Wave-or-Particle Geometric Framework

junfeng gu

The delayed-choice experiment and the quantum eraser experiment are two of the most challenging interpretive problems in quantum mechanics. Standard textbook accounts trace the presence or absence of interference to whether the experimenter "knows" the photon's path — a causal framework implying backward-in-time influence. This article offers an intuitive, diagram-rich account grounded in the wave-or-particle geometric framework, revealing that both experiments share a far simpler backbone: interference depends solely on how many waves reach a given detector. One wave → no interference. Two waves → interference. This conclusion alters no mathematical prediction of quantum mechanics; it merely flips the causal arrow from "knowing the path destroys interference" to "the number of waves creates interference." A forthcoming main paper will present the complete three-column correspondence (experimental step → geometry → QFT standard) with full algebraic verification.

•Aug 2, 2026•0 citations

Taming the Delayed Choice Quantum Eraser

Johannes Fankhauser

I discuss the delayed choice quantum eraser experiment by drawing an analogy to a Bell-type measurement and giving a straightforward account in standard quantum mechanics. The delayed choice quantum eraser experiment turns out to resemble a Bell-type scenario in which the resolution of the paradox is rather trivial, and so there really is no mystery. At first glance, the experiment suggests that measurements on one part of an entangled photon pair (the idler) can be employed to control whether the measurement outcome of the other part of the photon pair (the signal) produces interference fringes at a screen after being sent through a double slit. Significantly, the choice whether there is interference or not can be made long after the signal photon encounters the screen. The results of the experiment have been alleged to invoke some sort of backwards in time influence. I argue that this issue can be eliminated by taking into proper account the role of the signal photon. Likewise, in the de Broglie–Bohm picture the trajectories of the particle can be given a well-defined description at any instant of time during the experiment. Thus, it is again clear that there is no need to resort to any kind of backwards in time influence. Quanta 2019; 8: 44-56.

arXiv:1707.07884•Quanta•Aug 11, 2019•10 citations

Demystifying the delayed-choice quantum eraser

Tabish Qureshi

Abstract The delayed-choice quantum eraser has long been a subject of controversy, and has been looked at as being incomprehensible to having retro-causal effect in time. Here the delayed-choice quantum eraser is theoretically analyzed using standard quantum mechanics. Employing a Mach–Zehnder interferometer, instead of a conventional two-slit interference, brings in surprising clarity. Some common mistakes in interpreting the experiment are pointed out. It is demonstrated that in the delayed mode there is no which-way information present after the particle is registered on the screen or the final detectors, contrary to popular belief. However, it is shown that another kind of path information is present even after the particle is registered in the final detectors. The registered particle can be used to predict the results of certain yet to be made measurements on the which-way detector. This novel correlation can be tested in a careful experiment. It is consequently argued that there is no big mystery in the experiment, and no retro-causal effect whatsoever.

arXiv:1908.03920•European Journal of Physics•May 12, 2020•17 citations

Another Quantum Eraser Experiment with Two-photon States of Light

Taesoo Kim, Jeong-Hoon Ko, Heonoh Kim

The quantum eraser experiment was revisited, using entangled photons of visible light in a Hong-Ou-Handel type interferometer with a magnitude two orders higher than before in count rates. We introduced which-path information by polarization and subsequently erasied this information by means of polarizers in front of detectors. It was found that the visibility of the interference fringe is revived from 0% to 88% as the polarizers are changed from 0 $^{\circ}$ to 45 $^{\circ}$ .

Journal of the Optical Society of Korea•Sep 1, 2002•2 citations
We have constructed the full density matrix for the quantum eraser experiment using two entangled photons in [Y. Kim et al., Phys. Rev. Lett. 84, 1 (2000)] by tracing the evolution of the initial entangled state to its final state when it reaches the different detectors. Several projective measurements were made on the full density matrix of the entangled system to exhibit the presence or absence of interference fringes which corresponds to the availability of the which path information. The results of the projective measurements agree with the experimental results. Therefore, all the information that can be accessed in the quantum eraser eraser experiment can be obtained in the full density matrix of the system and it is only a matter of postselecting the data points to exhibit the presence or absence of interference fringes.
In a delayed-choice quantum eraser, interference fringes are obtained by erasing which-way information after the interfering particle has already been irreversibly detected. Following an introductory review of delayed-choice experiments and quantum erasure, we describe the experimental realization of an optical delayed-choice quantum eraser, suitable for advanced undergraduates, based on polarization-entangled pairs of single photons. In our experiment, the delay of the erasure is implemented using two different setups. The first setup employs an arrangement of mirrors to increase the optical path length of the photons carrying which-way information. In the second setup, we use fiber-optic cables to elongate the path of these photons after their passage through the polarization analyzer but prior to their arrival at the detector. We compare our results to data obtained in the absence of a delay and find excellent agreement. This shows that the timing of the erasure is irrelevant, as also predicted by quantum mechanics. The experiment can serve as a valuable pedagogical tool for conveying the fundamentals of quantum mechanics.
We report on a delayed-choice quantum eraser experiment based on a two-photon imaging scheme using entangled photon pairs. After the detection of a photon which passed through a double-slit, a random delayed choice is made to erase or not erase the which-path information by the measurement of its distant entangled twin; the particle-like and wave-like behavior of the photon are then recorded simultaneously and respectively by only one set of joint detection devices. The present eraser takes advantage of two-photon imaging. The complete which-path information of a photon is transferred to its distant entangled twin through a "ghost" image. The choice is made on the Fourier transform plane of the ghost image between reading "complete information" or "partial information" of the double-path.
The delayed-choice experiment and the quantum eraser experiment are two of the most challenging interpretive problems in quantum mechanics. Standard textbook accounts trace the presence or absence of interference to whether the experimenter "knows" the photon's path — a causal framework implying backward-in-time influence. This article offers an intuitive, diagram-rich account grounded in the wave-or-particle geometric framework, revealing that both experiments share a far simpler backbone: interference depends solely on how many waves reach a given detector. One wave → no interference. Two waves → interference. This conclusion alters no mathematical prediction of quantum mechanics; it merely flips the causal arrow from "knowing the path destroys interference" to "the number of waves creates interference." A forthcoming main paper will present the complete three-column correspondence (experimental step → geometry → QFT standard) with full algebraic verification.
I discuss the delayed choice quantum eraser experiment by drawing an analogy to a Bell-type measurement and giving a straightforward account in standard quantum mechanics. The delayed choice quantum eraser experiment turns out to resemble a Bell-type scenario in which the resolution of the paradox is rather trivial, and so there really is no mystery. At first glance, the experiment suggests that measurements on one part of an entangled photon pair (the idler) can be employed to control whether the measurement outcome of the other part of the photon pair (the signal) produces interference fringes at a screen after being sent through a double slit. Significantly, the choice whether there is interference or not can be made long after the signal photon encounters the screen. The results of the experiment have been alleged to invoke some sort of backwards in time influence. I argue that this issue can be eliminated by taking into proper account the role of the signal photon. Likewise, in the de Broglie–Bohm picture the trajectories of the particle can be given a well-defined description at any instant of time during the experiment. Thus, it is again clear that there is no need to resort to any kind of backwards in time influence. Quanta 2019; 8: 44-56.
Abstract The delayed-choice quantum eraser has long been a subject of controversy, and has been looked at as being incomprehensible to having retro-causal effect in time. Here the delayed-choice quantum eraser is theoretically analyzed using standard quantum mechanics. Employing a Mach–Zehnder interferometer, instead of a conventional two-slit interference, brings in surprising clarity. Some common mistakes in interpreting the experiment are pointed out. It is demonstrated that in the delayed mode there is no which-way information present after the particle is registered on the screen or the final detectors, contrary to popular belief. However, it is shown that another kind of path information is present even after the particle is registered in the final detectors. The registered particle can be used to predict the results of certain yet to be made measurements on the which-way detector. This novel correlation can be tested in a careful experiment. It is consequently argued that there is no big mystery in the experiment, and no retro-causal effect whatsoever.
The quantum eraser experiment was revisited, using entangled photons of visible light in a Hong-Ou-Handel type interferometer with a magnitude two orders higher than before in count rates. We introduced which-path information by polarization and subsequently erasied this information by means of polarizers in front of detectors. It was found that the visibility of the interference fringe is revived from 0% to 88% as the polarizers are changed from 0 ∘^{\circ}∘ to 45 ∘^{\circ}∘ .