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

Complementarity and the Afshar Experiment

Tabish Qureshi

Published Jan 16, 2007• 6 citations
OpenAlex

Abstract

A modified two-slit interference experiment, proposed and carried out by Shahriar Afshar [first reported by M. Chown, New Scientist {\\bf 183}, 30 (2004)], claims to demonstrate a violation of Bohr's complementarity principle. We point out the flaw in Afshar's analysis and show why complementarity is robust and cannot be violated in any experiment which is a variant of the conventional two-slit experiment.

Related papers

Afshar's Experiment does not show a Violation of Complementarity

Steuernagel, O

A recent experiment performed by S. Afshar [first reported by M. Chown, New Scientist {\\bf 183}, 30 (2004)] is analyzed. It was claimed that this experiment could be interpreted as a demonstration of a violation of the principle of complementarity in quantum mechanics. Instead, it is shown here that it can be understood in terms of classical wave optics and the standard interpretation of quantum mechanics. Its performance is quantified and it is concluded that the experiment is suboptimal in the sense that it does not fully exhaust the limits imposed by quantum mechanics.

•Dec 15, 2005•18 citations

Modified Two-Slit Experiments and Complementarity

Tabish Qureshi

Some modified two-slit interference experiments claim to demonstrate a violation of Bohr’s complementarity principle. A typical such experiment is theoretically analyzed using wave-packet dynamics. The flaw in the analysis of such experiments is pointed out and it is demonstrated that they do not violate complementarity. In addition, it is quite generally proved that if the state of a particle is such that the modulus square of the wave-function yields an interference pattern, then it necessarily loses which-path information.

arXiv:quant-ph/0701109•Journal of Quantum Information Science•Jan 1, 2012•9 citations

Modified Afshar experiment: calculations

Eduardo V. Flores

The Afshar experiment is a relatively simple two-slit experiment with results that show a discrepancy with the predictions of Bohr's Principle of Complementarity. We report on the results of a calculation using a simpler but equivalent set-up called the modified Afshar experiment. Numerical results are in agreement with the experimental measurements performed on the Afshar experiment set-up. Calculations show that the level of which-way information and visibility in the Afshar experiment is higher than originally estimated.

arXiv:0803.2192•Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Aug 20, 2009•5 citations

The Afshar Two-Slit Experiment and Complementarity

Ruth E. Kastner

A modified version of Young's experiment by Shahriar Afshar demonstrates that, prior to a ``which-way'' measurement indicating which slit a particle goes through, an interference pattern exists. It has been claimed that this result constitutes a violation of the Principle of Complementarity. This paper discusses the implications of this experiment and considers how Cramer's Transactional Interpretation accomodates the result. It is shown that the Afshar experiment is isomorphic in key respects to a a spin one-half particle prepared as ``spin up along x'' and post-selected in a specific state of spin along z. It is concluded that Bohr would have had no more problem accounting for the Afshar result than he would in accounting for the aforementioned pre- and post-selection spin experiment, in which the particle's preparation state is confirmed by a nondestructive measurement prior to post-selection.

•Feb 2, 2005•0 citations

BOHR'S COMPLEMENTARITY AND AFSHAR'S EXPERIMENT: NON-DUALISTIC STUDY AT THE SINGLE-QUANTUM LEVEL

C Ravi Kumar, Nakka Gurappa

Using a newly proposed `wave-particle non-dualistic interpretation' of the quantum formalism, Bohr's principle of complementarity is analyzed in the context of the single-slit diffraction and the Afshar's experiments - at the single-quantum level. The fundamental flaw in the Afshar's argument is explicitly pointed out.

•Jan 1, 2019•0 citations

No Paradox in Wave–Particle Duality

Andrew Knight

The assertion that an experiment by Afshar et al. demonstrates violation of Bohr’s Principle of Complementarity is based on the faulty assumption that which-way information in a double-slit interference experiment can be retroactively determined from a future measurement.

•Jan 1, 2020•3 citations
A modified two-slit interference experiment, proposed and carried out by Shahriar Afshar [first reported by M. Chown, New Scientist {\bf 183}, 30 (2004)], claims to demonstrate a violation of Bohr's complementarity principle. We point out the flaw in Afshar's analysis and show why complementarity is robust and cannot be violated in any experiment which is a variant of the conventional two-slit experiment.
A recent experiment performed by S. Afshar [first reported by M. Chown, New Scientist {\\bf 183}, 30 (2004)] is analyzed. It was claimed that this experiment could be interpreted as a demonstration of a violation of the principle of complementarity in quantum mechanics. Instead, it is shown here that it can be understood in terms of classical wave optics and the standard interpretation of quantum mechanics. Its performance is quantified and it is concluded that the experiment is suboptimal in the sense that it does not fully exhaust the limits imposed by quantum mechanics.
Some modified two-slit interference experiments claim to demonstrate a violation of Bohr’s complementarity principle. A typical such experiment is theoretically analyzed using wave-packet dynamics. The flaw in the analysis of such experiments is pointed out and it is demonstrated that they do not violate complementarity. In addition, it is quite generally proved that if the state of a particle is such that the modulus square of the wave-function yields an interference pattern, then it necessarily loses which-path information.
The Afshar experiment is a relatively simple two-slit experiment with results that show a discrepancy with the predictions of Bohr's Principle of Complementarity. We report on the results of a calculation using a simpler but equivalent set-up called the modified Afshar experiment. Numerical results are in agreement with the experimental measurements performed on the Afshar experiment set-up. Calculations show that the level of which-way information and visibility in the Afshar experiment is higher than originally estimated.
A modified version of Young's experiment by Shahriar Afshar demonstrates that, prior to a ``which-way'' measurement indicating which slit a particle goes through, an interference pattern exists. It has been claimed that this result constitutes a violation of the Principle of Complementarity. This paper discusses the implications of this experiment and considers how Cramer's Transactional Interpretation accomodates the result. It is shown that the Afshar experiment is isomorphic in key respects to a a spin one-half particle prepared as ``spin up along x'' and post-selected in a specific state of spin along z. It is concluded that Bohr would have had no more problem accounting for the Afshar result than he would in accounting for the aforementioned pre- and post-selection spin experiment, in which the particle's preparation state is confirmed by a nondestructive measurement prior to post-selection.